Merge pull request #2415 from gfoidl/allocations

Reduced intermediate allocations

src/ImageSharp/Formats/Bmp/BmpDecoderCore.cs

@@ -453,6 +453,7 @@ internal sealed class BmpDecoderCore : IImageDecoderInternals
     /// <param name="rowsWithUndefinedPixels">Keeps track of rows, which have undefined pixels.</param>
     private void UncompressRle4(BufferedReadStream stream, int w, Span<byte> buffer, Span<bool> undefinedPixels, Span<bool> rowsWithUndefinedPixels)
     {
+        Span<byte> scratchBuffer = stackalloc byte[128];
         Span<byte> cmd = stackalloc byte[2];
         int count = 0;
 
@@ -491,9 +492,9 @@ internal sealed class BmpDecoderCore : IImageDecoderInternals
                         int max = cmd[1];
                         int bytesToRead = (int)(((uint)max + 1) / 2);
 
-                        byte[] run = new byte[bytesToRead];
+                        Span<byte> run = bytesToRead <= 128 ? scratchBuffer.Slice(0, bytesToRead) : new byte[bytesToRead];
 
-                        stream.Read(run, 0, run.Length);
+                        stream.Read(run);
 
                         int idx = 0;
                         for (int i = 0; i < max; i++)
@@ -559,6 +560,7 @@ internal sealed class BmpDecoderCore : IImageDecoderInternals
     /// <param name="rowsWithUndefinedPixels">Keeps track of rows, which have undefined pixels.</param>
     private void UncompressRle8(BufferedReadStream stream, int w, Span<byte> buffer, Span<bool> undefinedPixels, Span<bool> rowsWithUndefinedPixels)
     {
+        Span<byte> scratchBuffer = stackalloc byte[128];
         Span<byte> cmd = stackalloc byte[2];
         int count = 0;
 
@@ -596,13 +598,13 @@ internal sealed class BmpDecoderCore : IImageDecoderInternals
                         // Take this number of bytes from the stream as uncompressed data.
                         int length = cmd[1];
 
-                        byte[] run = new byte[length];
+                        Span<byte> run = length <= 128 ? scratchBuffer.Slice(0, length) : new byte[length];
 
-                        stream.Read(run, 0, run.Length);
+                        stream.Read(run);
 
-                        run.AsSpan().CopyTo(buffer[count..]);
+                        run.CopyTo(buffer[count..]);
 
-                        count += run.Length;
+                        count += length;
 
                         // Absolute mode data is aligned to two-byte word-boundary.
                         int padding = length & 1;
@@ -639,6 +641,7 @@ internal sealed class BmpDecoderCore : IImageDecoderInternals
     /// <param name="rowsWithUndefinedPixels">Keeps track of rows, which have undefined pixels.</param>
     private void UncompressRle24(BufferedReadStream stream, int w, Span<byte> buffer, Span<bool> undefinedPixels, Span<bool> rowsWithUndefinedPixels)
     {
+        Span<byte> scratchBuffer = stackalloc byte[128];
         Span<byte> cmd = stackalloc byte[2];
         int uncompressedPixels = 0;
 
@@ -675,17 +678,18 @@ internal sealed class BmpDecoderCore : IImageDecoderInternals
                         // If the second byte > 2, we are in 'absolute mode'.
                         // Take this number of bytes from the stream as uncompressed data.
                         int length = cmd[1];
+                        int length3 = length * 3;
 
-                        byte[] run = new byte[length * 3];
+                        Span<byte> run = length3 <= 128 ? scratchBuffer.Slice(0, length3) : new byte[length3];
 
-                        stream.Read(run, 0, run.Length);
+                        stream.Read(run);
 
-                        run.AsSpan().CopyTo(buffer[(uncompressedPixels * 3)..]);
+                        run.CopyTo(buffer[(uncompressedPixels * 3)..]);
 
                         uncompressedPixels += length;
 
                         // Absolute mode data is aligned to two-byte word-boundary.
-                        int padding = run.Length & 1;
+                        int padding = length3 & 1;
 
                         stream.Skip(padding);
 
@@ -1286,18 +1290,18 @@ internal sealed class BmpDecoderCore : IImageDecoderInternals
             // color masks for each color channel follow the info header.
             if (this.infoHeader.Compression == BmpCompression.BitFields)
             {
-                byte[] bitfieldsBuffer = new byte[12];
-                stream.Read(bitfieldsBuffer, 0, 12);
-                Span<byte> data = bitfieldsBuffer.AsSpan();
+                Span<byte> bitfieldsBuffer = stackalloc byte[12];
+                stream.Read(bitfieldsBuffer);
+                Span<byte> data = bitfieldsBuffer;
                 this.infoHeader.RedMask = BinaryPrimitives.ReadInt32LittleEndian(data[..4]);
                 this.infoHeader.GreenMask = BinaryPrimitives.ReadInt32LittleEndian(data.Slice(4, 4));
                 this.infoHeader.BlueMask = BinaryPrimitives.ReadInt32LittleEndian(data.Slice(8, 4));
             }
             else if (this.infoHeader.Compression == BmpCompression.BI_ALPHABITFIELDS)
             {
-                byte[] bitfieldsBuffer = new byte[16];
-                stream.Read(bitfieldsBuffer, 0, 16);
-                Span<byte> data = bitfieldsBuffer.AsSpan();
+                Span<byte> bitfieldsBuffer = stackalloc byte[16];
+                stream.Read(bitfieldsBuffer);
+                Span<byte> data = bitfieldsBuffer;
                 this.infoHeader.RedMask = BinaryPrimitives.ReadInt32LittleEndian(data[..4]);
                 this.infoHeader.GreenMask = BinaryPrimitives.ReadInt32LittleEndian(data.Slice(4, 4));
                 this.infoHeader.BlueMask = BinaryPrimitives.ReadInt32LittleEndian(data.Slice(8, 4));
@@ -1470,7 +1474,7 @@ internal sealed class BmpDecoderCore : IImageDecoderInternals
         {
             // Usually the color palette is 1024 byte (256 colors * 4), but the documentation does not mention a size limit.
             // Make sure, that we will not read pass the bitmap offset (starting position of image data).
-            if ((stream.Position + colorMapSizeBytes) > this.fileHeader.Offset)
+            if (stream.Position > this.fileHeader.Offset - colorMapSizeBytes)
             {
                 BmpThrowHelper.ThrowInvalidImageContentException(
                     $"Reading the color map would read beyond the bitmap offset. Either the color map size of '{colorMapSizeBytes}' is invalid or the bitmap offset.");

src/ImageSharp/Formats/Gif/GifDecoderCore.cs

@@ -22,7 +22,7 @@ internal sealed class GifDecoderCore : IImageDecoderInternals
     /// <summary>
     /// The temp buffer used to reduce allocations.
     /// </summary>
-    private readonly byte[] buffer = new byte[16];
+    private ScratchBuffer buffer;   // mutable struct, don't make readonly
 
     /// <summary>
     /// The global color table.
@@ -249,13 +249,13 @@ internal sealed class GifDecoderCore : IImageDecoderInternals
     /// <param name="stream">The <see cref="BufferedReadStream"/> containing image data.</param>
     private void ReadGraphicalControlExtension(BufferedReadStream stream)
     {
-        int bytesRead = stream.Read(this.buffer, 0, 6);
+        int bytesRead = stream.Read(this.buffer.Span, 0, 6);
         if (bytesRead != 6)
         {
             GifThrowHelper.ThrowInvalidImageContentException("Not enough data to read the graphic control extension");
         }
 
-        this.graphicsControlExtension = GifGraphicControlExtension.Parse(this.buffer);
+        this.graphicsControlExtension = GifGraphicControlExtension.Parse(this.buffer.Span);
     }
 
     /// <summary>
@@ -264,13 +264,13 @@ internal sealed class GifDecoderCore : IImageDecoderInternals
     /// <param name="stream">The <see cref="BufferedReadStream"/> containing image data.</param>
     private void ReadImageDescriptor(BufferedReadStream stream)
     {
-        int bytesRead = stream.Read(this.buffer, 0, 9);
+        int bytesRead = stream.Read(this.buffer.Span, 0, 9);
         if (bytesRead != 9)
         {
             GifThrowHelper.ThrowInvalidImageContentException("Not enough data to read the image descriptor");
         }
 
-        this.imageDescriptor = GifImageDescriptor.Parse(this.buffer);
+        this.imageDescriptor = GifImageDescriptor.Parse(this.buffer.Span);
         if (this.imageDescriptor.Height == 0 || this.imageDescriptor.Width == 0)
         {
             GifThrowHelper.ThrowInvalidImageContentException("Width or height should not be 0");
@@ -283,13 +283,13 @@ internal sealed class GifDecoderCore : IImageDecoderInternals
     /// <param name="stream">The <see cref="BufferedReadStream"/> containing image data.</param>
     private void ReadLogicalScreenDescriptor(BufferedReadStream stream)
     {
-        int bytesRead = stream.Read(this.buffer, 0, 7);
+        int bytesRead = stream.Read(this.buffer.Span, 0, 7);
         if (bytesRead != 7)
         {
             GifThrowHelper.ThrowInvalidImageContentException("Not enough data to read the logical screen descriptor");
         }
 
-        this.logicalScreenDescriptor = GifLogicalScreenDescriptor.Parse(this.buffer);
+        this.logicalScreenDescriptor = GifLogicalScreenDescriptor.Parse(this.buffer.Span);
     }
 
     /// <summary>
@@ -306,8 +306,8 @@ internal sealed class GifDecoderCore : IImageDecoderInternals
         long position = stream.Position;
         if (appLength == GifConstants.ApplicationBlockSize)
         {
-            stream.Read(this.buffer, 0, GifConstants.ApplicationBlockSize);
-            bool isXmp = this.buffer.AsSpan().StartsWith(GifConstants.XmpApplicationIdentificationBytes);
+            stream.Read(this.buffer.Span, 0, GifConstants.ApplicationBlockSize);
+            bool isXmp = this.buffer.Span.StartsWith(GifConstants.XmpApplicationIdentificationBytes);
             if (isXmp && !this.skipMetadata)
             {
                 GifXmpApplicationExtension extension = GifXmpApplicationExtension.Read(stream, this.memoryAllocator);
@@ -331,8 +331,8 @@ internal sealed class GifDecoderCore : IImageDecoderInternals
             // http://www.vurdalakov.net/misc/gif/netscape-buffering-application-extension
             if (subBlockSize == GifConstants.NetscapeLoopingSubBlockSize)
             {
-                stream.Read(this.buffer, 0, GifConstants.NetscapeLoopingSubBlockSize);
-                this.gifMetadata!.RepeatCount = GifNetscapeLoopingApplicationExtension.Parse(this.buffer.AsSpan(1)).RepeatCount;
+                stream.Read(this.buffer.Span, 0, GifConstants.NetscapeLoopingSubBlockSize);
+                this.gifMetadata!.RepeatCount = GifNetscapeLoopingApplicationExtension.Parse(this.buffer.Span.Slice(1)).RepeatCount;
                 stream.Skip(1); // Skip the terminator.
                 return;
             }
@@ -762,4 +762,12 @@ internal sealed class GifDecoderCore : IImageDecoderInternals
             }
         }
     }
+
+    private unsafe struct ScratchBuffer
+    {
+        private const int Size = 16;
+        private fixed byte scratch[Size];
+
+        public Span<byte> Span => MemoryMarshal.CreateSpan(ref this.scratch[0], Size);
+    }
 }

src/ImageSharp/Formats/Gif/GifEncoderCore.cs

@@ -28,11 +28,6 @@ internal sealed class GifEncoderCore : IImageEncoderInternals
     /// </summary>
     private readonly Configuration configuration;
 
-    /// <summary>
-    /// A reusable buffer used to reduce allocations.
-    /// </summary>
-    private readonly byte[] buffer = new byte[20];
-
     /// <summary>
     /// Whether to skip metadata during encode.
     /// </summary>
@@ -324,9 +319,10 @@ internal sealed class GifEncoderCore : IImageEncoderInternals
             backgroundColorIndex: unchecked((byte)transparencyIndex),
             ratio);
 
-        descriptor.WriteTo(this.buffer);
+        Span<byte> buffer = stackalloc byte[20];
+        descriptor.WriteTo(buffer);
 
-        stream.Write(this.buffer, 0, GifLogicalScreenDescriptor.Size);
+        stream.Write(buffer, 0, GifLogicalScreenDescriptor.Size);
     }
 
     /// <summary>
@@ -365,12 +361,14 @@ internal sealed class GifEncoderCore : IImageEncoderInternals
             return;
         }
 
+        Span<byte> buffer = stackalloc byte[2];
+
         for (int i = 0; i < metadata.Comments.Count; i++)
         {
             string comment = metadata.Comments[i];
-            this.buffer[0] = GifConstants.ExtensionIntroducer;
-            this.buffer[1] = GifConstants.CommentLabel;
-            stream.Write(this.buffer, 0, 2);
+            buffer[1] = GifConstants.CommentLabel;
+            buffer[0] = GifConstants.ExtensionIntroducer;
+            stream.Write(buffer);
 
             // Comment will be stored in chunks of 255 bytes, if it exceeds this size.
             ReadOnlySpan<char> commentSpan = comment.AsSpan();
@@ -437,22 +435,23 @@ internal sealed class GifEncoderCore : IImageEncoderInternals
     private void WriteExtension<TGifExtension>(TGifExtension extension, Stream stream)
         where TGifExtension : struct, IGifExtension
     {
-        IMemoryOwner<byte>? owner = null;
-        Span<byte> extensionBuffer;
         int extensionSize = extension.ContentLength;
 
         if (extensionSize == 0)
         {
             return;
         }
-        else if (extensionSize > this.buffer.Length - 3)
+
+        IMemoryOwner<byte>? owner = null;
+        Span<byte> extensionBuffer = stackalloc byte[0];    // workaround compiler limitation
+        if (extensionSize > 128)
         {
             owner = this.memoryAllocator.Allocate<byte>(extensionSize + 3);
             extensionBuffer = owner.GetSpan();
         }
         else
         {
-            extensionBuffer = this.buffer;
+            extensionBuffer = stackalloc byte[extensionSize + 3];
         }
 
         extensionBuffer[0] = GifConstants.ExtensionIntroducer;
@@ -489,9 +488,10 @@ internal sealed class GifEncoderCore : IImageEncoderInternals
             height: (ushort)image.Height,
             packed: packedValue);
 
-        descriptor.WriteTo(this.buffer);
+        Span<byte> buffer = stackalloc byte[20];
+        descriptor.WriteTo(buffer);
 
-        stream.Write(this.buffer, 0, GifImageDescriptor.Size);
+        stream.Write(buffer, 0, GifImageDescriptor.Size);
     }
 
     /// <summary>

src/ImageSharp/Formats/Jpeg/Components/Decoder/AdobeMarker.cs

@@ -62,7 +62,7 @@ internal readonly struct AdobeMarker : IEquatable<AdobeMarker>
     /// </summary>
     /// <param name="bytes">The byte array containing metadata to parse.</param>
     /// <param name="marker">The marker to return.</param>
-    public static bool TryParse(byte[] bytes, out AdobeMarker marker)
+    public static bool TryParse(ReadOnlySpan<byte> bytes, out AdobeMarker marker)
     {
         if (ProfileResolver.IsProfile(bytes, ProfileResolver.AdobeMarker))
         {

src/ImageSharp/Formats/Jpeg/Components/Decoder/ArithmeticScanDecoder.cs

@@ -53,6 +53,7 @@ internal class ArithmeticScanDecoder : IJpegScanDecoder
 
     private ArithmeticDecodingTable[] acDecodingTables;
 
+    // Don't make this a ReadOnlySpan<byte>, as the values need to get updated.
     private readonly byte[] fixedBin = { 113, 0, 0, 0 };
 
     private readonly CancellationToken cancellationToken;

src/ImageSharp/Formats/Jpeg/Components/Decoder/JFifMarker.cs

@@ -69,7 +69,7 @@ internal readonly struct JFifMarker : IEquatable<JFifMarker>
     /// </summary>
     /// <param name="bytes">The byte array containing metadata to parse.</param>
     /// <param name="marker">The marker to return.</param>
-    public static bool TryParse(byte[] bytes, out JFifMarker marker)
+    public static bool TryParse(ReadOnlySpan<byte> bytes, out JFifMarker marker)
     {
         if (ProfileResolver.IsProfile(bytes, ProfileResolver.JFifMarker))
         {

src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs

@@ -27,21 +27,6 @@ namespace SixLabors.ImageSharp.Formats.Jpeg;
 /// </summary>
 internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
 {
-    /// <summary>
-    /// The only supported precision
-    /// </summary>
-    private readonly byte[] supportedPrecisions = { 8, 12 };
-
-    /// <summary>
-    /// The buffer used to temporarily store bytes read from the stream.
-    /// </summary>
-    private readonly byte[] temp = new byte[2 * 16 * 4];
-
-    /// <summary>
-    /// The buffer used to read markers from the stream.
-    /// </summary>
-    private readonly byte[] markerBuffer = new byte[2];
-
     /// <summary>
     /// Whether the image has an EXIF marker.
     /// </summary>
@@ -139,6 +124,12 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
         this.skipMetadata = options.GeneralOptions.SkipMetadata;
     }
 
+    /// <summary>
+    /// Gets the only supported precisions
+    /// </summary>
+    // Refers to assembly's static data segment, no allocation occurs.
+    private static ReadOnlySpan<byte> SupportedPrecisions => new byte[] { 8, 12 };
+
     /// <inheritdoc />
     public DecoderOptions Options { get; }
 
@@ -257,24 +248,26 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
         using MemoryStream ms = new(tableBytes);
         using BufferedReadStream stream = new(this.configuration, ms);
 
+        Span<byte> markerBuffer = stackalloc byte[2];
+
         // Check for the Start Of Image marker.
-        int bytesRead = stream.Read(this.markerBuffer, 0, 2);
-        JpegFileMarker fileMarker = new(this.markerBuffer[1], 0);
+        int bytesRead = stream.Read(markerBuffer);
+        JpegFileMarker fileMarker = new(markerBuffer[1], 0);
         if (fileMarker.Marker != JpegConstants.Markers.SOI)
         {
             JpegThrowHelper.ThrowInvalidImageContentException("Missing SOI marker.");
         }
 
         // Read next marker.
-        bytesRead = stream.Read(this.markerBuffer, 0, 2);
-        fileMarker = new JpegFileMarker(this.markerBuffer[1], (int)stream.Position - 2);
+        bytesRead = stream.Read(markerBuffer);
+        fileMarker = new JpegFileMarker(markerBuffer[1], (int)stream.Position - 2);
 
         while (fileMarker.Marker != JpegConstants.Markers.EOI || (fileMarker.Marker == JpegConstants.Markers.EOI && fileMarker.Invalid))
         {
             if (!fileMarker.Invalid)
             {
                 // Get the marker length.
-                int markerContentByteSize = this.ReadUint16(stream) - 2;
+                int markerContentByteSize = ReadUint16(stream, markerBuffer) - 2;
 
                 // Check whether the stream actually has enough bytes to read
                 // markerContentByteSize is always positive so we cast
@@ -297,7 +290,7 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
                         this.ProcessDefineQuantizationTablesMarker(stream, markerContentByteSize);
                         break;
                     case JpegConstants.Markers.DRI:
-                        this.ProcessDefineRestartIntervalMarker(stream, markerContentByteSize);
+                        this.ProcessDefineRestartIntervalMarker(stream, markerContentByteSize, markerBuffer);
                         break;
                     case JpegConstants.Markers.EOI:
                         return;
@@ -305,13 +298,13 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
             }
 
             // Read next marker.
-            bytesRead = stream.Read(this.markerBuffer, 0, 2);
+            bytesRead = stream.Read(markerBuffer);
             if (bytesRead != 2)
             {
                 JpegThrowHelper.ThrowInvalidImageContentException("Not enough data to read marker");
             }
 
-            fileMarker = new JpegFileMarker(this.markerBuffer[1], 0);
+            fileMarker = new JpegFileMarker(markerBuffer[1], 0);
         }
     }
 
@@ -329,9 +322,11 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
 
         this.Metadata = new ImageMetadata();
 
+        Span<byte> markerBuffer = stackalloc byte[2];
+
         // Check for the Start Of Image marker.
-        stream.Read(this.markerBuffer, 0, 2);
-        JpegFileMarker fileMarker = new(this.markerBuffer[1], 0);
+        stream.Read(markerBuffer);
+        JpegFileMarker fileMarker = new(markerBuffer[1], 0);
         if (fileMarker.Marker != JpegConstants.Markers.SOI)
         {
             JpegThrowHelper.ThrowInvalidImageContentException("Missing SOI marker.");
@@ -349,7 +344,7 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
             if (!fileMarker.Invalid)
             {
                 // Get the marker length.
-                int markerContentByteSize = this.ReadUint16(stream) - 2;
+                int markerContentByteSize = ReadUint16(stream, markerBuffer) - 2;
 
                 // Check whether stream actually has enough bytes to read
                 // markerContentByteSize is always positive so we cast
@@ -446,7 +441,7 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
                         }
                         else
                         {
-                            this.ProcessDefineRestartIntervalMarker(stream, markerContentByteSize);
+                            this.ProcessDefineRestartIntervalMarker(stream, markerContentByteSize, markerBuffer);
                         }
 
                         break;
@@ -755,8 +750,10 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
             return;
         }
 
-        stream.Read(this.temp, 0, JFifMarker.Length);
-        if (!JFifMarker.TryParse(this.temp, out this.jFif))
+        Span<byte> temp = stackalloc byte[2 * 16 * 4];
+
+        stream.Read(temp, 0, JFifMarker.Length);
+        if (!JFifMarker.TryParse(temp, out this.jFif))
         {
             JpegThrowHelper.ThrowNotSupportedException("Unknown App0 Marker - Expected JFIF.");
         }
@@ -796,11 +793,13 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
             JpegThrowHelper.ThrowInvalidImageContentException("Bad App1 Marker length.");
         }
 
+        Span<byte> temp = stackalloc byte[2 * 16 * 4];
+
         // XMP marker is the longer then the EXIF marker, so first try read the EXIF marker bytes.
-        stream.Read(this.temp, 0, exifMarkerLength);
+        stream.Read(temp, 0, exifMarkerLength);
         remaining -= exifMarkerLength;
 
-        if (ProfileResolver.IsProfile(this.temp, ProfileResolver.ExifMarker))
+        if (ProfileResolver.IsProfile(temp, ProfileResolver.ExifMarker))
         {
             this.hasExif = true;
             byte[] profile = new byte[remaining];
@@ -819,7 +818,7 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
             remaining = 0;
         }
 
-        if (ProfileResolver.IsProfile(this.temp, ProfileResolver.XmpMarker[..exifMarkerLength]))
+        if (ProfileResolver.IsProfile(temp, ProfileResolver.XmpMarker[..exifMarkerLength]))
         {
             const int remainingXmpMarkerBytes = xmpMarkerLength - exifMarkerLength;
             if (remaining < remainingXmpMarkerBytes || this.skipMetadata)
@@ -829,9 +828,9 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
                 return;
             }
 
-            stream.Read(this.temp, exifMarkerLength, remainingXmpMarkerBytes);
+            stream.Read(temp, exifMarkerLength, remainingXmpMarkerBytes);
             remaining -= remainingXmpMarkerBytes;
-            if (ProfileResolver.IsProfile(this.temp, ProfileResolver.XmpMarker))
+            if (ProfileResolver.IsProfile(temp, ProfileResolver.XmpMarker))
             {
                 this.hasXmp = true;
                 byte[] profile = new byte[remaining];
@@ -870,8 +869,8 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
             return;
         }
 
-        byte[] identifier = new byte[icclength];
-        stream.Read(identifier, 0, icclength);
+        Span<byte> identifier = stackalloc byte[icclength];
+        stream.Read(identifier);
         remaining -= icclength; // We have read it by this point
 
         if (ProfileResolver.IsProfile(identifier, ProfileResolver.IccMarker))
@@ -911,13 +910,13 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
             return;
         }
 
-        stream.Read(this.temp, 0, ProfileResolver.AdobePhotoshopApp13Marker.Length);
+        Span<byte> temp = stackalloc byte[2 * 16 * 4];
+        stream.Read(temp, 0, ProfileResolver.AdobePhotoshopApp13Marker.Length);
         remaining -= ProfileResolver.AdobePhotoshopApp13Marker.Length;
-        if (ProfileResolver.IsProfile(this.temp, ProfileResolver.AdobePhotoshopApp13Marker))
+        if (ProfileResolver.IsProfile(temp, ProfileResolver.AdobePhotoshopApp13Marker))
         {
-            byte[] resourceBlockData = new byte[remaining];
-            stream.Read(resourceBlockData, 0, remaining);
-            Span<byte> blockDataSpan = resourceBlockData.AsSpan();
+            Span<byte> blockDataSpan = remaining <= 128 ? stackalloc byte[remaining] : new byte[remaining];
+            stream.Read(blockDataSpan);
 
             while (blockDataSpan.Length > 12)
             {
@@ -1047,10 +1046,12 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
             return;
         }
 
-        stream.Read(this.temp, 0, markerLength);
+        Span<byte> temp = stackalloc byte[2 * 16 * 4];
+
+        stream.Read(temp, 0, markerLength);
         remaining -= markerLength;
 
-        if (AdobeMarker.TryParse(this.temp, out this.adobe))
+        if (AdobeMarker.TryParse(temp, out this.adobe))
         {
             this.hasAdobeMarker = true;
         }
@@ -1072,6 +1073,7 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
     private void ProcessDefineQuantizationTablesMarker(BufferedReadStream stream, int remaining)
     {
         JpegMetadata jpegMetadata = this.Metadata.GetFormatMetadata(JpegFormat.Instance);
+        Span<byte> temp = stackalloc byte[2 * 16 * 4];
 
         while (remaining > 0)
         {
@@ -1102,13 +1104,13 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
                         JpegThrowHelper.ThrowBadMarker(nameof(JpegConstants.Markers.DQT), remaining);
                     }
 
-                    stream.Read(this.temp, 0, 64);
+                    stream.Read(temp, 0, 64);
                     remaining -= 64;
 
                     // Parsing quantization table & saving it in natural order
                     for (int j = 0; j < 64; j++)
                     {
-                        table[ZigZag.ZigZagOrder[j]] = this.temp[j];
+                        table[ZigZag.ZigZagOrder[j]] = temp[j];
                     }
 
                     break;
@@ -1121,13 +1123,13 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
                         JpegThrowHelper.ThrowBadMarker(nameof(JpegConstants.Markers.DQT), remaining);
                     }
 
-                    stream.Read(this.temp, 0, 128);
+                    stream.Read(temp, 0, 128);
                     remaining -= 128;
 
                     // Parsing quantization table & saving it in natural order
                     for (int j = 0; j < 64; j++)
                     {
-                        table[ZigZag.ZigZagOrder[j]] = (this.temp[2 * j] << 8) | this.temp[(2 * j) + 1];
+                        table[ZigZag.ZigZagOrder[j]] = (temp[2 * j] << 8) | temp[(2 * j) + 1];
                     }
 
                     break;
@@ -1174,28 +1176,30 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
             JpegThrowHelper.ThrowInvalidImageContentException("Multiple SOF markers. Only single frame jpegs supported.");
         }
 
+        Span<byte> temp = stackalloc byte[2 * 16 * 4];
+
         // Read initial marker definitions.
         const int length = 6;
-        int bytesRead = stream.Read(this.temp, 0, length);
+        int bytesRead = stream.Read(temp, 0, length);
         if (bytesRead != length)
         {
             JpegThrowHelper.ThrowInvalidImageContentException("SOF marker does not contain enough data.");
         }
 
         // 1 byte: Bits/sample precision.
-        byte precision = this.temp[0];
+        byte precision = temp[0];
 
         // Validate: only 8-bit and 12-bit precisions are supported.
-        if (Array.IndexOf(this.supportedPrecisions, precision) == -1)
+        if (SupportedPrecisions.IndexOf(precision) < 0)
         {
             JpegThrowHelper.ThrowInvalidImageContentException("Only 8-Bit and 12-Bit precision is supported.");
         }
 
         // 2 byte: Height
-        int frameHeight = (this.temp[1] << 8) | this.temp[2];
+        int frameHeight = (temp[1] << 8) | temp[2];
 
         // 2 byte: Width
-        int frameWidth = (this.temp[3] << 8) | this.temp[4];
+        int frameWidth = (temp[3] << 8) | temp[4];
 
         // Validate: width/height > 0 (they are upper-bounded by 2 byte max value so no need to check that).
         if (frameHeight == 0 || frameWidth == 0)
@@ -1204,7 +1208,7 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
         }
 
         // 1 byte: Number of components.
-        byte componentCount = this.temp[5];
+        byte componentCount = temp[5];
 
         // Validate: componentCount more than 4 can lead to a buffer overflow during stream
         // reading so we must limit it to 4.
@@ -1227,7 +1231,7 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
         }
 
         // components*3 bytes: component data
-        stream.Read(this.temp, 0, remaining);
+        stream.Read(temp, 0, remaining);
 
         // No need to pool this. They max out at 4
         this.Frame.ComponentIds = new byte[componentCount];
@@ -1240,10 +1244,10 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
         for (int i = 0; i < this.Frame.Components.Length; i++)
         {
             // 1 byte: component identifier
-            byte componentId = this.temp[index];
+            byte componentId = temp[index];
 
             // 1 byte: component sampling factors
-            byte hv = this.temp[index + 1];
+            byte hv = temp[index + 1];
             int h = (hv >> 4) & 15;
             int v = hv & 15;
 
@@ -1270,7 +1274,7 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
             }
 
             // 1 byte: quantization table destination selector
-            byte quantTableIndex = this.temp[index + 2];
+            byte quantTableIndex = temp[index + 2];
 
             // Validate: 0-3 range
             if (quantTableIndex > 3)
@@ -1379,7 +1383,8 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
     /// </summary>
     /// <param name="stream">The input stream.</param>
     /// <param name="remaining">The remaining bytes in the segment block.</param>
-    private void ProcessDefineRestartIntervalMarker(BufferedReadStream stream, int remaining)
+    /// <param name="markerBuffer">Scratch buffer.</param>
+    private void ProcessDefineRestartIntervalMarker(BufferedReadStream stream, int remaining, Span<byte> markerBuffer)
     {
         if (remaining != 2)
         {
@@ -1388,7 +1393,7 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
 
         // Save the reset interval, because it can come before or after the SOF marker.
         // If the reset interval comes after the SOF marker, the scanDecoder has not been created.
-        this.resetInterval = this.ReadUint16(stream);
+        this.resetInterval = ReadUint16(stream, markerBuffer);
 
         if (this.scanDecoder != null)
         {
@@ -1425,14 +1430,16 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
             JpegThrowHelper.ThrowBadMarker(nameof(JpegConstants.Markers.SOS), remaining);
         }
 
+        Span<byte> temp = stackalloc byte[2 * 16 * 4];
+
         // selectorsCount*2 bytes: component index + huffman tables indices
-        stream.Read(this.temp, 0, selectorsBytes);
+        stream.Read(temp, 0, selectorsBytes);
 
         this.Frame.Interleaved = this.Frame.ComponentCount == selectorsCount;
         for (int i = 0; i < selectorsBytes; i += 2)
         {
             // 1 byte: Component id
-            int componentSelectorId = this.temp[i];
+            int componentSelectorId = temp[i];
 
             int componentIndex = -1;
             for (int j = 0; j < this.Frame.ComponentIds.Length; j++)
@@ -1459,7 +1466,7 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
             // 1 byte: Huffman table selectors.
             // 4 bits - dc
             // 4 bits - ac
-            int tableSpec = this.temp[i + 1];
+            int tableSpec = temp[i + 1];
             int dcTableIndex = tableSpec >> 4;
             int acTableIndex = tableSpec & 15;
 
@@ -1475,17 +1482,17 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
         }
 
         // 3 bytes: Progressive scan decoding data.
-        int bytesRead = stream.Read(this.temp, 0, 3);
+        int bytesRead = stream.Read(temp, 0, 3);
         if (bytesRead != 3)
         {
             JpegThrowHelper.ThrowInvalidImageContentException("Not enough data to read progressive scan decoding data");
         }
 
-        this.scanDecoder.SpectralStart = this.temp[0];
+        this.scanDecoder.SpectralStart = temp[0];
 
-        this.scanDecoder.SpectralEnd = this.temp[1];
+        this.scanDecoder.SpectralEnd = temp[1];
 
-        int successiveApproximation = this.temp[2];
+        int successiveApproximation = temp[2];
         this.scanDecoder.SuccessiveHigh = successiveApproximation >> 4;
         this.scanDecoder.SuccessiveLow = successiveApproximation & 15;
 
@@ -1501,16 +1508,17 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
     /// Reads a <see cref="ushort"/> from the stream advancing it by two bytes.
     /// </summary>
     /// <param name="stream">The input stream.</param>
+    /// <param name="markerBuffer">The scratch buffer used for reading from the stream.</param>
     /// <returns>The <see cref="ushort"/></returns>
     [MethodImpl(InliningOptions.ShortMethod)]
-    private ushort ReadUint16(BufferedReadStream stream)
+    private static ushort ReadUint16(BufferedReadStream stream, Span<byte> markerBuffer)
     {
-        int bytesRead = stream.Read(this.markerBuffer, 0, 2);
+        int bytesRead = stream.Read(markerBuffer, 0, 2);
         if (bytesRead != 2)
         {
             JpegThrowHelper.ThrowInvalidImageContentException("jpeg stream does not contain enough data, could not read ushort.");
         }
 
-        return BinaryPrimitives.ReadUInt16BigEndian(this.markerBuffer);
+        return BinaryPrimitives.ReadUInt16BigEndian(markerBuffer);
     }
 }

src/ImageSharp/Formats/Jpeg/JpegEncoderCore.cs

@@ -25,11 +25,6 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
     /// </summary>
     private static readonly JpegFrameConfig[] FrameConfigs = CreateFrameConfigs();
 
-    /// <summary>
-    /// A scratch buffer to reduce allocations.
-    /// </summary>
-    private readonly byte[] buffer = new byte[20];
-
     private readonly JpegEncoder encoder;
 
     /// <summary>
@@ -67,6 +62,7 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
         cancellationToken.ThrowIfCancellationRequested();
 
         this.outputStream = stream;
+        Span<byte> buffer = stackalloc byte[20];
 
         ImageMetadata metadata = image.Metadata;
         JpegMetadata jpegMetadata = metadata.GetJpegMetadata();
@@ -76,39 +72,39 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
         using JpegFrame frame = new(image, frameConfig, interleaved);
 
         // Write the Start Of Image marker.
-        this.WriteStartOfImage();
+        this.WriteStartOfImage(buffer);
 
         // Write APP0 marker
         if (frameConfig.AdobeColorTransformMarkerFlag is null)
         {
-            this.WriteJfifApplicationHeader(metadata);
+            this.WriteJfifApplicationHeader(metadata, buffer);
         }
 
         // Write APP14 marker with adobe color extension
         else
         {
-            this.WriteApp14Marker(frameConfig.AdobeColorTransformMarkerFlag.Value);
+            this.WriteApp14Marker(frameConfig.AdobeColorTransformMarkerFlag.Value, buffer);
         }
 
         // Write Exif, XMP, ICC and IPTC profiles
-        this.WriteProfiles(metadata);
+        this.WriteProfiles(metadata, buffer);
 
         // Write the image dimensions.
-        this.WriteStartOfFrame(image.Width, image.Height, frameConfig);
+        this.WriteStartOfFrame(image.Width, image.Height, frameConfig, buffer);
 
         // Write the Huffman tables.
         HuffmanScanEncoder scanEncoder = new(frame.BlocksPerMcu, stream);
-        this.WriteDefineHuffmanTables(frameConfig.HuffmanTables, scanEncoder);
+        this.WriteDefineHuffmanTables(frameConfig.HuffmanTables, scanEncoder, buffer);
 
         // Write the quantization tables.
-        this.WriteDefineQuantizationTables(frameConfig.QuantizationTables, this.encoder.Quality, jpegMetadata);
+        this.WriteDefineQuantizationTables(frameConfig.QuantizationTables, this.encoder.Quality, jpegMetadata, buffer);
 
         // Write scans with actual pixel data
         using SpectralConverter<TPixel> spectralConverter = new(frame, image, this.QuantizationTables);
-        this.WriteHuffmanScans(frame, frameConfig, spectralConverter, scanEncoder, cancellationToken);
+        this.WriteHuffmanScans(frame, frameConfig, spectralConverter, scanEncoder, buffer, cancellationToken);
 
         // Write the End Of Image marker.
-        this.WriteEndOfImageMarker();
+        this.WriteEndOfImageMarker(buffer);
 
         stream.Flush();
     }
@@ -116,58 +112,59 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
     /// <summary>
     /// Write the start of image marker.
     /// </summary>
-    private void WriteStartOfImage()
+    private void WriteStartOfImage(Span<byte> buffer)
     {
         // Markers are always prefixed with 0xff.
-        this.buffer[0] = JpegConstants.Markers.XFF;
-        this.buffer[1] = JpegConstants.Markers.SOI;
+        buffer[1] = JpegConstants.Markers.SOI;
+        buffer[0] = JpegConstants.Markers.XFF;
 
-        this.outputStream.Write(this.buffer, 0, 2);
+        this.outputStream.Write(buffer, 0, 2);
     }
 
     /// <summary>
     /// Writes the application header containing the JFIF identifier plus extra data.
     /// </summary>
     /// <param name="meta">The image metadata.</param>
-    private void WriteJfifApplicationHeader(ImageMetadata meta)
+    /// <param name="buffer">Temporary buffer.</param>
+    private void WriteJfifApplicationHeader(ImageMetadata meta, Span<byte> buffer)
     {
-        // Write the JFIF headers
-        this.buffer[0] = JpegConstants.Markers.XFF;
-        this.buffer[1] = JpegConstants.Markers.APP0; // Application Marker
-        this.buffer[2] = 0x00;
-        this.buffer[3] = 0x10;
-        this.buffer[4] = 0x4a; // J
-        this.buffer[5] = 0x46; // F
-        this.buffer[6] = 0x49; // I
-        this.buffer[7] = 0x46; // F
-        this.buffer[8] = 0x00; // = "JFIF",'\0'
-        this.buffer[9] = 0x01; // versionhi
-        this.buffer[10] = 0x01; // versionlo
+        // Write the JFIF headers (highest index first to avoid additional bound checks)
+        buffer[10] = 0x01; // versionlo
+        buffer[0] = JpegConstants.Markers.XFF;
+        buffer[1] = JpegConstants.Markers.APP0; // Application Marker
+        buffer[2] = 0x00;
+        buffer[3] = 0x10;
+        buffer[4] = 0x4a; // J
+        buffer[5] = 0x46; // F
+        buffer[6] = 0x49; // I
+        buffer[7] = 0x46; // F
+        buffer[8] = 0x00; // = "JFIF",'\0'
+        buffer[9] = 0x01; // versionhi
 
         // Resolution. Big Endian
-        Span<byte> hResolution = this.buffer.AsSpan(12, 2);
-        Span<byte> vResolution = this.buffer.AsSpan(14, 2);
+        Span<byte> hResolution = buffer.Slice(12, 2);
+        Span<byte> vResolution = buffer.Slice(14, 2);
 
         if (meta.ResolutionUnits == PixelResolutionUnit.PixelsPerMeter)
         {
             // Scale down to PPI
-            this.buffer[11] = (byte)PixelResolutionUnit.PixelsPerInch; // xyunits
+            buffer[11] = (byte)PixelResolutionUnit.PixelsPerInch; // xyunits
             BinaryPrimitives.WriteInt16BigEndian(hResolution, (short)Math.Round(UnitConverter.MeterToInch(meta.HorizontalResolution)));
             BinaryPrimitives.WriteInt16BigEndian(vResolution, (short)Math.Round(UnitConverter.MeterToInch(meta.VerticalResolution)));
         }
         else
         {
             // We can simply pass the value.
-            this.buffer[11] = (byte)meta.ResolutionUnits; // xyunits
+            buffer[11] = (byte)meta.ResolutionUnits; // xyunits
             BinaryPrimitives.WriteInt16BigEndian(hResolution, (short)Math.Round(meta.HorizontalResolution));
             BinaryPrimitives.WriteInt16BigEndian(vResolution, (short)Math.Round(meta.VerticalResolution));
         }
 
         // No thumbnail
-        this.buffer[16] = 0x00; // Thumbnail width
-        this.buffer[17] = 0x00; // Thumbnail height
+        buffer[17] = 0x00; // Thumbnail height
+        buffer[16] = 0x00; // Thumbnail width
 
-        this.outputStream.Write(this.buffer, 0, 18);
+        this.outputStream.Write(buffer, 0, 18);
     }
 
     /// <summary>
@@ -175,8 +172,9 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
     /// </summary>
     /// <param name="tableConfigs">The table configuration.</param>
     /// <param name="scanEncoder">The scan encoder.</param>
+    /// <param name="buffer">Temporary buffer.</param>
     /// <exception cref="ArgumentNullException"><paramref name="tableConfigs"/> is <see langword="null"/>.</exception>
-    private void WriteDefineHuffmanTables(JpegHuffmanTableConfig[] tableConfigs, HuffmanScanEncoder scanEncoder)
+    private void WriteDefineHuffmanTables(JpegHuffmanTableConfig[] tableConfigs, HuffmanScanEncoder scanEncoder, Span<byte> buffer)
     {
         if (tableConfigs is null)
         {
@@ -190,7 +188,7 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
             markerlen += 1 + 16 + tableConfigs[i].Table.Values.Length;
         }
 
-        this.WriteMarkerHeader(JpegConstants.Markers.DHT, markerlen);
+        this.WriteMarkerHeader(JpegConstants.Markers.DHT, markerlen, buffer);
         for (int i = 0; i < tableConfigs.Length; i++)
         {
             JpegHuffmanTableConfig tableConfig = tableConfigs[i];
@@ -208,37 +206,39 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
     /// Writes the APP14 marker to indicate the image is in RGB color space.
     /// </summary>
     /// <param name="colorTransform">The color transform byte.</param>
-    private void WriteApp14Marker(byte colorTransform)
+    /// <param name="buffer">Temporary buffer.</param>
+    private void WriteApp14Marker(byte colorTransform, Span<byte> buffer)
     {
-        this.WriteMarkerHeader(JpegConstants.Markers.APP14, 2 + Components.Decoder.AdobeMarker.Length);
+        this.WriteMarkerHeader(JpegConstants.Markers.APP14, 2 + Components.Decoder.AdobeMarker.Length, buffer);
 
-        // Identifier: ASCII "Adobe".
-        this.buffer[0] = 0x41;
-        this.buffer[1] = 0x64;
-        this.buffer[2] = 0x6F;
-        this.buffer[3] = 0x62;
-        this.buffer[4] = 0x65;
+        // Identifier: ASCII "Adobe" (highest index first to avoid additional bound checks).
+        buffer[4] = 0x65;
+        buffer[0] = 0x41;
+        buffer[1] = 0x64;
+        buffer[2] = 0x6F;
+        buffer[3] = 0x62;
 
         // Version, currently 100.
-        BinaryPrimitives.WriteInt16BigEndian(this.buffer.AsSpan(5, 2), 100);
+        BinaryPrimitives.WriteInt16BigEndian(buffer.Slice(5, 2), 100);
 
         // Flags0
-        BinaryPrimitives.WriteInt16BigEndian(this.buffer.AsSpan(7, 2), 0);
+        BinaryPrimitives.WriteInt16BigEndian(buffer.Slice(7, 2), 0);
 
         // Flags1
-        BinaryPrimitives.WriteInt16BigEndian(this.buffer.AsSpan(9, 2), 0);
+        BinaryPrimitives.WriteInt16BigEndian(buffer.Slice(9, 2), 0);
 
         // Color transform byte
-        this.buffer[11] = colorTransform;
+        buffer[11] = colorTransform;
 
-        this.outputStream.Write(this.buffer.AsSpan(0, 12));
+        this.outputStream.Write(buffer.Slice(0, 12));
     }
 
     /// <summary>
     /// Writes the EXIF profile.
     /// </summary>
     /// <param name="exifProfile">The exif profile.</param>
-    private void WriteExifProfile(ExifProfile exifProfile)
+    /// <param name="buffer">Temporary buffer.</param>
+    private void WriteExifProfile(ExifProfile exifProfile, Span<byte> buffer)
     {
         if (exifProfile is null || exifProfile.Values.Count == 0)
         {
@@ -262,7 +262,7 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
         int app1Length = bytesToWrite + 2;
 
         // Write the app marker, EXIF marker, and data
-        this.WriteApp1Header(app1Length);
+        this.WriteApp1Header(app1Length, buffer);
         this.outputStream.Write(Components.Decoder.ProfileResolver.ExifMarker);
         this.outputStream.Write(data, 0, bytesToWrite - exifMarkerLength);
         remaining -= bytesToWrite;
@@ -273,7 +273,7 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
             bytesToWrite = remaining > maxBytesWithExifId ? maxBytesWithExifId : remaining;
             app1Length = bytesToWrite + 2 + exifMarkerLength;
 
-            this.WriteApp1Header(app1Length);
+            this.WriteApp1Header(app1Length, buffer);
 
             // Write Exif00 marker
             this.outputStream.Write(Components.Decoder.ProfileResolver.ExifMarker);
@@ -289,10 +289,11 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
     /// Writes the IPTC metadata.
     /// </summary>
     /// <param name="iptcProfile">The iptc metadata to write.</param>
+    /// <param name="buffer">Temporary buffer.</param>
     /// <exception cref="ImageFormatException">
     /// Thrown if the IPTC profile size exceeds the limit of 65533 bytes.
     /// </exception>
-    private void WriteIptcProfile(IptcProfile iptcProfile)
+    private void WriteIptcProfile(IptcProfile iptcProfile, Span<byte> buffer)
     {
         const int maxBytes = 65533;
         if (iptcProfile is null || !iptcProfile.Values.Any())
@@ -316,14 +317,14 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
                           Components.Decoder.ProfileResolver.AdobeImageResourceBlockMarker.Length +
                           Components.Decoder.ProfileResolver.AdobeIptcMarker.Length +
                           2 + 4 + data.Length;
-        this.WriteAppHeader(app13Length, JpegConstants.Markers.APP13);
+        this.WriteAppHeader(app13Length, JpegConstants.Markers.APP13, buffer);
         this.outputStream.Write(Components.Decoder.ProfileResolver.AdobePhotoshopApp13Marker);
         this.outputStream.Write(Components.Decoder.ProfileResolver.AdobeImageResourceBlockMarker);
         this.outputStream.Write(Components.Decoder.ProfileResolver.AdobeIptcMarker);
         this.outputStream.WriteByte(0); // a empty pascal string (padded to make size even)
         this.outputStream.WriteByte(0);
-        BinaryPrimitives.WriteInt32BigEndian(this.buffer, data.Length);
-        this.outputStream.Write(this.buffer, 0, 4);
+        BinaryPrimitives.WriteInt32BigEndian(buffer, data.Length);
+        this.outputStream.Write(buffer, 0, 4);
         this.outputStream.Write(data, 0, data.Length);
     }
 
@@ -331,10 +332,11 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
     /// Writes the XMP metadata.
     /// </summary>
     /// <param name="xmpProfile">The XMP metadata to write.</param>
+    /// <param name="buffer">Temporary buffer.</param>
     /// <exception cref="ImageFormatException">
     /// Thrown if the XMP profile size exceeds the limit of 65533 bytes.
     /// </exception>
-    private void WriteXmpProfile(XmpProfile xmpProfile)
+    private void WriteXmpProfile(XmpProfile xmpProfile, Span<byte> buffer)
     {
         if (xmpProfile is null)
         {
@@ -367,7 +369,7 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
             dataLength -= length;
 
             int app1Length = 2 + Components.Decoder.ProfileResolver.XmpMarker.Length + length;
-            this.WriteApp1Header(app1Length);
+            this.WriteApp1Header(app1Length, buffer);
             this.outputStream.Write(Components.Decoder.ProfileResolver.XmpMarker);
             this.outputStream.Write(data, offset, length);
 
@@ -379,32 +381,35 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
     /// Writes the App1 header.
     /// </summary>
     /// <param name="app1Length">The length of the data the app1 marker contains.</param>
-    private void WriteApp1Header(int app1Length)
-        => this.WriteAppHeader(app1Length, JpegConstants.Markers.APP1);
+    /// <param name="buffer">Temporary buffer.</param>
+    private void WriteApp1Header(int app1Length, Span<byte> buffer)
+        => this.WriteAppHeader(app1Length, JpegConstants.Markers.APP1, buffer);
 
     /// <summary>
     /// Writes a AppX header.
     /// </summary>
     /// <param name="length">The length of the data the app marker contains.</param>
     /// <param name="appMarker">The app marker to write.</param>
-    private void WriteAppHeader(int length, byte appMarker)
+    /// <param name="buffer">Temporary buffer.</param>
+    private void WriteAppHeader(int length, byte appMarker, Span<byte> buffer)
     {
-        this.buffer[0] = JpegConstants.Markers.XFF;
-        this.buffer[1] = appMarker;
-        this.buffer[2] = (byte)((length >> 8) & 0xFF);
-        this.buffer[3] = (byte)(length & 0xFF);
+        buffer[0] = JpegConstants.Markers.XFF;
+        buffer[1] = appMarker;
+        buffer[2] = (byte)((length >> 8) & 0xFF);
+        buffer[3] = (byte)(length & 0xFF);
 
-        this.outputStream.Write(this.buffer, 0, 4);
+        this.outputStream.Write(buffer, 0, 4);
     }
 
     /// <summary>
     /// Writes the ICC profile.
     /// </summary>
     /// <param name="iccProfile">The ICC profile to write.</param>
+    /// <param name="buffer">Temporary buffer.</param>
     /// <exception cref="ImageFormatException">
     /// Thrown if any of the ICC profiles size exceeds the limit.
     /// </exception>
-    private void WriteIccProfile(IccProfile iccProfile)
+    private void WriteIccProfile(IccProfile iccProfile, Span<byte> buffer)
     {
         if (iccProfile is null)
         {
@@ -446,30 +451,31 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
 
             dataLength -= length;
 
-            this.buffer[0] = JpegConstants.Markers.XFF;
-            this.buffer[1] = JpegConstants.Markers.APP2; // Application Marker
+            buffer[0] = JpegConstants.Markers.XFF;
+            buffer[1] = JpegConstants.Markers.APP2; // Application Marker
             int markerLength = length + 16;
-            this.buffer[2] = (byte)((markerLength >> 8) & 0xFF);
-            this.buffer[3] = (byte)(markerLength & 0xFF);
-
-            this.outputStream.Write(this.buffer, 0, 4);
-
-            this.buffer[0] = (byte)'I';
-            this.buffer[1] = (byte)'C';
-            this.buffer[2] = (byte)'C';
-            this.buffer[3] = (byte)'_';
-            this.buffer[4] = (byte)'P';
-            this.buffer[5] = (byte)'R';
-            this.buffer[6] = (byte)'O';
-            this.buffer[7] = (byte)'F';
-            this.buffer[8] = (byte)'I';
-            this.buffer[9] = (byte)'L';
-            this.buffer[10] = (byte)'E';
-            this.buffer[11] = 0x00;
-            this.buffer[12] = (byte)current; // The position within the collection.
-            this.buffer[13] = (byte)count; // The total number of profiles.
-
-            this.outputStream.Write(this.buffer, 0, iccOverheadLength);
+            buffer[2] = (byte)((markerLength >> 8) & 0xFF);
+            buffer[3] = (byte)(markerLength & 0xFF);
+
+            this.outputStream.Write(buffer, 0, 4);
+
+            // We write the highest index first, to have only one bound check.
+            buffer[13] = (byte)count; // The total number of profiles.
+            buffer[12] = (byte)current; // The position within the collection.
+            buffer[11] = 0x00;
+            buffer[0] = (byte)'I';
+            buffer[1] = (byte)'C';
+            buffer[2] = (byte)'C';
+            buffer[3] = (byte)'_';
+            buffer[4] = (byte)'P';
+            buffer[5] = (byte)'R';
+            buffer[6] = (byte)'O';
+            buffer[7] = (byte)'F';
+            buffer[8] = (byte)'I';
+            buffer[9] = (byte)'L';
+            buffer[10] = (byte)'E';
+
+            this.outputStream.Write(buffer, 0, iccOverheadLength);
             this.outputStream.Write(data, offset, length);
 
             current++;
@@ -481,7 +487,8 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
     /// Writes the metadata profiles to the image.
     /// </summary>
     /// <param name="metadata">The image metadata.</param>
-    private void WriteProfiles(ImageMetadata metadata)
+    /// <param name="buffer">Temporary buffer.</param>
+    private void WriteProfiles(ImageMetadata metadata, Span<byte> buffer)
     {
         if (metadata is null)
         {
@@ -494,10 +501,10 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
         // - APP2 ICC
         // - APP13 IPTC
         metadata.SyncProfiles();
-        this.WriteExifProfile(metadata.ExifProfile);
-        this.WriteXmpProfile(metadata.XmpProfile);
-        this.WriteIccProfile(metadata.IccProfile);
-        this.WriteIptcProfile(metadata.IptcProfile);
+        this.WriteExifProfile(metadata.ExifProfile, buffer);
+        this.WriteXmpProfile(metadata.XmpProfile, buffer);
+        this.WriteIccProfile(metadata.IccProfile, buffer);
+        this.WriteIptcProfile(metadata.IptcProfile, buffer);
     }
 
     /// <summary>
@@ -506,25 +513,26 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
     /// <param name="width">The frame width.</param>
     /// <param name="height">The frame height.</param>
     /// <param name="frame">The frame configuration.</param>
-    private void WriteStartOfFrame(int width, int height, JpegFrameConfig frame)
+    /// <param name="buffer">Temporary buffer.</param>
+    private void WriteStartOfFrame(int width, int height, JpegFrameConfig frame, Span<byte> buffer)
     {
         JpegComponentConfig[] components = frame.Components;
 
         // Length (high byte, low byte), 8 + components * 3.
         int markerlen = 8 + (3 * components.Length);
-        this.WriteMarkerHeader(JpegConstants.Markers.SOF0, markerlen);
-        this.buffer[0] = 8; // Data Precision. 8 for now, 12 and 16 bit jpegs not supported
-        this.buffer[1] = (byte)(height >> 8);
-        this.buffer[2] = (byte)(height & 0xff); // (2 bytes, Hi-Lo), must be > 0 if DNL not supported
-        this.buffer[3] = (byte)(width >> 8);
-        this.buffer[4] = (byte)(width & 0xff); // (2 bytes, Hi-Lo), must be > 0 if DNL not supported
-        this.buffer[5] = (byte)components.Length;
+        this.WriteMarkerHeader(JpegConstants.Markers.SOF0, markerlen, buffer);
+        buffer[5] = (byte)components.Length;
+        buffer[0] = 8; // Data Precision. 8 for now, 12 and 16 bit jpegs not supported
+        buffer[1] = (byte)(height >> 8);
+        buffer[2] = (byte)(height & 0xff); // (2 bytes, Hi-Lo), must be > 0 if DNL not supported
+        buffer[3] = (byte)(width >> 8);
+        buffer[4] = (byte)(width & 0xff); // (2 bytes, Hi-Lo), must be > 0 if DNL not supported
 
         // Components data
         for (int i = 0; i < components.Length; i++)
         {
             int i3 = 3 * i;
-            Span<byte> bufferSpan = this.buffer.AsSpan(i3 + 6, 3);
+            Span<byte> bufferSpan = buffer.Slice(i3 + 6, 3);
 
             // Quantization table selector
             bufferSpan[2] = (byte)components[i].QuantizatioTableIndex;
@@ -538,14 +546,15 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
             bufferSpan[0] = components[i].Id;
         }
 
-        this.outputStream.Write(this.buffer, 0, (3 * (components.Length - 1)) + 9);
+        this.outputStream.Write(buffer, 0, (3 * (components.Length - 1)) + 9);
     }
 
     /// <summary>
     /// Writes the StartOfScan marker.
     /// </summary>
     /// <param name="components">The collecction of component configuration items.</param>
-    private void WriteStartOfScan(Span<JpegComponentConfig> components)
+    /// <param name="buffer">Temporary buffer.</param>
+    private void WriteStartOfScan(Span<JpegComponentConfig> components, Span<byte> buffer)
     {
         // Write the SOS (Start Of Scan) marker "\xff\xda" followed by 12 bytes:
         // - the marker length "\x00\x0c",
@@ -556,14 +565,14 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
         // - the bytes "\x00\x3f\x00". Section B.2.3 of the spec says that for
         // sequential DCTs, those bytes (8-bit Ss, 8-bit Se, 4-bit Ah, 4-bit Al)
         // should be 0x00, 0x3f, 0x00&lt;&lt;4 | 0x00.
-        this.buffer[0] = JpegConstants.Markers.XFF;
-        this.buffer[1] = JpegConstants.Markers.SOS;
+        buffer[1] = JpegConstants.Markers.SOS;
+        buffer[0] = JpegConstants.Markers.XFF;
 
         // Length (high byte, low byte), must be 6 + 2 * (number of components in scan)
         int sosSize = 6 + (2 * components.Length);
-        this.buffer[2] = 0x00;
-        this.buffer[3] = (byte)sosSize;
-        this.buffer[4] = (byte)components.Length; // Number of components in a scan
+        buffer[4] = (byte)components.Length; // Number of components in a scan
+        buffer[3] = (byte)sosSize;
+        buffer[2] = 0x00;
 
         // Components data
         for (int i = 0; i < components.Length; i++)
@@ -571,27 +580,28 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
             int i2 = 2 * i;
 
             // Id
-            this.buffer[i2 + 5] = components[i].Id;
+            buffer[i2 + 5] = components[i].Id;
 
             // Table selectors
             int tableSelectors = (components[i].DcTableSelector << 4) | components[i].AcTableSelector;
-            this.buffer[i2 + 6] = (byte)tableSelectors;
+            buffer[i2 + 6] = (byte)tableSelectors;
         }
 
-        this.buffer[sosSize - 1] = 0x00; // Ss - Start of spectral selection.
-        this.buffer[sosSize] = 0x3f; // Se - End of spectral selection.
-        this.buffer[sosSize + 1] = 0x00; // Ah + Ah (Successive approximation bit position high + low)
-        this.outputStream.Write(this.buffer, 0, sosSize + 2);
+        buffer[sosSize - 1] = 0x00; // Ss - Start of spectral selection.
+        buffer[sosSize] = 0x3f; // Se - End of spectral selection.
+        buffer[sosSize + 1] = 0x00; // Ah + Ah (Successive approximation bit position high + low)
+        this.outputStream.Write(buffer, 0, sosSize + 2);
     }
 
     /// <summary>
     /// Writes the EndOfImage marker.
     /// </summary>
-    private void WriteEndOfImageMarker()
+    /// <param name="buffer">Temporary buffer.</param>
+    private void WriteEndOfImageMarker(Span<byte> buffer)
     {
-        this.buffer[0] = JpegConstants.Markers.XFF;
-        this.buffer[1] = JpegConstants.Markers.EOI;
-        this.outputStream.Write(this.buffer, 0, 2);
+        buffer[1] = JpegConstants.Markers.EOI;
+        buffer[0] = JpegConstants.Markers.XFF;
+        this.outputStream.Write(buffer, 0, 2);
     }
 
     /// <summary>
@@ -602,12 +612,14 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
     /// <param name="frameConfig">The frame configuration.</param>
     /// <param name="spectralConverter">The spectral converter.</param>
     /// <param name="encoder">The scan encoder.</param>
+    /// <param name="buffer">Temporary buffer.</param>
     /// <param name="cancellationToken">The cancellation token.</param>
     private void WriteHuffmanScans<TPixel>(
         JpegFrame frame,
         JpegFrameConfig frameConfig,
         SpectralConverter<TPixel> spectralConverter,
         HuffmanScanEncoder encoder,
+        Span<byte> buffer,
         CancellationToken cancellationToken)
         where TPixel : unmanaged, IPixel<TPixel>
     {
@@ -615,14 +627,14 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
         {
             frame.AllocateComponents(fullScan: false);
 
-            this.WriteStartOfScan(frameConfig.Components);
+            this.WriteStartOfScan(frameConfig.Components, buffer);
             encoder.EncodeScanBaselineSingleComponent(frame.Components[0], spectralConverter, cancellationToken);
         }
         else if (frame.Interleaved)
         {
             frame.AllocateComponents(fullScan: false);
 
-            this.WriteStartOfScan(frameConfig.Components);
+            this.WriteStartOfScan(frameConfig.Components, buffer);
             encoder.EncodeScanBaselineInterleaved(frameConfig.EncodingColor, frame, spectralConverter, cancellationToken);
         }
         else
@@ -633,7 +645,7 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
             Span<JpegComponentConfig> components = frameConfig.Components;
             for (int i = 0; i < frame.Components.Length; i++)
             {
-                this.WriteStartOfScan(components.Slice(i, 1));
+                this.WriteStartOfScan(components.Slice(i, 1), buffer);
                 encoder.EncodeScanBaseline(frame.Components[i], cancellationToken);
             }
         }
@@ -644,14 +656,16 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
     /// </summary>
     /// <param name="marker">The marker to write.</param>
     /// <param name="length">The marker length.</param>
-    private void WriteMarkerHeader(byte marker, int length)
+    /// <param name="buffer">Temporary buffer.</param>
+    private void WriteMarkerHeader(byte marker, int length, Span<byte> buffer)
     {
         // Markers are always prefixed with 0xff.
-        this.buffer[0] = JpegConstants.Markers.XFF;
-        this.buffer[1] = marker;
-        this.buffer[2] = (byte)(length >> 8);
-        this.buffer[3] = (byte)(length & 0xff);
-        this.outputStream.Write(this.buffer, 0, 4);
+        buffer[3] = (byte)(length & 0xff);
+        buffer[2] = (byte)(length >> 8);
+        buffer[1] = marker;
+        buffer[0] = JpegConstants.Markers.XFF;
+
+        this.outputStream.Write(buffer, 0, 4);
     }
 
     /// <summary>
@@ -668,15 +682,16 @@ internal sealed unsafe partial class JpegEncoderCore : IImageEncoderInternals
     /// <param name="configs">Quantization tables configs.</param>
     /// <param name="optionsQuality">Optional quality value from the options.</param>
     /// <param name="metadata">Jpeg metadata instance.</param>
-    private void WriteDefineQuantizationTables(JpegQuantizationTableConfig[] configs, int? optionsQuality, JpegMetadata metadata)
+    /// <param name="tmpBuffer">Temporary buffer.</param>
+    private void WriteDefineQuantizationTables(JpegQuantizationTableConfig[] configs, int? optionsQuality, JpegMetadata metadata, Span<byte> tmpBuffer)
     {
         int dataLen = configs.Length * (1 + Block8x8.Size);
 
         // Marker + quantization table lengths.
         int markerlen = 2 + dataLen;
-        this.WriteMarkerHeader(JpegConstants.Markers.DQT, markerlen);
+        this.WriteMarkerHeader(JpegConstants.Markers.DQT, markerlen, tmpBuffer);
 
-        byte[] buffer = new byte[dataLen];
+        Span<byte> buffer = dataLen <= 256 ? stackalloc byte[dataLen] : new byte[dataLen];
         int offset = 0;
 
         Block8x8F workspaceBlock = default;

src/ImageSharp/Formats/Png/PngDecoderCore.cs

@@ -28,11 +28,6 @@ namespace SixLabors.ImageSharp.Formats.Png;
 /// </summary>
 internal sealed class PngDecoderCore : IImageDecoderInternals
 {
-    /// <summary>
-    /// Reusable buffer.
-    /// </summary>
-    private readonly byte[] buffer = new byte[4];
-
     /// <summary>
     /// The general decoder options.
     /// </summary>
@@ -154,9 +149,11 @@ internal sealed class PngDecoderCore : IImageDecoderInternals
         this.currentStream = stream;
         this.currentStream.Skip(8);
         Image<TPixel> image = null;
+        Span<byte> buffer = stackalloc byte[20];
+
         try
         {
-            while (this.TryReadChunk(out PngChunk chunk))
+            while (this.TryReadChunk(buffer, out PngChunk chunk))
             {
                 try
                 {
@@ -252,10 +249,13 @@ internal sealed class PngDecoderCore : IImageDecoderInternals
         ImageMetadata metadata = new();
         PngMetadata pngMetadata = metadata.GetPngMetadata();
         this.currentStream = stream;
+        Span<byte> buffer = stackalloc byte[20];
+
         this.currentStream.Skip(8);
+
         try
         {
-            while (this.TryReadChunk(out PngChunk chunk))
+            while (this.TryReadChunk(buffer, out PngChunk chunk))
             {
                 try
                 {
@@ -1401,9 +1401,11 @@ internal sealed class PngDecoderCore : IImageDecoderInternals
             return 0;
         }
 
-        this.currentStream.Read(this.buffer, 0, 4);
+        Span<byte> buffer = stackalloc byte[20];
+
+        this.currentStream.Read(buffer, 0, 4);
 
-        if (this.TryReadChunk(out PngChunk chunk))
+        if (this.TryReadChunk(buffer, out PngChunk chunk))
         {
             if (chunk.Type == PngChunkType.Data)
             {
@@ -1420,11 +1422,12 @@ internal sealed class PngDecoderCore : IImageDecoderInternals
     /// <summary>
     /// Reads a chunk from the stream.
     /// </summary>
+    /// <param name="buffer">Temporary buffer.</param>
     /// <param name="chunk">The image format chunk.</param>
     /// <returns>
     /// The <see cref="PngChunk"/>.
     /// </returns>
-    private bool TryReadChunk(out PngChunk chunk)
+    private bool TryReadChunk(Span<byte> buffer, out PngChunk chunk)
     {
         if (this.nextChunk != null)
         {
@@ -1435,7 +1438,7 @@ internal sealed class PngDecoderCore : IImageDecoderInternals
             return true;
         }
 
-        if (!this.TryReadChunkLength(out int length))
+        if (!this.TryReadChunkLength(buffer, out int length))
         {
             chunk = default;
 
@@ -1446,7 +1449,7 @@ internal sealed class PngDecoderCore : IImageDecoderInternals
         while (length < 0 || length > (this.currentStream.Length - this.currentStream.Position))
         {
             // Not a valid chunk so try again until we reach a known chunk.
-            if (!this.TryReadChunkLength(out length))
+            if (!this.TryReadChunkLength(buffer, out length))
             {
                 chunk = default;
 
@@ -1454,7 +1457,7 @@ internal sealed class PngDecoderCore : IImageDecoderInternals
             }
         }
 
-        PngChunkType type = this.ReadChunkType();
+        PngChunkType type = this.ReadChunkType(buffer);
 
         // If we're reading color metadata only we're only interested in the IHDR and tRNS chunks.
         // We can skip all other chunk data in the stream for better performance.
@@ -1471,7 +1474,7 @@ internal sealed class PngDecoderCore : IImageDecoderInternals
             type: type,
             data: this.ReadChunkData(length));
 
-        this.ValidateChunk(chunk);
+        this.ValidateChunk(chunk, buffer);
 
         // Restore the stream position for IDAT chunks, because it will be decoded later and
         // was only read to verifying the CRC is correct.
@@ -1487,9 +1490,10 @@ internal sealed class PngDecoderCore : IImageDecoderInternals
     /// Validates the png chunk.
     /// </summary>
     /// <param name="chunk">The <see cref="PngChunk"/>.</param>
-    private void ValidateChunk(in PngChunk chunk)
+    /// <param name="buffer">Temporary buffer.</param>
+    private void ValidateChunk(in PngChunk chunk, Span<byte> buffer)
     {
-        uint inputCrc = this.ReadChunkCrc();
+        uint inputCrc = this.ReadChunkCrc(buffer);
 
         if (chunk.IsCritical)
         {
@@ -1513,13 +1517,14 @@ internal sealed class PngDecoderCore : IImageDecoderInternals
     /// <summary>
     /// Reads the cycle redundancy chunk from the data.
     /// </summary>
+    /// <param name="buffer">Temporary buffer.</param>
     [MethodImpl(InliningOptions.ShortMethod)]
-    private uint ReadChunkCrc()
+    private uint ReadChunkCrc(Span<byte> buffer)
     {
         uint crc = 0;
-        if (this.currentStream.Read(this.buffer, 0, 4) == 4)
+        if (this.currentStream.Read(buffer, 0, 4) == 4)
         {
-            crc = BinaryPrimitives.ReadUInt32BigEndian(this.buffer);
+            crc = BinaryPrimitives.ReadUInt32BigEndian(buffer);
         }
 
         return crc;
@@ -1554,15 +1559,16 @@ internal sealed class PngDecoderCore : IImageDecoderInternals
     /// <summary>
     /// Identifies the chunk type from the chunk.
     /// </summary>
+    /// <param name="buffer">Temporary buffer.</param>
     /// <exception cref="ImageFormatException">
     /// Thrown if the input stream is not valid.
     /// </exception>
     [MethodImpl(InliningOptions.ShortMethod)]
-    private PngChunkType ReadChunkType()
+    private PngChunkType ReadChunkType(Span<byte> buffer)
     {
-        if (this.currentStream.Read(this.buffer, 0, 4) == 4)
+        if (this.currentStream.Read(buffer, 0, 4) == 4)
         {
-            return (PngChunkType)BinaryPrimitives.ReadUInt32BigEndian(this.buffer);
+            return (PngChunkType)BinaryPrimitives.ReadUInt32BigEndian(buffer);
         }
 
         PngThrowHelper.ThrowInvalidChunkType();
@@ -1574,16 +1580,17 @@ internal sealed class PngDecoderCore : IImageDecoderInternals
     /// <summary>
     /// Attempts to read the length of the next chunk.
     /// </summary>
+    /// <param name="buffer">Temporary buffer.</param>
     /// <param name="result">The result length. If the return type is <see langword="false"/> this parameter is passed uninitialized.</param>
     /// <returns>
     /// Whether the length was read.
     /// </returns>
     [MethodImpl(InliningOptions.ShortMethod)]
-    private bool TryReadChunkLength(out int result)
+    private bool TryReadChunkLength(Span<byte> buffer, out int result)
     {
-        if (this.currentStream.Read(this.buffer, 0, 4) == 4)
+        if (this.currentStream.Read(buffer, 0, 4) == 4)
         {
-            result = BinaryPrimitives.ReadInt32BigEndian(this.buffer);
+            result = BinaryPrimitives.ReadInt32BigEndian(buffer);
 
             return true;
         }

src/ImageSharp/Formats/Png/PngEncoderCore.cs

@@ -38,15 +38,10 @@ internal sealed class PngEncoderCore : IImageEncoderInternals, IDisposable
     /// </summary>
     private readonly Configuration configuration;
 
-    /// <summary>
-    /// Reusable buffer for writing general data.
-    /// </summary>
-    private readonly byte[] buffer = new byte[8];
-
     /// <summary>
     /// Reusable buffer for writing chunk data.
     /// </summary>
-    private readonly byte[] chunkDataBuffer = new byte[16];
+    private ScratchBuffer chunkDataBuffer;  // mutable struct, don't make readonly
 
     /// <summary>
     /// The encoder with options
@@ -576,9 +571,9 @@ internal sealed class PngEncoderCore : IImageEncoderInternals, IDisposable
             filterMethod: 0,
             interlaceMethod: this.interlaceMode);
 
-        header.WriteTo(this.chunkDataBuffer);
+        header.WriteTo(this.chunkDataBuffer.Span);
 
-        this.WriteChunk(stream, PngChunkType.Header, this.chunkDataBuffer, 0, PngHeader.Size);
+        this.WriteChunk(stream, PngChunkType.Header, this.chunkDataBuffer.Span, 0, PngHeader.Size);
     }
 
     /// <summary>
@@ -652,9 +647,9 @@ internal sealed class PngEncoderCore : IImageEncoderInternals, IDisposable
             return;
         }
 
-        PhysicalChunkData.FromMetadata(meta).WriteTo(this.chunkDataBuffer);
+        PhysicalChunkData.FromMetadata(meta).WriteTo(this.chunkDataBuffer.Span);
 
-        this.WriteChunk(stream, PngChunkType.Physical, this.chunkDataBuffer, 0, PhysicalChunkData.Size);
+        this.WriteChunk(stream, PngChunkType.Physical, this.chunkDataBuffer.Span, 0, PhysicalChunkData.Size);
     }
 
     /// <summary>
@@ -880,9 +875,9 @@ internal sealed class PngEncoderCore : IImageEncoderInternals, IDisposable
             // 4-byte unsigned integer of gamma * 100,000.
             uint gammaValue = (uint)(this.gamma * 100_000F);
 
-            BinaryPrimitives.WriteUInt32BigEndian(this.chunkDataBuffer.AsSpan(0, 4), gammaValue);
+            BinaryPrimitives.WriteUInt32BigEndian(this.chunkDataBuffer.Span.Slice(0, 4), gammaValue);
 
-            this.WriteChunk(stream, PngChunkType.Gamma, this.chunkDataBuffer, 0, 4);
+            this.WriteChunk(stream, PngChunkType.Gamma, this.chunkDataBuffer.Span, 0, 4);
         }
     }
 
@@ -899,7 +894,7 @@ internal sealed class PngEncoderCore : IImageEncoderInternals, IDisposable
             return;
         }
 
-        Span<byte> alpha = this.chunkDataBuffer.AsSpan();
+        Span<byte> alpha = this.chunkDataBuffer.Span;
         if (pngMetadata.ColorType == PngColorType.Rgb)
         {
             if (pngMetadata.TransparentRgb48.HasValue && this.use16Bit)
@@ -909,7 +904,7 @@ internal sealed class PngEncoderCore : IImageEncoderInternals, IDisposable
                 BinaryPrimitives.WriteUInt16LittleEndian(alpha.Slice(2, 2), rgb.G);
                 BinaryPrimitives.WriteUInt16LittleEndian(alpha.Slice(4, 2), rgb.B);
 
-                this.WriteChunk(stream, PngChunkType.Transparency, this.chunkDataBuffer, 0, 6);
+                this.WriteChunk(stream, PngChunkType.Transparency, this.chunkDataBuffer.Span, 0, 6);
             }
             else if (pngMetadata.TransparentRgb24.HasValue)
             {
@@ -918,7 +913,7 @@ internal sealed class PngEncoderCore : IImageEncoderInternals, IDisposable
                 alpha[1] = rgb.R;
                 alpha[3] = rgb.G;
                 alpha[5] = rgb.B;
-                this.WriteChunk(stream, PngChunkType.Transparency, this.chunkDataBuffer, 0, 6);
+                this.WriteChunk(stream, PngChunkType.Transparency, this.chunkDataBuffer.Span, 0, 6);
             }
         }
         else if (pngMetadata.ColorType == PngColorType.Grayscale)
@@ -926,13 +921,13 @@ internal sealed class PngEncoderCore : IImageEncoderInternals, IDisposable
             if (pngMetadata.TransparentL16.HasValue && this.use16Bit)
             {
                 BinaryPrimitives.WriteUInt16LittleEndian(alpha, pngMetadata.TransparentL16.Value.PackedValue);
-                this.WriteChunk(stream, PngChunkType.Transparency, this.chunkDataBuffer, 0, 2);
+                this.WriteChunk(stream, PngChunkType.Transparency, this.chunkDataBuffer.Span, 0, 2);
             }
             else if (pngMetadata.TransparentL8.HasValue)
             {
                 alpha.Clear();
                 alpha[1] = pngMetadata.TransparentL8.Value.PackedValue;
-                this.WriteChunk(stream, PngChunkType.Transparency, this.chunkDataBuffer, 0, 2);
+                this.WriteChunk(stream, PngChunkType.Transparency, this.chunkDataBuffer.Span, 0, 2);
             }
         }
     }
@@ -1173,12 +1168,14 @@ internal sealed class PngEncoderCore : IImageEncoderInternals, IDisposable
     /// <param name="length">The of the data to write.</param>
     private void WriteChunk(Stream stream, PngChunkType type, Span<byte> data, int offset, int length)
     {
-        BinaryPrimitives.WriteInt32BigEndian(this.buffer, length);
-        BinaryPrimitives.WriteUInt32BigEndian(this.buffer.AsSpan(4, 4), (uint)type);
+        Span<byte> buffer = stackalloc byte[8];
+
+        BinaryPrimitives.WriteInt32BigEndian(buffer, length);
+        BinaryPrimitives.WriteUInt32BigEndian(buffer.Slice(4, 4), (uint)type);
 
-        stream.Write(this.buffer, 0, 8);
+        stream.Write(buffer);
 
-        uint crc = Crc32.Calculate(this.buffer.AsSpan(4, 4)); // Write the type buffer
+        uint crc = Crc32.Calculate(buffer.Slice(4)); // Write the type buffer
 
         if (data.Length > 0 && length > 0)
         {
@@ -1187,9 +1184,9 @@ internal sealed class PngEncoderCore : IImageEncoderInternals, IDisposable
             crc = Crc32.Calculate(crc, data.Slice(offset, length));
         }
 
-        BinaryPrimitives.WriteUInt32BigEndian(this.buffer, crc);
+        BinaryPrimitives.WriteUInt32BigEndian(buffer, crc);
 
-        stream.Write(this.buffer, 0, 4); // write the crc
+        stream.Write(buffer, 0, 4); // write the crc
     }
 
     /// <summary>
@@ -1412,4 +1409,12 @@ internal sealed class PngEncoderCore : IImageEncoderInternals, IDisposable
             Type t when t == typeof(RgbaVector) => PngBitDepth.Bit16,
             _ => PngBitDepth.Bit8
         };
+
+    private unsafe struct ScratchBuffer
+    {
+        private const int Size = 16;
+        private fixed byte scratch[Size];
+
+        public Span<byte> Span => MemoryMarshal.CreateSpan(ref this.scratch[0], Size);
+    }
 }

src/ImageSharp/Formats/Tga/TgaDecoderCore.cs

@@ -17,11 +17,6 @@ namespace SixLabors.ImageSharp.Formats.Tga;
 /// </summary>
 internal sealed class TgaDecoderCore : IImageDecoderInternals
 {
-    /// <summary>
-    /// A scratch buffer to reduce allocations.
-    /// </summary>
-    private readonly byte[] scratchBuffer = new byte[4];
-
     /// <summary>
     /// General configuration options.
     /// </summary>
@@ -407,6 +402,7 @@ internal sealed class TgaDecoderCore : IImageDecoderInternals
         bool invertX = InvertX(origin);
         using IMemoryOwner<byte> row = this.memoryAllocator.AllocatePaddedPixelRowBuffer(width, 2, 0);
         Span<byte> rowSpan = row.GetSpan();
+        Span<byte> scratchBuffer = stackalloc byte[2];
 
         for (int y = 0; y < height; y++)
         {
@@ -417,7 +413,7 @@ internal sealed class TgaDecoderCore : IImageDecoderInternals
             {
                 for (int x = width - 1; x >= 0; x--)
                 {
-                    int bytesRead = stream.Read(this.scratchBuffer, 0, 2);
+                    int bytesRead = stream.Read(scratchBuffer);
                     if (bytesRead != 2)
                     {
                         TgaThrowHelper.ThrowInvalidImageContentException("Not enough data to read a pixel row");
@@ -425,16 +421,16 @@ internal sealed class TgaDecoderCore : IImageDecoderInternals
 
                     if (!this.hasAlpha)
                     {
-                        this.scratchBuffer[1] |= 1 << 7;
+                        scratchBuffer[1] |= 1 << 7;
                     }
 
                     if (this.fileHeader.ImageType == TgaImageType.BlackAndWhite)
                     {
-                        color.FromLa16(Unsafe.As<byte, La16>(ref MemoryMarshal.GetArrayDataReference(this.scratchBuffer)));
+                        color.FromLa16(Unsafe.As<byte, La16>(ref MemoryMarshal.GetReference(scratchBuffer)));
                     }
                     else
                     {
-                        color.FromBgra5551(Unsafe.As<byte, Bgra5551>(ref MemoryMarshal.GetArrayDataReference(this.scratchBuffer)));
+                        color.FromBgra5551(Unsafe.As<byte, Bgra5551>(ref MemoryMarshal.GetReference(scratchBuffer)));
                     }
 
                     pixelSpan[x] = color;
@@ -484,6 +480,7 @@ internal sealed class TgaDecoderCore : IImageDecoderInternals
         bool invertX = InvertX(origin);
         if (invertX)
         {
+            Span<byte> scratchBuffer = stackalloc byte[4];
             TPixel color = default;
             for (int y = 0; y < height; y++)
             {
@@ -491,7 +488,7 @@ internal sealed class TgaDecoderCore : IImageDecoderInternals
                 Span<TPixel> pixelSpan = pixels.DangerousGetRowSpan(newY);
                 for (int x = width - 1; x >= 0; x--)
                 {
-                    this.ReadBgr24Pixel(stream, color, x, pixelSpan);
+                    ReadBgr24Pixel(stream, color, x, pixelSpan, scratchBuffer);
                 }
             }
 
@@ -558,6 +555,8 @@ internal sealed class TgaDecoderCore : IImageDecoderInternals
             return;
         }
 
+        Span<byte> scratchBuffer = stackalloc byte[4];
+
         for (int y = 0; y < height; y++)
         {
             int newY = InvertY(y, height, origin);
@@ -566,14 +565,14 @@ internal sealed class TgaDecoderCore : IImageDecoderInternals
             {
                 for (int x = width - 1; x >= 0; x--)
                 {
-                    this.ReadBgra32Pixel(stream, x, color, pixelRow);
+                    this.ReadBgra32Pixel(stream, x, color, pixelRow, scratchBuffer);
                 }
             }
             else
             {
                 for (int x = 0; x < width; x++)
                 {
-                    this.ReadBgra32Pixel(stream, x, color, pixelRow);
+                    this.ReadBgra32Pixel(stream, x, color, pixelRow, scratchBuffer);
                 }
             }
         }
@@ -687,16 +686,16 @@ internal sealed class TgaDecoderCore : IImageDecoderInternals
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    private void ReadBgr24Pixel<TPixel>(BufferedReadStream stream, TPixel color, int x, Span<TPixel> pixelSpan)
+    private static void ReadBgr24Pixel<TPixel>(BufferedReadStream stream, TPixel color, int x, Span<TPixel> pixelSpan, Span<byte> scratchBuffer)
         where TPixel : unmanaged, IPixel<TPixel>
     {
-        int bytesRead = stream.Read(this.scratchBuffer, 0, 3);
+        int bytesRead = stream.Read(scratchBuffer, 0, 3);
         if (bytesRead != 3)
         {
             TgaThrowHelper.ThrowInvalidImageContentException("Not enough data to read a bgr pixel");
         }
 
-        color.FromBgr24(Unsafe.As<byte, Bgr24>(ref MemoryMarshal.GetArrayDataReference(this.scratchBuffer)));
+        color.FromBgr24(Unsafe.As<byte, Bgr24>(ref MemoryMarshal.GetReference(scratchBuffer)));
         pixelSpan[x] = color;
     }
 
@@ -715,10 +714,10 @@ internal sealed class TgaDecoderCore : IImageDecoderInternals
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    private void ReadBgra32Pixel<TPixel>(BufferedReadStream stream, int x, TPixel color, Span<TPixel> pixelRow)
+    private void ReadBgra32Pixel<TPixel>(BufferedReadStream stream, int x, TPixel color, Span<TPixel> pixelRow, Span<byte> scratchBuffer)
         where TPixel : unmanaged, IPixel<TPixel>
     {
-        int bytesRead = stream.Read(this.scratchBuffer, 0, 4);
+        int bytesRead = stream.Read(scratchBuffer, 0, 4);
         if (bytesRead != 4)
         {
             TgaThrowHelper.ThrowInvalidImageContentException("Not enough data to read a bgra pixel");
@@ -726,8 +725,8 @@ internal sealed class TgaDecoderCore : IImageDecoderInternals
 
         Guard.NotNull(this.tgaMetadata);
 
-        byte alpha = this.tgaMetadata.AlphaChannelBits == 0 ? byte.MaxValue : this.scratchBuffer[3];
-        color.FromBgra32(new Bgra32(this.scratchBuffer[2], this.scratchBuffer[1], this.scratchBuffer[0], alpha));
+        byte alpha = this.tgaMetadata.AlphaChannelBits == 0 ? byte.MaxValue : scratchBuffer[3];
+        color.FromBgra32(new Bgra32(scratchBuffer[2], scratchBuffer[1], scratchBuffer[0], alpha));
         pixelRow[x] = color;
     }
 
@@ -814,7 +813,7 @@ internal sealed class TgaDecoderCore : IImageDecoderInternals
     private void UncompressRle(BufferedReadStream stream, int width, int height, Span<byte> buffer, int bytesPerPixel)
     {
         int uncompressedPixels = 0;
-        Span<byte> pixel = this.scratchBuffer.AsSpan(0, bytesPerPixel);
+        Span<byte> pixel = stackalloc byte[bytesPerPixel];
         int totalPixels = width * height;
         while (uncompressedPixels < totalPixels)
         {
@@ -825,7 +824,7 @@ internal sealed class TgaDecoderCore : IImageDecoderInternals
             if (highBit == 1)
             {
                 int runLength = runLengthByte & 127;
-                int bytesRead = stream.Read(pixel, 0, bytesPerPixel);
+                int bytesRead = stream.Read(pixel);
                 if (bytesRead != bytesPerPixel)
                 {
                     TgaThrowHelper.ThrowInvalidImageContentException("Not enough data to read a pixel from the stream");
@@ -845,7 +844,7 @@ internal sealed class TgaDecoderCore : IImageDecoderInternals
                 int bufferIdx = uncompressedPixels * bytesPerPixel;
                 for (int i = 0; i < runLength + 1; i++, uncompressedPixels++)
                 {
-                    int bytesRead = stream.Read(pixel, 0, bytesPerPixel);
+                    int bytesRead = stream.Read(pixel);
                     if (bytesRead != bytesPerPixel)
                     {
                         TgaThrowHelper.ThrowInvalidImageContentException("Not enough data to read a pixel from the stream");

src/ImageSharp/Formats/Tga/TgaEncoderCore.cs

@@ -22,11 +22,6 @@ internal sealed class TgaEncoderCore : IImageEncoderInternals
     /// </summary>
     private readonly MemoryAllocator memoryAllocator;
 
-    /// <summary>
-    /// Reusable buffer for writing data.
-    /// </summary>
-    private readonly byte[] buffer = new byte[2];
-
     /// <summary>
     /// The color depth, in number of bits per pixel.
     /// </summary>
@@ -221,9 +216,10 @@ internal sealed class TgaEncoderCore : IImageEncoderInternals
 
             case TgaBitsPerPixel.Pixel16:
                 Bgra5551 bgra5551 = new(color.ToVector4());
-                BinaryPrimitives.WriteInt16LittleEndian(this.buffer, (short)bgra5551.PackedValue);
-                stream.WriteByte(this.buffer[0]);
-                stream.WriteByte(this.buffer[1]);
+                Span<byte> buffer = stackalloc byte[2];
+                BinaryPrimitives.WriteInt16LittleEndian(buffer, (short)bgra5551.PackedValue);
+                stream.WriteByte(buffer[0]);
+                stream.WriteByte(buffer[1]);
 
                 break;
 

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/BlackIsZero32FloatTiffColor{TPixel}.cs

@@ -24,9 +24,9 @@ internal class BlackIsZero32FloatTiffColor<TPixel> : TiffBaseColorDecoder<TPixel
     /// <inheritdoc/>
     public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, int left, int top, int width, int height)
     {
-        var color = default(TPixel);
+        TPixel color = default;
         color.FromScaledVector4(Vector4.Zero);
-        byte[] buffer = new byte[4];
+        Span<byte> buffer = stackalloc byte[4];
 
         int offset = 0;
         for (int y = top; y < top + height; y++)
@@ -37,8 +37,8 @@ internal class BlackIsZero32FloatTiffColor<TPixel> : TiffBaseColorDecoder<TPixel
                 for (int x = 0; x < pixelRow.Length; x++)
                 {
                     data.Slice(offset, 4).CopyTo(buffer);
-                    Array.Reverse(buffer);
-                    float intensity = BitConverter.ToSingle(buffer, 0);
+                    buffer.Reverse();
+                    float intensity = BitConverter.ToSingle(buffer);
                     offset += 4;
 
                     var colorVector = new Vector4(intensity, intensity, intensity, 1.0f);
@@ -50,8 +50,7 @@ internal class BlackIsZero32FloatTiffColor<TPixel> : TiffBaseColorDecoder<TPixel
             {
                 for (int x = 0; x < pixelRow.Length; x++)
                 {
-                    data.Slice(offset, 4).CopyTo(buffer);
-                    float intensity = BitConverter.ToSingle(buffer, 0);
+                    float intensity = BitConverter.ToSingle(data.Slice(offset, 4));
                     offset += 4;
 
                     var colorVector = new Vector4(intensity, intensity, intensity, 1.0f);

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/RgbFloat323232TiffColor{TPixel}.cs

@@ -27,7 +27,7 @@ internal class RgbFloat323232TiffColor<TPixel> : TiffBaseColorDecoder<TPixel>
         var color = default(TPixel);
         color.FromScaledVector4(Vector4.Zero);
         int offset = 0;
-        byte[] buffer = new byte[4];
+        Span<byte> buffer = stackalloc byte[4];
 
         for (int y = top; y < top + height; y++)
         {
@@ -38,18 +38,18 @@ internal class RgbFloat323232TiffColor<TPixel> : TiffBaseColorDecoder<TPixel>
                 for (int x = 0; x < pixelRow.Length; x++)
                 {
                     data.Slice(offset, 4).CopyTo(buffer);
-                    Array.Reverse(buffer);
-                    float r = BitConverter.ToSingle(buffer, 0);
+                    buffer.Reverse();
+                    float r = BitConverter.ToSingle(buffer);
                     offset += 4;
 
                     data.Slice(offset, 4).CopyTo(buffer);
-                    Array.Reverse(buffer);
-                    float g = BitConverter.ToSingle(buffer, 0);
+                    buffer.Reverse();
+                    float g = BitConverter.ToSingle(buffer);
                     offset += 4;
 
                     data.Slice(offset, 4).CopyTo(buffer);
-                    Array.Reverse(buffer);
-                    float b = BitConverter.ToSingle(buffer, 0);
+                    buffer.Reverse();
+                    float b = BitConverter.ToSingle(buffer);
                     offset += 4;
 
                     var colorVector = new Vector4(r, g, b, 1.0f);
@@ -61,16 +61,13 @@ internal class RgbFloat323232TiffColor<TPixel> : TiffBaseColorDecoder<TPixel>
             {
                 for (int x = 0; x < pixelRow.Length; x++)
                 {
-                    data.Slice(offset, 4).CopyTo(buffer);
-                    float r = BitConverter.ToSingle(buffer, 0);
+                    float r = BitConverter.ToSingle(data.Slice(offset, 4));
                     offset += 4;
 
-                    data.Slice(offset, 4).CopyTo(buffer);
-                    float g = BitConverter.ToSingle(buffer, 0);
+                    float g = BitConverter.ToSingle(data.Slice(offset, 4));
                     offset += 4;
 
-                    data.Slice(offset, 4).CopyTo(buffer);
-                    float b = BitConverter.ToSingle(buffer, 0);
+                    float b = BitConverter.ToSingle(data.Slice(offset, 4));
                     offset += 4;
 
                     var colorVector = new Vector4(r, g, b, 1.0f);

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/RgbaFloat32323232TiffColor{TPixel}.cs

@@ -27,7 +27,7 @@ internal class RgbaFloat32323232TiffColor<TPixel> : TiffBaseColorDecoder<TPixel>
         var color = default(TPixel);
         color.FromScaledVector4(Vector4.Zero);
         int offset = 0;
-        byte[] buffer = new byte[4];
+        Span<byte> buffer = stackalloc byte[4];
 
         for (int y = top; y < top + height; y++)
         {
@@ -38,23 +38,23 @@ internal class RgbaFloat32323232TiffColor<TPixel> : TiffBaseColorDecoder<TPixel>
                 for (int x = 0; x < pixelRow.Length; x++)
                 {
                     data.Slice(offset, 4).CopyTo(buffer);
-                    Array.Reverse(buffer);
-                    float r = BitConverter.ToSingle(buffer, 0);
+                    buffer.Reverse();
+                    float r = BitConverter.ToSingle(buffer);
                     offset += 4;
 
                     data.Slice(offset, 4).CopyTo(buffer);
-                    Array.Reverse(buffer);
-                    float g = BitConverter.ToSingle(buffer, 0);
+                    buffer.Reverse();
+                    float g = BitConverter.ToSingle(buffer);
                     offset += 4;
 
                     data.Slice(offset, 4).CopyTo(buffer);
-                    Array.Reverse(buffer);
-                    float b = BitConverter.ToSingle(buffer, 0);
+                    buffer.Reverse();
+                    float b = BitConverter.ToSingle(buffer);
                     offset += 4;
 
                     data.Slice(offset, 4).CopyTo(buffer);
-                    Array.Reverse(buffer);
-                    float a = BitConverter.ToSingle(buffer, 0);
+                    buffer.Reverse();
+                    float a = BitConverter.ToSingle(buffer);
                     offset += 4;
 
                     var colorVector = new Vector4(r, g, b, a);
@@ -66,20 +66,16 @@ internal class RgbaFloat32323232TiffColor<TPixel> : TiffBaseColorDecoder<TPixel>
             {
                 for (int x = 0; x < pixelRow.Length; x++)
                 {
-                    data.Slice(offset, 4).CopyTo(buffer);
-                    float r = BitConverter.ToSingle(buffer, 0);
+                    float r = BitConverter.ToSingle(data.Slice(offset, 4));
                     offset += 4;
 
-                    data.Slice(offset, 4).CopyTo(buffer);
-                    float g = BitConverter.ToSingle(buffer, 0);
+                    float g = BitConverter.ToSingle(data.Slice(offset, 4));
                     offset += 4;
 
-                    data.Slice(offset, 4).CopyTo(buffer);
-                    float b = BitConverter.ToSingle(buffer, 0);
+                    float b = BitConverter.ToSingle(data.Slice(offset, 4));
                     offset += 4;
 
-                    data.Slice(offset, 4).CopyTo(buffer);
-                    float a = BitConverter.ToSingle(buffer, 0);
+                    float a = BitConverter.ToSingle(data.Slice(offset, 4));
                     offset += 4;
 
                     var colorVector = new Vector4(r, g, b, a);

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/WhiteIsZero32FloatTiffColor{TPixel}.cs

@@ -26,7 +26,7 @@ internal class WhiteIsZero32FloatTiffColor<TPixel> : TiffBaseColorDecoder<TPixel
     {
         var color = default(TPixel);
         color.FromScaledVector4(Vector4.Zero);
-        byte[] buffer = new byte[4];
+        Span<byte> buffer = stackalloc byte[4];
 
         int offset = 0;
         for (int y = top; y < top + height; y++)
@@ -37,8 +37,8 @@ internal class WhiteIsZero32FloatTiffColor<TPixel> : TiffBaseColorDecoder<TPixel
                 for (int x = 0; x < pixelRow.Length; x++)
                 {
                     data.Slice(offset, 4).CopyTo(buffer);
-                    Array.Reverse(buffer);
-                    float intensity = 1.0f - BitConverter.ToSingle(buffer, 0);
+                    buffer.Reverse();
+                    float intensity = 1.0f - BitConverter.ToSingle(buffer);
                     offset += 4;
 
                     var colorVector = new Vector4(intensity, intensity, intensity, 1.0f);
@@ -50,8 +50,7 @@ internal class WhiteIsZero32FloatTiffColor<TPixel> : TiffBaseColorDecoder<TPixel
             {
                 for (int x = 0; x < pixelRow.Length; x++)
                 {
-                    data.Slice(offset, 4).CopyTo(buffer);
-                    float intensity = 1.0f - BitConverter.ToSingle(buffer, 0);
+                    float intensity = 1.0f - BitConverter.ToSingle(data.Slice(offset, 4));
                     offset += 4;
 
                     var colorVector = new Vector4(intensity, intensity, intensity, 1.0f);

src/ImageSharp/Formats/Tiff/TiffEncoderCore.cs

@@ -29,11 +29,6 @@ internal sealed class TiffEncoderCore : IImageEncoderInternals
     /// </summary>
     private readonly MemoryAllocator memoryAllocator;
 
-    /// <summary>
-    /// A scratch buffer to reduce allocations.
-    /// </summary>
-    private readonly byte[] buffer = new byte[4];
-
     /// <summary>
     /// The global configuration.
     /// </summary>
@@ -157,7 +152,9 @@ internal sealed class TiffEncoderCore : IImageEncoderInternals
         this.SanitizeAndSetEncoderOptions(bitsPerPixel, image.PixelType.BitsPerPixel, photometricInterpretation, compression, predictor);
 
         using TiffStreamWriter writer = new(stream);
-        long ifdMarker = WriteHeader(writer);
+        Span<byte> buffer = stackalloc byte[4];
+
+        long ifdMarker = WriteHeader(writer, buffer);
 
         Image<TPixel> metadataImage = image;
         foreach (ImageFrame<TPixel> frame in image.Frames)
@@ -171,7 +168,7 @@ internal sealed class TiffEncoderCore : IImageEncoderInternals
         long currentOffset = writer.BaseStream.Position;
         foreach ((long, uint) marker in this.frameMarkers)
         {
-            writer.WriteMarkerFast(marker.Item1, marker.Item2);
+            writer.WriteMarkerFast(marker.Item1, marker.Item2, buffer);
         }
 
         writer.BaseStream.Seek(currentOffset, SeekOrigin.Begin);
@@ -181,14 +178,15 @@ internal sealed class TiffEncoderCore : IImageEncoderInternals
     /// Writes the TIFF file header.
     /// </summary>
     /// <param name="writer">The <see cref="TiffStreamWriter" /> to write data to.</param>
+    /// <param name="buffer">Scratch buffer with minimum size of 2.</param>
     /// <returns>
     /// The marker to write the first IFD offset.
     /// </returns>
-    public static long WriteHeader(TiffStreamWriter writer)
+    public static long WriteHeader(TiffStreamWriter writer, Span<byte> buffer)
     {
-        writer.Write(ByteOrderMarker);
-        writer.Write(TiffConstants.HeaderMagicNumber);
-        return writer.PlaceMarker();
+        writer.Write(ByteOrderMarker, buffer);
+        writer.Write(TiffConstants.HeaderMagicNumber, buffer);
+        return writer.PlaceMarker(buffer);
     }
 
     /// <summary>
@@ -307,20 +305,22 @@ internal sealed class TiffEncoderCore : IImageEncoderInternals
 
         entries.Sort((a, b) => (ushort)a.Tag - (ushort)b.Tag);
 
-        writer.Write((ushort)entries.Count);
+        Span<byte> buffer = stackalloc byte[4];
+
+        writer.Write((ushort)entries.Count, buffer);
 
         foreach (IExifValue entry in entries)
         {
-            writer.Write((ushort)entry.Tag);
-            writer.Write((ushort)entry.DataType);
-            writer.Write(ExifWriter.GetNumberOfComponents(entry));
+            writer.Write((ushort)entry.Tag, buffer);
+            writer.Write((ushort)entry.DataType, buffer);
+            writer.Write(ExifWriter.GetNumberOfComponents(entry), buffer);
 
             uint length = ExifWriter.GetLength(entry);
             if (length <= 4)
             {
-                int sz = ExifWriter.WriteValue(entry, this.buffer, 0);
+                int sz = ExifWriter.WriteValue(entry, buffer, 0);
                 DebugGuard.IsTrue(sz == length, "Incorrect number of bytes written");
-                writer.WritePadded(this.buffer.AsSpan(0, sz));
+                writer.WritePadded(buffer.Slice(0, sz));
             }
             else
             {
@@ -328,12 +328,12 @@ internal sealed class TiffEncoderCore : IImageEncoderInternals
                 int sz = ExifWriter.WriteValue(entry, raw, 0);
                 DebugGuard.IsTrue(sz == raw.Length, "Incorrect number of bytes written");
                 largeDataBlocks.Add(raw);
-                writer.Write(dataOffset);
+                writer.Write(dataOffset, buffer);
                 dataOffset += (uint)(raw.Length + (raw.Length % 2));
             }
         }
 
-        long nextIfdMarker = writer.PlaceMarker();
+        long nextIfdMarker = writer.PlaceMarker(buffer);
 
         foreach (byte[] dataBlock in largeDataBlocks)
         {

src/ImageSharp/Formats/Tiff/Writers/TiffStreamWriter.cs

@@ -10,13 +10,6 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Writers;
 /// </summary>
 internal sealed class TiffStreamWriter : IDisposable
 {
-    private static readonly byte[] PaddingBytes = new byte[4];
-
-    /// <summary>
-    /// A scratch buffer to reduce allocations.
-    /// </summary>
-    private readonly byte[] buffer = new byte[4];
-
     /// <summary>
     /// Initializes a new instance of the <see cref="TiffStreamWriter"/> class.
     /// </summary>
@@ -41,11 +34,12 @@ internal sealed class TiffStreamWriter : IDisposable
     /// <summary>
     /// Writes an empty four bytes to the stream, returning the offset to be written later.
     /// </summary>
+    /// <param name="buffer">Scratch buffer with minimum size of 4.</param>
     /// <returns>The offset to be written later.</returns>
-    public long PlaceMarker()
+    public long PlaceMarker(Span<byte> buffer)
     {
         long offset = this.BaseStream.Position;
-        this.Write(0u);
+        this.Write(0u, buffer);
         return offset;
     }
 
@@ -71,36 +65,38 @@ internal sealed class TiffStreamWriter : IDisposable
     /// Writes a two-byte unsigned integer to the current stream.
     /// </summary>
     /// <param name="value">The two-byte unsigned integer to write.</param>
-    public void Write(ushort value)
+    /// <param name="buffer">Scratch buffer with minimum size of 2.</param>
+    public void Write(ushort value, Span<byte> buffer)
     {
         if (IsLittleEndian)
         {
-            BinaryPrimitives.WriteUInt16LittleEndian(this.buffer, value);
+            BinaryPrimitives.WriteUInt16LittleEndian(buffer, value);
         }
         else
         {
-            BinaryPrimitives.WriteUInt16BigEndian(this.buffer, value);
+            BinaryPrimitives.WriteUInt16BigEndian(buffer, value);
         }
 
-        this.BaseStream.Write(this.buffer.AsSpan(0, 2));
+        this.BaseStream.Write(buffer.Slice(0, 2));
     }
 
     /// <summary>
     /// Writes a four-byte unsigned integer to the current stream.
     /// </summary>
     /// <param name="value">The four-byte unsigned integer to write.</param>
-    public void Write(uint value)
+    /// <param name="buffer">Scratch buffer with minimum size of 4.</param>
+    public void Write(uint value, Span<byte> buffer)
     {
         if (IsLittleEndian)
         {
-            BinaryPrimitives.WriteUInt32LittleEndian(this.buffer, value);
+            BinaryPrimitives.WriteUInt32LittleEndian(buffer, value);
         }
         else
         {
-            BinaryPrimitives.WriteUInt32BigEndian(this.buffer, value);
+            BinaryPrimitives.WriteUInt32BigEndian(buffer, value);
         }
 
-        this.BaseStream.Write(this.buffer.AsSpan(0, 4));
+        this.BaseStream.Write(buffer.Slice(0, 4));
     }
 
     /// <summary>
@@ -113,7 +109,10 @@ internal sealed class TiffStreamWriter : IDisposable
 
         if (value.Length % 4 != 0)
         {
-            this.BaseStream.Write(PaddingBytes, 0, 4 - (value.Length % 4));
+            // No allocation occurs, refers directly to assembly's data segment.
+            ReadOnlySpan<byte> paddingBytes = new byte[4] { 0x00, 0x00, 0x00, 0x00 };
+            paddingBytes = paddingBytes[..(4 - (value.Length % 4))];
+            this.BaseStream.Write(paddingBytes);
         }
     }
 
@@ -122,18 +121,19 @@ internal sealed class TiffStreamWriter : IDisposable
     /// </summary>
     /// <param name="offset">The offset returned when placing the marker</param>
     /// <param name="value">The four-byte unsigned integer to write.</param>
-    public void WriteMarker(long offset, uint value)
+    /// <param name="buffer">Scratch buffer.</param>
+    public void WriteMarker(long offset, uint value, Span<byte> buffer)
     {
         long back = this.BaseStream.Position;
         this.BaseStream.Seek(offset, SeekOrigin.Begin);
-        this.Write(value);
+        this.Write(value, buffer);
         this.BaseStream.Seek(back, SeekOrigin.Begin);
     }
 
-    public void WriteMarkerFast(long offset, uint value)
+    public void WriteMarkerFast(long offset, uint value, Span<byte> buffer)
     {
         this.BaseStream.Seek(offset, SeekOrigin.Begin);
-        this.Write(value);
+        this.Write(value, buffer);
     }
 
     /// <summary>

src/ImageSharp/Formats/Webp/BitReader/Vp8LBitReader.cs

@@ -192,7 +192,7 @@ internal class Vp8LBitReader : BitReaderBase
     [MethodImpl(InliningOptions.ShortMethod)]
     private void ShiftBytes()
     {
-        System.Span<byte> dataSpan = this.Data!.Memory.Span;
+        Span<byte> dataSpan = this.Data!.Memory.Span;
         while (this.bitPos >= 8 && this.pos < this.len)
         {
             this.value >>= 8;

src/ImageSharp/Formats/Webp/BitWriter/BitWriterBase.cs

@@ -2,6 +2,7 @@
 // Licensed under the Six Labors Split License.
 
 using System.Buffers.Binary;
+using System.Runtime.InteropServices;
 using SixLabors.ImageSharp.Metadata.Profiles.Exif;
 using SixLabors.ImageSharp.Metadata.Profiles.Xmp;
 
@@ -23,7 +24,7 @@ internal abstract class BitWriterBase
     /// <summary>
     /// A scratch buffer to reduce allocations.
     /// </summary>
-    private readonly byte[] scratchBuffer = new byte[4];
+    private ScratchBuffer scratchBuffer;  // mutable struct, don't make readonly
 
     /// <summary>
     /// Initializes a new instance of the <see cref="BitWriterBase"/> class.
@@ -90,8 +91,8 @@ internal abstract class BitWriterBase
     protected void WriteRiffHeader(Stream stream, uint riffSize)
     {
         stream.Write(WebpConstants.RiffFourCc);
-        BinaryPrimitives.WriteUInt32LittleEndian(this.scratchBuffer, riffSize);
-        stream.Write(this.scratchBuffer.AsSpan(0, 4));
+        BinaryPrimitives.WriteUInt32LittleEndian(this.scratchBuffer.Span, riffSize);
+        stream.Write(this.scratchBuffer.Span.Slice(0, 4));
         stream.Write(WebpConstants.WebpHeader);
     }
 
@@ -128,7 +129,7 @@ internal abstract class BitWriterBase
         DebugGuard.NotNull(metadataBytes, nameof(metadataBytes));
 
         uint size = (uint)metadataBytes.Length;
-        Span<byte> buf = this.scratchBuffer.AsSpan(0, 4);
+        Span<byte> buf = this.scratchBuffer.Span.Slice(0, 4);
         BinaryPrimitives.WriteUInt32BigEndian(buf, (uint)chunkType);
         stream.Write(buf);
         BinaryPrimitives.WriteUInt32LittleEndian(buf, size);
@@ -151,7 +152,7 @@ internal abstract class BitWriterBase
     protected void WriteAlphaChunk(Stream stream, Span<byte> dataBytes, bool alphaDataIsCompressed)
     {
         uint size = (uint)dataBytes.Length + 1;
-        Span<byte> buf = this.scratchBuffer.AsSpan(0, 4);
+        Span<byte> buf = this.scratchBuffer.Span.Slice(0, 4);
         BinaryPrimitives.WriteUInt32BigEndian(buf, (uint)WebpChunkType.Alpha);
         stream.Write(buf);
         BinaryPrimitives.WriteUInt32LittleEndian(buf, size);
@@ -182,7 +183,7 @@ internal abstract class BitWriterBase
     {
         uint size = (uint)iccProfileBytes.Length;
 
-        Span<byte> buf = this.scratchBuffer.AsSpan(0, 4);
+        Span<byte> buf = this.scratchBuffer.Span.Slice(0, 4);
         BinaryPrimitives.WriteUInt32BigEndian(buf, (uint)WebpChunkType.Iccp);
         stream.Write(buf);
         BinaryPrimitives.WriteUInt32LittleEndian(buf, size);
@@ -245,7 +246,7 @@ internal abstract class BitWriterBase
             flags |= 32;
         }
 
-        Span<byte> buf = this.scratchBuffer.AsSpan(0, 4);
+        Span<byte> buf = this.scratchBuffer.Span.Slice(0, 4);
         stream.Write(WebpConstants.Vp8XMagicBytes);
         BinaryPrimitives.WriteUInt32LittleEndian(buf, WebpConstants.Vp8XChunkSize);
         stream.Write(buf);
@@ -256,4 +257,12 @@ internal abstract class BitWriterBase
         BinaryPrimitives.WriteUInt32LittleEndian(buf, height - 1);
         stream.Write(buf[..3]);
     }
+
+    private unsafe struct ScratchBuffer
+    {
+        private const int Size = 4;
+        private fixed byte scratch[Size];
+
+        public Span<byte> Span => MemoryMarshal.CreateSpan(ref this.scratch[0], Size);
+    }
 }

src/ImageSharp/Formats/Webp/BitWriter/Vp8LBitWriter.cs

@@ -14,11 +14,6 @@ namespace SixLabors.ImageSharp.Formats.Webp.BitWriter;
 /// </summary>
 internal class Vp8LBitWriter : BitWriterBase
 {
-    /// <summary>
-    /// A scratch buffer to reduce allocations.
-    /// </summary>
-    private readonly byte[] scratchBuffer = new byte[8];
-
     /// <summary>
     /// This is the minimum amount of size the memory buffer is guaranteed to grow when extra space is needed.
     /// </summary>
@@ -194,8 +189,9 @@ internal class Vp8LBitWriter : BitWriterBase
         stream.Write(WebpConstants.Vp8LMagicBytes);
 
         // Write Vp8 Header.
-        BinaryPrimitives.WriteUInt32LittleEndian(this.scratchBuffer, size);
-        stream.Write(this.scratchBuffer.AsSpan(0, 4));
+        Span<byte> scratchBuffer = stackalloc byte[8];
+        BinaryPrimitives.WriteUInt32LittleEndian(scratchBuffer, size);
+        stream.Write(scratchBuffer.Slice(0, 4));
         stream.WriteByte(WebpConstants.Vp8LHeaderMagicByte);
 
         // Write the encoded bytes of the image to the stream.
@@ -228,8 +224,9 @@ internal class Vp8LBitWriter : BitWriterBase
             this.BitWriterResize(extraSize);
         }
 
-        BinaryPrimitives.WriteUInt64LittleEndian(this.scratchBuffer, this.bits);
-        this.scratchBuffer.AsSpan(0, 4).CopyTo(this.Buffer.AsSpan(this.cur));
+        Span<byte> scratchBuffer = stackalloc byte[8];
+        BinaryPrimitives.WriteUInt64LittleEndian(scratchBuffer, this.bits);
+        scratchBuffer.Slice(0, 4).CopyTo(this.Buffer.AsSpan(this.cur));
 
         this.cur += WriterBytes;
         this.bits >>= WriterBits;

src/ImageSharp/Formats/Webp/Lossless/HistogramEncoder.cs

@@ -6,7 +6,7 @@ using System.Runtime.CompilerServices;
 
 namespace SixLabors.ImageSharp.Formats.Webp.Lossless;
 
-internal class HistogramEncoder
+internal static class HistogramEncoder
 {
     /// <summary>
     /// Number of partitions for the three dominant (literal, red and blue) symbol costs.
@@ -27,7 +27,7 @@ internal class HistogramEncoder
 
     private const ushort InvalidHistogramSymbol = ushort.MaxValue;
 
-    public static void GetHistoImageSymbols(int xSize, int ySize, Vp8LBackwardRefs refs, uint quality, int histoBits, int cacheBits, List<Vp8LHistogram> imageHisto, Vp8LHistogram tmpHisto, ushort[] histogramSymbols)
+    public static void GetHistoImageSymbols(int xSize, int ySize, Vp8LBackwardRefs refs, uint quality, int histoBits, int cacheBits, List<Vp8LHistogram> imageHisto, Vp8LHistogram tmpHisto, Span<ushort> histogramSymbols)
     {
         int histoXSize = histoBits > 0 ? LosslessUtils.SubSampleSize(xSize, histoBits) : 1;
         int histoYSize = histoBits > 0 ? LosslessUtils.SubSampleSize(ySize, histoBits) : 1;
@@ -148,7 +148,7 @@ internal class HistogramEncoder
         }
     }
 
-    private static int HistogramCopyAndAnalyze(List<Vp8LHistogram> origHistograms, List<Vp8LHistogram> histograms, ushort[] histogramSymbols)
+    private static int HistogramCopyAndAnalyze(List<Vp8LHistogram> origHistograms, List<Vp8LHistogram> histograms, Span<ushort> histogramSymbols)
     {
         var stats = new Vp8LStreaks();
         var bitsEntropy = new Vp8LBitEntropy();
@@ -171,20 +171,28 @@ internal class HistogramEncoder
             }
         }
 
-        int numUsed = histogramSymbols.Count(h => h != InvalidHistogramSymbol);
+        int numUsed = 0;
+        foreach (ushort h in histogramSymbols)
+        {
+            if (h != InvalidHistogramSymbol)
+            {
+                numUsed++;
+            }
+        }
+
         return numUsed;
     }
 
     private static void HistogramCombineEntropyBin(
         List<Vp8LHistogram> histograms,
-        ushort[] clusters,
+        Span<ushort> clusters,
         ushort[] clusterMappings,
         Vp8LHistogram curCombo,
         ushort[] binMap,
         int numBins,
         double combineCostFactor)
     {
-        var binInfo = new HistogramBinInfo[BinSize];
+        Span<HistogramBinInfo> binInfo = stackalloc HistogramBinInfo[BinSize];
         for (int idx = 0; idx < numBins; idx++)
         {
             binInfo[idx].First = -1;
@@ -258,7 +266,7 @@ internal class HistogramEncoder
     /// Given a Histogram set, the mapping of clusters 'clusterMapping' and the
     /// current assignment of the cells in 'symbols', merge the clusters and assign the smallest possible clusters values.
     /// </summary>
-    private static void OptimizeHistogramSymbols(ushort[] clusterMappings, int numClusters, ushort[] clusterMappingsTmp, ushort[] symbols)
+    private static void OptimizeHistogramSymbols(ushort[] clusterMappings, int numClusters, ushort[] clusterMappingsTmp, Span<ushort> symbols)
     {
         bool doContinue = true;
 
@@ -331,7 +339,7 @@ internal class HistogramEncoder
         int maxSize = 9;
 
         // Fill the initial mapping.
-        int[] mappings = new int[histograms.Count];
+        Span<int> mappings = histograms.Count <= 64 ? stackalloc int[histograms.Count] : new int[histograms.Count];
         for (int j = 0, iter = 0; iter < histograms.Count; iter++)
         {
             if (histograms[iter] == null)
@@ -388,9 +396,9 @@ internal class HistogramEncoder
             int bestIdx1 = histoPriorityList[0].Idx1;
             int bestIdx2 = histoPriorityList[0].Idx2;
 
-            int mappingIndex = Array.IndexOf(mappings, bestIdx2);
-            Span<int> src = mappings.AsSpan(mappingIndex + 1, numUsed - mappingIndex - 1);
-            Span<int> dst = mappings.AsSpan(mappingIndex);
+            int mappingIndex = mappings.IndexOf(bestIdx2);
+            Span<int> src = mappings.Slice(mappingIndex + 1, numUsed - mappingIndex - 1);
+            Span<int> dst = mappings.Slice(mappingIndex);
             src.CopyTo(dst);
 
             // Merge the histograms and remove bestIdx2 from the list.
@@ -528,7 +536,7 @@ internal class HistogramEncoder
         }
     }
 
-    private static void HistogramRemap(List<Vp8LHistogram> input, List<Vp8LHistogram> output, ushort[] symbols)
+    private static void HistogramRemap(List<Vp8LHistogram> input, List<Vp8LHistogram> output, Span<ushort> symbols)
     {
         int inSize = input.Count;
         int outSize = output.Count;

src/ImageSharp/Formats/Webp/Lossless/HuffmanUtils.cs

@@ -25,7 +25,7 @@ internal static class HuffmanUtils
         0x1, 0x9, 0x5, 0xd, 0x3, 0xb, 0x7, 0xf
     };
 
-    public static void CreateHuffmanTree(uint[] histogram, int treeDepthLimit, bool[] bufRle, HuffmanTree[] huffTree, HuffmanTreeCode huffCode)
+    public static void CreateHuffmanTree(uint[] histogram, int treeDepthLimit, bool[] bufRle, Span<HuffmanTree> huffTree, HuffmanTreeCode huffCode)
     {
         int numSymbols = huffCode.NumSymbols;
         bufRle.AsSpan().Clear();
@@ -159,7 +159,7 @@ internal static class HuffmanUtils
     /// <param name="histogramSize">The size of the histogram.</param>
     /// <param name="treeDepthLimit">The tree depth limit.</param>
     /// <param name="bitDepths">How many bits are used for the symbol.</param>
-    public static void GenerateOptimalTree(HuffmanTree[] tree, uint[] histogram, int histogramSize, int treeDepthLimit, byte[] bitDepths)
+    public static void GenerateOptimalTree(Span<HuffmanTree> tree, uint[] histogram, int histogramSize, int treeDepthLimit, byte[] bitDepths)
     {
         uint countMin;
         int treeSizeOrig = 0;
@@ -177,7 +177,7 @@ internal static class HuffmanUtils
             return;
         }
 
-        Span<HuffmanTree> treePool = tree.AsSpan(treeSizeOrig);
+        Span<HuffmanTree> treePool = tree.Slice(treeSizeOrig);
 
         // For block sizes with less than 64k symbols we never need to do a
         // second iteration of this loop.
@@ -202,14 +202,8 @@ internal static class HuffmanUtils
             }
 
             // Build the Huffman tree.
-#if NET5_0_OR_GREATER
-            Span<HuffmanTree> treeSlice = tree.AsSpan(0, treeSize);
+            Span<HuffmanTree> treeSlice = tree.Slice(0, treeSize);
             treeSlice.Sort(HuffmanTree.Compare);
-#else
-            HuffmanTree[] treeCopy = tree.AsSpan(0, treeSize).ToArray();
-            Array.Sort(treeCopy, HuffmanTree.Compare);
-            treeCopy.AsSpan().CopyTo(tree);
-#endif
 
             if (treeSize > 1)
             {
@@ -312,12 +306,12 @@ internal static class HuffmanUtils
         DebugGuard.MustBeGreaterThan(codeLengthsSize, 0, nameof(codeLengthsSize));
 
         // sorted[codeLengthsSize] is a pre-allocated array for sorting symbols by code length.
-        int[] sorted = new int[codeLengthsSize];
+        Span<int> sorted = codeLengthsSize <= 64 ? stackalloc int[codeLengthsSize] : new int[codeLengthsSize];
         int totalSize = 1 << rootBits; // total size root table + 2nd level table.
         int len; // current code length.
         int symbol; // symbol index in original or sorted table.
-        int[] counts = new int[WebpConstants.MaxAllowedCodeLength + 1]; // number of codes of each length.
-        int[] offsets = new int[WebpConstants.MaxAllowedCodeLength + 1]; // offsets in sorted table for each length.
+        Span<int> counts = stackalloc int[WebpConstants.MaxAllowedCodeLength + 1]; // number of codes of each length.
+        Span<int> offsets = stackalloc int[WebpConstants.MaxAllowedCodeLength + 1]; // offsets in sorted table for each length.
 
         // Build histogram of code lengths.
         for (symbol = 0; symbol < codeLengthsSize; ++symbol)
@@ -544,8 +538,8 @@ internal static class HuffmanUtils
     private static void ConvertBitDepthsToSymbols(HuffmanTreeCode tree)
     {
         // 0 bit-depth means that the symbol does not exist.
-        uint[] nextCode = new uint[WebpConstants.MaxAllowedCodeLength + 1];
-        int[] depthCount = new int[WebpConstants.MaxAllowedCodeLength + 1];
+        Span<uint> nextCode = stackalloc uint[WebpConstants.MaxAllowedCodeLength + 1];
+        Span<int> depthCount = stackalloc int[WebpConstants.MaxAllowedCodeLength + 1];
 
         int len = tree.NumSymbols;
         for (int i = 0; i < len; i++)
@@ -603,7 +597,7 @@ internal static class HuffmanUtils
     /// Returns the table width of the next 2nd level table. count is the histogram of bit lengths for the remaining symbols,
     /// len is the code length of the next processed symbol.
     /// </summary>
-    private static int NextTableBitSize(int[] count, int len, int rootBits)
+    private static int NextTableBitSize(ReadOnlySpan<int> count, int len, int rootBits)
     {
         int left = 1 << (len - rootBits);
         while (len < WebpConstants.MaxAllowedCodeLength)

src/ImageSharp/Formats/Webp/Lossless/PredictorEncoder.cs

@@ -57,11 +57,13 @@ internal static unsafe class PredictorEncoder
         Span<short> scratch = stackalloc short[8];
 
         // TODO: Can we optimize this?
-        int[][] histo = new int[4][];
-        for (int i = 0; i < 4; i++)
+        int[][] histo =
         {
-            histo[i] = new int[256];
-        }
+            new int[256],
+            new int[256],
+            new int[256],
+            new int[256]
+        };
 
         if (lowEffort)
         {
@@ -233,7 +235,7 @@ internal static unsafe class PredictorEncoder
         Span<byte> maxDiffs = MemoryMarshal.Cast<uint, byte>(currentRow[(width + 1)..]);
         float bestDiff = MaxDiffCost;
         int bestMode = 0;
-        uint[] residuals = new uint[1 << WebpConstants.MaxTransformBits];
+        Span<uint> residuals = stackalloc uint[1 << WebpConstants.MaxTransformBits];    // 256 bytes
         for (int i = 0; i < 4; i++)
         {
             histoArgb[i].AsSpan().Clear();
@@ -299,9 +301,7 @@ internal static unsafe class PredictorEncoder
 
             if (curDiff < bestDiff)
             {
-                int[][] tmp = histoArgb;
-                histoArgb = bestHisto;
-                bestHisto = tmp;
+                (bestHisto, histoArgb) = (histoArgb, bestHisto);
                 bestDiff = curDiff;
                 bestMode = mode;
             }

src/ImageSharp/Formats/Webp/Lossless/Vp8LEncoder.cs

@@ -23,7 +23,7 @@ internal class Vp8LEncoder : IDisposable
     /// <summary>
     /// Scratch buffer to reduce allocations.
     /// </summary>
-    private readonly int[] scratch = new int[256];
+    private ScratchBuffer scratch;  // mutable struct, don't make readonly
 
     private readonly int[][] histoArgb = { new int[256], new int[256], new int[256], new int[256] };
 
@@ -549,12 +549,8 @@ internal class Vp8LEncoder : IDisposable
         // bgra data with transformations applied.
         Span<uint> bgra = this.EncodedData.GetSpan();
         int histogramImageXySize = LosslessUtils.SubSampleSize(width, this.HistoBits) * LosslessUtils.SubSampleSize(height, this.HistoBits);
-        ushort[] histogramSymbols = new ushort[histogramImageXySize];
-        HuffmanTree[] huffTree = new HuffmanTree[3 * WebpConstants.CodeLengthCodes];
-        for (int i = 0; i < huffTree.Length; i++)
-        {
-            huffTree[i] = default;
-        }
+        Span<ushort> histogramSymbols = histogramImageXySize <= 64 ? stackalloc ushort[histogramImageXySize] : new ushort[histogramImageXySize];
+        Span<HuffmanTree> huffTree = stackalloc HuffmanTree[3 * WebpConstants.CodeLengthCodes];
 
         if (useCache)
         {
@@ -607,10 +603,6 @@ internal class Vp8LEncoder : IDisposable
             int histogramImageSize = histogramImage.Count;
             int bitArraySize = 5 * histogramImageSize;
             HuffmanTreeCode[] huffmanCodes = new HuffmanTreeCode[bitArraySize];
-            for (int i = 0; i < huffmanCodes.Length; i++)
-            {
-                huffmanCodes[i] = default;
-            }
 
             GetHuffBitLengthsAndCodes(histogramImage, huffmanCodes);
 
@@ -702,7 +694,7 @@ internal class Vp8LEncoder : IDisposable
     /// </summary>
     private void EncodePalette(bool lowEffort)
     {
-        Span<uint> tmpPalette = new uint[WebpConstants.MaxPaletteSize];
+        Span<uint> tmpPalette = stackalloc uint[WebpConstants.MaxPaletteSize];
         int paletteSize = this.PaletteSize;
         Span<uint> palette = this.Palette.Memory.Span;
         this.bitWriter.PutBits(WebpConstants.TransformPresent, 1);
@@ -763,7 +755,7 @@ internal class Vp8LEncoder : IDisposable
         int transformWidth = LosslessUtils.SubSampleSize(width, colorTransformBits);
         int transformHeight = LosslessUtils.SubSampleSize(height, colorTransformBits);
 
-        PredictorEncoder.ColorSpaceTransform(width, height, colorTransformBits, this.quality, this.EncodedData.GetSpan(), this.TransformData.GetSpan(), this.scratch);
+        PredictorEncoder.ColorSpaceTransform(width, height, colorTransformBits, this.quality, this.EncodedData.GetSpan(), this.TransformData.GetSpan(), this.scratch.Span);
 
         this.bitWriter.PutBits(WebpConstants.TransformPresent, 1);
         this.bitWriter.PutBits((uint)Vp8LTransformType.CrossColorTransform, 2);
@@ -778,16 +770,7 @@ internal class Vp8LEncoder : IDisposable
         ushort[] histogramSymbols = new ushort[1]; // Only one tree, one symbol.
 
         HuffmanTreeCode[] huffmanCodes = new HuffmanTreeCode[5];
-        for (int i = 0; i < huffmanCodes.Length; i++)
-        {
-            huffmanCodes[i] = default;
-        }
-
-        HuffmanTree[] huffTree = new HuffmanTree[3UL * WebpConstants.CodeLengthCodes];
-        for (int i = 0; i < huffTree.Length; i++)
-        {
-            huffTree[i] = default;
-        }
+        Span<HuffmanTree> huffTree = stackalloc HuffmanTree[3 * WebpConstants.CodeLengthCodes];
 
         // Calculate backward references from the image pixels.
         hashChain.Fill(bgra, quality, width, height, lowEffort);
@@ -847,10 +830,10 @@ internal class Vp8LEncoder : IDisposable
         this.StoreImageToBitMask(width, 0, refs, histogramSymbols, huffmanCodes);
     }
 
-    private void StoreHuffmanCode(HuffmanTree[] huffTree, HuffmanTreeToken[] tokens, HuffmanTreeCode huffmanCode)
+    private void StoreHuffmanCode(Span<HuffmanTree> huffTree, HuffmanTreeToken[] tokens, HuffmanTreeCode huffmanCode)
     {
         int count = 0;
-        Span<int> symbols = this.scratch.AsSpan(0, 2);
+        Span<int> symbols = this.scratch.Span.Slice(0, 2);
         symbols.Clear();
         const int maxBits = 8;
         const int maxSymbol = 1 << maxBits;
@@ -901,7 +884,7 @@ internal class Vp8LEncoder : IDisposable
         }
     }
 
-    private void StoreFullHuffmanCode(HuffmanTree[] huffTree, HuffmanTreeToken[] tokens, HuffmanTreeCode tree)
+    private void StoreFullHuffmanCode(Span<HuffmanTree> huffTree, HuffmanTreeToken[] tokens, HuffmanTreeCode tree)
     {
         int i;
         byte[] codeLengthBitDepth = new byte[WebpConstants.CodeLengthCodes];
@@ -1013,7 +996,7 @@ internal class Vp8LEncoder : IDisposable
         }
     }
 
-    private void StoreImageToBitMask(int width, int histoBits, Vp8LBackwardRefs backwardRefs, ushort[] histogramSymbols, HuffmanTreeCode[] huffmanCodes)
+    private void StoreImageToBitMask(int width, int histoBits, Vp8LBackwardRefs backwardRefs, Span<ushort> histogramSymbols, HuffmanTreeCode[] huffmanCodes)
     {
         int histoXSize = histoBits > 0 ? LosslessUtils.SubSampleSize(width, histoBits) : 1;
         int tileMask = histoBits == 0 ? 0 : -(1 << histoBits);
@@ -1143,8 +1126,8 @@ internal class Vp8LEncoder : IDisposable
             prevRow = currentRow;
         }
 
-        double[] entropyComp = new double[(int)HistoIx.HistoTotal];
-        double[] entropy = new double[(int)EntropyIx.NumEntropyIx];
+        Span<double> entropyComp = stackalloc double[(int)HistoIx.HistoTotal];
+        Span<double> entropy = stackalloc double[(int)EntropyIx.NumEntropyIx];
         int lastModeToAnalyze = usePalette ? (int)EntropyIx.Palette : (int)EntropyIx.SpatialSubGreen;
 
         // Let's add one zero to the predicted histograms. The zeros are removed
@@ -1647,11 +1630,7 @@ internal class Vp8LEncoder : IDisposable
 
         // Create Huffman trees.
         bool[] bufRle = new bool[maxNumSymbols];
-        HuffmanTree[] huffTree = new HuffmanTree[3 * maxNumSymbols];
-        for (int i = 0; i < huffTree.Length; i++)
-        {
-            huffTree[i] = default;
-        }
+        Span<HuffmanTree> huffTree = stackalloc HuffmanTree[3 * maxNumSymbols];
 
         for (int i = 0; i < histogramImage.Count; i++)
         {
@@ -1849,4 +1828,15 @@ internal class Vp8LEncoder : IDisposable
         this.TransformData.Dispose();
         this.HashChain.Dispose();
     }
+
+    /// <summary>
+    /// Scratch buffer to reduce allocations.
+    /// </summary>
+    private unsafe struct ScratchBuffer
+    {
+        private const int Size = 256;
+        private fixed int scratch[Size];
+
+        public Span<int> Span => MemoryMarshal.CreateSpan(ref this.scratch[0], Size);
+    }
 }

src/ImageSharp/Formats/Webp/Lossless/WebpLosslessDecoder.cs

@@ -498,10 +498,7 @@ internal sealed class WebpLosslessDecoder
     private int ReadHuffmanCode(int alphabetSize, int[] codeLengths, Span<HuffmanCode> table)
     {
         bool simpleCode = this.bitReader.ReadBit();
-        for (int i = 0; i < alphabetSize; i++)
-        {
-            codeLengths[i] = 0;
-        }
+        codeLengths.AsSpan(0, alphabetSize).Clear();
 
         if (simpleCode)
         {

src/ImageSharp/Formats/Webp/Lossy/QuantEnc.cs

@@ -121,7 +121,7 @@ internal static unsafe class QuantEnc
         var rdi4 = new Vp8ModeScore();
         var rdTmp = new Vp8ModeScore();
         var res = new Vp8Residual();
-        Span<short> tmpLevels = new short[16];
+        Span<short> tmpLevels = stackalloc short[16];
         do
         {
             const int numBlocks = 1;

src/ImageSharp/Formats/Webp/Lossy/Vp8EncIterator.cs

@@ -374,7 +374,7 @@ internal class Vp8EncIterator
         }
         else
         {
-            byte[] modes = new byte[16];  // DC4
+            Span<byte> modes = stackalloc byte[16];  // DC4
             this.SetIntra4Mode(modes);
         }
 
@@ -407,7 +407,7 @@ internal class Vp8EncIterator
 
     public int MbAnalyzeBestIntra4Mode(int bestAlpha)
     {
-        byte[] modes = new byte[16];
+        Span<byte> modes = stackalloc byte[16];
         const int maxMode = MaxIntra4Mode;
         Vp8Histogram totalHisto = new();
         int curHisto = 0;
@@ -494,13 +494,13 @@ internal class Vp8EncIterator
         this.CurrentMacroBlockInfo.MacroBlockType = Vp8MacroBlockType.I16X16;
     }
 
-    public void SetIntra4Mode(byte[] modes)
+    public void SetIntra4Mode(ReadOnlySpan<byte> modes)
     {
         int modesIdx = 0;
         int predIdx = this.PredIdx;
         for (int y = 4; y > 0; y--)
         {
-            modes.AsSpan(modesIdx, 4).CopyTo(this.Preds.AsSpan(predIdx));
+            modes.Slice(modesIdx, 4).CopyTo(this.Preds.AsSpan(predIdx));
             predIdx += this.predsWidth;
             modesIdx += 4;
         }

src/ImageSharp/Formats/Webp/Lossy/Vp8Encoder.cs

@@ -329,7 +329,7 @@ internal class Vp8Encoder : IDisposable
         int uvStride = (yStride + 1) >> 1;
 
         Vp8EncIterator it = new(this.YTop, this.UvTop, this.Nz, this.MbInfo, this.Preds, this.TopDerr, this.Mbw, this.Mbh);
-        int[] alphas = new int[WebpConstants.MaxAlpha + 1];
+        Span<int> alphas = stackalloc int[WebpConstants.MaxAlpha + 1];
         this.alpha = this.MacroBlockAnalysis(width, height, it, y, u, v, yStride, uvStride, alphas, out this.uvAlpha);
         int totalMb = this.Mbw * this.Mbw;
         this.alpha /= totalMb;
@@ -625,15 +625,15 @@ internal class Vp8Encoder : IDisposable
     }
 
     // Simplified k-Means, to assign Nb segments based on alpha-histogram.
-    private void AssignSegments(int[] alphas)
+    private void AssignSegments(ReadOnlySpan<int> alphas)
     {
         int nb = this.SegmentHeader.NumSegments < NumMbSegments ? this.SegmentHeader.NumSegments : NumMbSegments;
-        int[] centers = new int[NumMbSegments];
+        Span<int> centers = stackalloc int[NumMbSegments];
         int weightedAverage = 0;
-        int[] map = new int[WebpConstants.MaxAlpha + 1];
+        Span<int> map = stackalloc int[WebpConstants.MaxAlpha + 1];
         int n, k;
-        int[] accum = new int[NumMbSegments];
-        int[] distAccum = new int[NumMbSegments];
+        Span<int> accum = stackalloc int[NumMbSegments];
+        Span<int> distAccum = stackalloc int[NumMbSegments];
 
         // Bracket the input.
         for (n = 0; n <= WebpConstants.MaxAlpha && alphas[n] == 0; ++n)
@@ -719,7 +719,7 @@ internal class Vp8Encoder : IDisposable
         this.SetSegmentAlphas(centers, weightedAverage);
     }
 
-    private void SetSegmentAlphas(int[] centers, int mid)
+    private void SetSegmentAlphas(ReadOnlySpan<int> centers, int mid)
     {
         int nb = this.SegmentHeader.NumSegments;
         Vp8SegmentInfo[] dqm = this.SegmentInfos;
@@ -840,7 +840,7 @@ internal class Vp8Encoder : IDisposable
 
     private void SetSegmentProbas()
     {
-        int[] p = new int[NumMbSegments];
+        Span<int> p = stackalloc int[NumMbSegments];
         int n;
 
         for (n = 0; n < this.Mbw * this.Mbh; ++n)
@@ -931,7 +931,7 @@ internal class Vp8Encoder : IDisposable
         }
     }
 
-    private int MacroBlockAnalysis(int width, int height, Vp8EncIterator it, Span<byte> y, Span<byte> u, Span<byte> v, int yStride, int uvStride, int[] alphas, out int uvAlpha)
+    private int MacroBlockAnalysis(int width, int height, Vp8EncIterator it, Span<byte> y, Span<byte> u, Span<byte> v, int yStride, int uvStride, Span<int> alphas, out int uvAlpha)
     {
         int alpha = 0;
         uvAlpha = 0;
@@ -952,7 +952,7 @@ internal class Vp8Encoder : IDisposable
         return alpha;
     }
 
-    private int MbAnalyze(Vp8EncIterator it, int[] alphas, out int bestUvAlpha)
+    private int MbAnalyze(Vp8EncIterator it, Span<int> alphas, out int bestUvAlpha)
     {
         it.SetIntra16Mode(0);    // default: Intra16, DC_PRED
         it.SetSkip(false);       // not skipped.

src/ImageSharp/Formats/Webp/Lossy/Vp8Histogram.cs

@@ -10,12 +10,6 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossy;
 
 internal sealed class Vp8Histogram
 {
-    private readonly int[] scratch = new int[16];
-
-    private readonly short[] output = new short[16];
-
-    private readonly int[] distribution = new int[MaxCoeffThresh + 1];
-
     /// <summary>
     /// Size of histogram used by CollectHistogram.
     /// </summary>
@@ -47,17 +41,20 @@ internal sealed class Vp8Histogram
 
     public void CollectHistogram(Span<byte> reference, Span<byte> pred, int startBlock, int endBlock)
     {
+        Span<int> scratch = stackalloc int[16];
+        Span<short> output = stackalloc short[16];
+        Span<int> distribution = stackalloc int[MaxCoeffThresh + 1];
+
         int j;
-        this.distribution.AsSpan().Clear();
         for (j = startBlock; j < endBlock; j++)
         {
-            Vp8Encoding.FTransform(reference[WebpLookupTables.Vp8DspScan[j]..], pred[WebpLookupTables.Vp8DspScan[j]..], this.output, this.scratch);
+            Vp8Encoding.FTransform(reference[WebpLookupTables.Vp8DspScan[j]..], pred[WebpLookupTables.Vp8DspScan[j]..], output, scratch);
 
             // Convert coefficients to bin.
             if (Avx2.IsSupported)
             {
                 // Load.
-                ref short outputRef = ref MemoryMarshal.GetReference<short>(this.output);
+                ref short outputRef = ref MemoryMarshal.GetReference(output);
                 Vector256<byte> out0 = Unsafe.As<short, Vector256<byte>>(ref outputRef);
 
                 // v = abs(out) >> 3
@@ -73,21 +70,21 @@ internal sealed class Vp8Histogram
                 // Convert coefficients to bin.
                 for (int k = 0; k < 16; ++k)
                 {
-                    ++this.distribution[this.output[k]];
+                    ++distribution[output[k]];
                 }
             }
             else
             {
                 for (int k = 0; k < 16; ++k)
                 {
-                    int v = Math.Abs(this.output[k]) >> 3;
+                    int v = Math.Abs(output[k]) >> 3;
                     int clippedValue = ClipMax(v, MaxCoeffThresh);
-                    ++this.distribution[clippedValue];
+                    ++distribution[clippedValue];
                 }
             }
         }
 
-        this.SetHistogramData(this.distribution);
+        this.SetHistogramData(distribution);
     }
 
     public void Merge(Vp8Histogram other)
@@ -103,7 +100,7 @@ internal sealed class Vp8Histogram
         }
     }
 
-    private void SetHistogramData(int[] distribution)
+    private void SetHistogramData(ReadOnlySpan<int> distribution)
     {
         int maxValue = 0;
         int lastNonZero = 1;

src/ImageSharp/Formats/Webp/Lossy/Vp8Residual.cs

@@ -15,10 +15,6 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossy;
 /// </summary>
 internal class Vp8Residual
 {
-    private readonly byte[] scratch = new byte[32];
-
-    private readonly ushort[] scratchUShort = new ushort[16];
-
     public int First { get; set; }
 
     public int Last { get; set; }
@@ -162,9 +158,10 @@ internal class Vp8Residual
 
         if (Avx2.IsSupported)
         {
-            Span<byte> ctxs = this.scratch.AsSpan(0, 16);
-            Span<byte> levels = this.scratch.AsSpan(16, 16);
-            Span<ushort> absLevels = this.scratchUShort.AsSpan();
+            Span<byte> scratch = stackalloc byte[32];
+            Span<byte> ctxs = scratch.Slice(0, 16);
+            Span<byte> levels = scratch.Slice(16);
+            Span<ushort> absLevels = stackalloc ushort[16];
 
             // Precompute clamped levels and contexts, packed to 8b.
             ref short outputRef = ref MemoryMarshal.GetReference<short>(this.Coeffs);

src/ImageSharp/Formats/Webp/Lossy/WebpLossyDecoder.cs

@@ -34,16 +34,6 @@ internal sealed class WebpLossyDecoder
     /// </summary>
     private readonly Configuration configuration;
 
-    /// <summary>
-    /// Scratch buffer to reduce allocations.
-    /// </summary>
-    private readonly int[] scratch = new int[16];
-
-    /// <summary>
-    /// Another scratch buffer to reduce allocations.
-    /// </summary>
-    private readonly byte[] scratchBytes = new byte[4];
-
     /// <summary>
     /// Initializes a new instance of the <see cref="WebpLossyDecoder"/> class.
     /// </summary>
@@ -371,6 +361,9 @@ internal sealed class WebpLossyDecoder
             }
         }
 
+        Span<int> scratch = stackalloc int[16];
+        Span<byte> scratchBytes = stackalloc byte[4];
+
         // Reconstruct one row.
         for (int mbx = 0; mbx < dec.MbWidth; mbx++)
         {
@@ -448,7 +441,7 @@ internal sealed class WebpLossyDecoder
                             LossyUtils.TM4(dst, yuv, offset);
                             break;
                         case 2:
-                            LossyUtils.VE4(dst, yuv, offset, this.scratchBytes);
+                            LossyUtils.VE4(dst, yuv, offset, scratchBytes);
                             break;
                         case 3:
                             LossyUtils.HE4(dst, yuv, offset);
@@ -473,7 +466,7 @@ internal sealed class WebpLossyDecoder
                             break;
                     }
 
-                    DoTransform(bits, coeffs.AsSpan(n * 16), dst, this.scratch);
+                    DoTransform(bits, coeffs.AsSpan(n * 16), dst, scratch);
                 }
             }
             else
@@ -508,7 +501,7 @@ internal sealed class WebpLossyDecoder
                 {
                     for (int n = 0; n < 16; ++n, bits <<= 2)
                     {
-                        DoTransform(bits, coeffs.AsSpan(n * 16), yDst[WebpConstants.Scan[n]..], this.scratch);
+                        DoTransform(bits, coeffs.AsSpan(n * 16), yDst[WebpConstants.Scan[n]..], scratch);
                     }
                 }
             }
@@ -547,8 +540,8 @@ internal sealed class WebpLossyDecoder
                     break;
             }
 
-            DoUVTransform(bitsUv, coeffs.AsSpan(16 * 16), uDst, this.scratch);
-            DoUVTransform(bitsUv >> 8, coeffs.AsSpan(20 * 16), vDst, this.scratch);
+            DoUVTransform(bitsUv, coeffs.AsSpan(16 * 16), uDst, scratch);
+            DoUVTransform(bitsUv >> 8, coeffs.AsSpan(20 * 16), vDst, scratch);
 
             // Stash away top samples for next block.
             if (mby < dec.MbHeight - 1)
@@ -875,14 +868,14 @@ internal sealed class WebpLossyDecoder
         else
         {
             // Parse DC
-            short[] dc = new short[16];
+            Span<short> dc = stackalloc short[16];
             int ctx = (int)(mb.NoneZeroDcCoeffs + leftMb.NoneZeroDcCoeffs);
             int nz = GetCoeffs(br, bands[1], ctx, q.Y2Mat, 0, dc);
             mb.NoneZeroDcCoeffs = leftMb.NoneZeroDcCoeffs = (uint)(nz > 0 ? 1 : 0);
             if (nz > 1)
             {
                 // More than just the DC -> perform the full transform.
-                LossyUtils.TransformWht(dc, dst, this.scratch);
+                LossyUtils.TransformWht(dc, dst, stackalloc int[16]);
             }
             else
             {

src/ImageSharp/Formats/Webp/WebpAnimationDecoder.cs

@@ -17,11 +17,6 @@ namespace SixLabors.ImageSharp.Formats.Webp;
 /// </summary>
 internal class WebpAnimationDecoder : IDisposable
 {
-    /// <summary>
-    /// Reusable buffer.
-    /// </summary>
-    private readonly byte[] buffer = new byte[4];
-
     /// <summary>
     /// Used for allocating memory during the decoding operations.
     /// </summary>
@@ -89,11 +84,12 @@ internal class WebpAnimationDecoder : IDisposable
         this.webpMetadata = this.metadata.GetWebpMetadata();
         this.webpMetadata.AnimationLoopCount = features.AnimationLoopCount;
 
+        Span<byte> buffer = stackalloc byte[4];
         uint frameCount = 0;
         int remainingBytes = (int)completeDataSize;
         while (remainingBytes > 0)
         {
-            WebpChunkType chunkType = WebpChunkParsingUtils.ReadChunkType(stream, this.buffer);
+            WebpChunkType chunkType = WebpChunkParsingUtils.ReadChunkType(stream, buffer);
             remainingBytes -= 4;
             switch (chunkType)
             {
@@ -103,7 +99,7 @@ internal class WebpAnimationDecoder : IDisposable
                     break;
                 case WebpChunkType.Xmp:
                 case WebpChunkType.Exif:
-                    WebpChunkParsingUtils.ParseOptionalChunks(stream, chunkType, image!.Metadata, false, this.buffer);
+                    WebpChunkParsingUtils.ParseOptionalChunks(stream, chunkType, image!.Metadata, false, buffer);
                     break;
                 default:
                     WebpThrowHelper.ThrowImageFormatException("Read unexpected webp chunk data");
@@ -134,15 +130,16 @@ internal class WebpAnimationDecoder : IDisposable
     {
         AnimationFrameData frameData = this.ReadFrameHeader(stream);
         long streamStartPosition = stream.Position;
+        Span<byte> buffer = stackalloc byte[4];
 
-        WebpChunkType chunkType = WebpChunkParsingUtils.ReadChunkType(stream, this.buffer);
+        WebpChunkType chunkType = WebpChunkParsingUtils.ReadChunkType(stream, buffer);
         bool hasAlpha = false;
         byte alphaChunkHeader = 0;
         if (chunkType is WebpChunkType.Alpha)
         {
             alphaChunkHeader = this.ReadAlphaData(stream);
             hasAlpha = true;
-            chunkType = WebpChunkParsingUtils.ReadChunkType(stream, this.buffer);
+            chunkType = WebpChunkParsingUtils.ReadChunkType(stream, buffer);
         }
 
         WebpImageInfo? webpInfo = null;
@@ -150,12 +147,12 @@ internal class WebpAnimationDecoder : IDisposable
         switch (chunkType)
         {
             case WebpChunkType.Vp8:
-                webpInfo = WebpChunkParsingUtils.ReadVp8Header(this.memoryAllocator, stream, this.buffer, features);
+                webpInfo = WebpChunkParsingUtils.ReadVp8Header(this.memoryAllocator, stream, buffer, features);
                 features.Alpha = hasAlpha;
                 features.AlphaChunkHeader = alphaChunkHeader;
                 break;
             case WebpChunkType.Vp8L:
-                webpInfo = WebpChunkParsingUtils.ReadVp8LHeader(this.memoryAllocator, stream, this.buffer, features);
+                webpInfo = WebpChunkParsingUtils.ReadVp8LHeader(this.memoryAllocator, stream, buffer, features);
                 break;
             default:
                 WebpThrowHelper.ThrowImageFormatException("Read unexpected chunk type, should be VP8 or VP8L");
@@ -226,7 +223,7 @@ internal class WebpAnimationDecoder : IDisposable
     {
         this.alphaData?.Dispose();
 
-        uint alphaChunkSize = WebpChunkParsingUtils.ReadChunkSize(stream, this.buffer);
+        uint alphaChunkSize = WebpChunkParsingUtils.ReadChunkSize(stream, stackalloc byte[4]);
         int alphaDataSize = (int)(alphaChunkSize - 1);
         this.alphaData = this.memoryAllocator.Allocate<byte>(alphaDataSize);
 
@@ -353,24 +350,26 @@ internal class WebpAnimationDecoder : IDisposable
     /// <returns>Animation frame data.</returns>
     private AnimationFrameData ReadFrameHeader(BufferedReadStream stream)
     {
+        Span<byte> buffer = stackalloc byte[4];
+
         AnimationFrameData data = new()
         {
-            DataSize = WebpChunkParsingUtils.ReadChunkSize(stream, this.buffer),
+            DataSize = WebpChunkParsingUtils.ReadChunkSize(stream, buffer),
 
             // 3 bytes for the X coordinate of the upper left corner of the frame.
-            X = WebpChunkParsingUtils.ReadUnsignedInt24Bit(stream, this.buffer),
+            X = WebpChunkParsingUtils.ReadUnsignedInt24Bit(stream, buffer),
 
             // 3 bytes for the Y coordinate of the upper left corner of the frame.
-            Y = WebpChunkParsingUtils.ReadUnsignedInt24Bit(stream, this.buffer),
+            Y = WebpChunkParsingUtils.ReadUnsignedInt24Bit(stream, buffer),
 
             // Frame width Minus One.
-            Width = WebpChunkParsingUtils.ReadUnsignedInt24Bit(stream, this.buffer) + 1,
+            Width = WebpChunkParsingUtils.ReadUnsignedInt24Bit(stream, buffer) + 1,
 
             // Frame height Minus One.
-            Height = WebpChunkParsingUtils.ReadUnsignedInt24Bit(stream, this.buffer) + 1,
+            Height = WebpChunkParsingUtils.ReadUnsignedInt24Bit(stream, buffer) + 1,
 
             // Frame duration.
-            Duration = WebpChunkParsingUtils.ReadUnsignedInt24Bit(stream, this.buffer)
+            Duration = WebpChunkParsingUtils.ReadUnsignedInt24Bit(stream, buffer)
         };
 
         byte flags = (byte)stream.ReadByte();

src/ImageSharp/Formats/Webp/WebpChunkParsingUtils.cs

@@ -18,7 +18,7 @@ internal static class WebpChunkParsingUtils
     /// Reads the header of a lossy webp image.
     /// </summary>
     /// <returns>Information about this webp image.</returns>
-    public static WebpImageInfo ReadVp8Header(MemoryAllocator memoryAllocator, BufferedReadStream stream, byte[] buffer, WebpFeatures features)
+    public static WebpImageInfo ReadVp8Header(MemoryAllocator memoryAllocator, BufferedReadStream stream, Span<byte> buffer, WebpFeatures features)
     {
         // VP8 data size (not including this 4 bytes).
         int bytesRead = stream.Read(buffer, 0, 4);
@@ -77,7 +77,7 @@ internal static class WebpChunkParsingUtils
             WebpThrowHelper.ThrowInvalidImageContentException("Not enough data to read the VP8 magic bytes");
         }
 
-        if (!buffer.AsSpan(0, 3).SequenceEqual(WebpConstants.Vp8HeaderMagicBytes))
+        if (!buffer.Slice(0, 3).SequenceEqual(WebpConstants.Vp8HeaderMagicBytes))
         {
             WebpThrowHelper.ThrowImageFormatException("VP8 magic bytes not found");
         }
@@ -91,7 +91,7 @@ internal static class WebpChunkParsingUtils
         uint tmp = BinaryPrimitives.ReadUInt16LittleEndian(buffer);
         uint width = tmp & 0x3fff;
         sbyte xScale = (sbyte)(tmp >> 6);
-        tmp = BinaryPrimitives.ReadUInt16LittleEndian(buffer.AsSpan(2));
+        tmp = BinaryPrimitives.ReadUInt16LittleEndian(buffer.Slice(2));
         uint height = tmp & 0x3fff;
         sbyte yScale = (sbyte)(tmp >> 6);
         remaining -= 7;
@@ -140,7 +140,7 @@ internal static class WebpChunkParsingUtils
     /// Reads the header of a lossless webp image.
     /// </summary>
     /// <returns>Information about this image.</returns>
-    public static WebpImageInfo ReadVp8LHeader(MemoryAllocator memoryAllocator, BufferedReadStream stream, byte[] buffer, WebpFeatures features)
+    public static WebpImageInfo ReadVp8LHeader(MemoryAllocator memoryAllocator, BufferedReadStream stream, Span<byte> buffer, WebpFeatures features)
     {
         // VP8 data size.
         uint imageDataSize = ReadChunkSize(stream, buffer);
@@ -195,7 +195,7 @@ internal static class WebpChunkParsingUtils
     /// After the image header, image data will follow. After that optional image metadata chunks (EXIF and XMP) can follow.
     /// </summary>
     /// <returns>Information about this webp image.</returns>
-    public static WebpImageInfo ReadVp8XHeader(BufferedReadStream stream, byte[] buffer, WebpFeatures features)
+    public static WebpImageInfo ReadVp8XHeader(BufferedReadStream stream, Span<byte> buffer, WebpFeatures features)
     {
         uint fileSize = ReadChunkSize(stream, buffer);
 
@@ -253,7 +253,7 @@ internal static class WebpChunkParsingUtils
     /// <param name="stream">The stream to read from.</param>
     /// <param name="buffer">The buffer to store the read data into.</param>
     /// <returns>A unsigned 24 bit integer.</returns>
-    public static uint ReadUnsignedInt24Bit(BufferedReadStream stream, byte[] buffer)
+    public static uint ReadUnsignedInt24Bit(BufferedReadStream stream, Span<byte> buffer)
     {
         if (stream.Read(buffer, 0, 3) == 3)
         {
@@ -271,9 +271,11 @@ internal static class WebpChunkParsingUtils
     /// <param name="stream">The stream to read the data from.</param>
     /// <param name="buffer">Buffer to store the data read from the stream.</param>
     /// <returns>The chunk size in bytes.</returns>
-    public static uint ReadChunkSize(BufferedReadStream stream, byte[] buffer)
+    public static uint ReadChunkSize(BufferedReadStream stream, Span<byte> buffer)
     {
-        if (stream.Read(buffer, 0, 4) == 4)
+        DebugGuard.IsTrue(buffer.Length == 4, "buffer has wrong length");
+
+        if (stream.Read(buffer) == 4)
         {
             uint chunkSize = BinaryPrimitives.ReadUInt32LittleEndian(buffer);
             return (chunkSize % 2 == 0) ? chunkSize : chunkSize + 1;
@@ -290,9 +292,11 @@ internal static class WebpChunkParsingUtils
     /// <exception cref="ImageFormatException">
     /// Thrown if the input stream is not valid.
     /// </exception>
-    public static WebpChunkType ReadChunkType(BufferedReadStream stream, byte[] buffer)
+    public static WebpChunkType ReadChunkType(BufferedReadStream stream, Span<byte> buffer)
     {
-        if (stream.Read(buffer, 0, 4) == 4)
+        DebugGuard.IsTrue(buffer.Length == 4, "buffer has wrong length");
+
+        if (stream.Read(buffer) == 4)
         {
             var chunkType = (WebpChunkType)BinaryPrimitives.ReadUInt32BigEndian(buffer);
             return chunkType;
@@ -306,7 +310,7 @@ internal static class WebpChunkParsingUtils
     /// If there are more such chunks, readers MAY ignore all except the first one.
     /// Also, a file may possibly contain both 'EXIF' and 'XMP ' chunks.
     /// </summary>
-    public static void ParseOptionalChunks(BufferedReadStream stream, WebpChunkType chunkType, ImageMetadata metadata, bool ignoreMetaData, byte[] buffer)
+    public static void ParseOptionalChunks(BufferedReadStream stream, WebpChunkType chunkType, ImageMetadata metadata, bool ignoreMetaData, Span<byte> buffer)
     {
         long streamLength = stream.Length;
         while (stream.Position < streamLength)

src/ImageSharp/Formats/Webp/WebpDecoderCore.cs

@@ -18,11 +18,6 @@ namespace SixLabors.ImageSharp.Formats.Webp;
 /// </summary>
 internal sealed class WebpDecoderCore : IImageDecoderInternals, IDisposable
 {
-    /// <summary>
-    /// Reusable buffer.
-    /// </summary>
-    private readonly byte[] buffer = new byte[4];
-
     /// <summary>
     /// General configuration options.
     /// </summary>
@@ -80,8 +75,9 @@ internal sealed class WebpDecoderCore : IImageDecoderInternals, IDisposable
         try
         {
             ImageMetadata metadata = new();
+            Span<byte> buffer = stackalloc byte[4];
 
-            uint fileSize = this.ReadImageHeader(stream);
+            uint fileSize = ReadImageHeader(stream, buffer);
 
             using (this.webImageInfo = this.ReadVp8Info(stream, metadata))
             {
@@ -112,7 +108,7 @@ internal sealed class WebpDecoderCore : IImageDecoderInternals, IDisposable
                 // There can be optional chunks after the image data, like EXIF and XMP.
                 if (this.webImageInfo.Features != null)
                 {
-                    this.ParseOptionalChunks(stream, metadata, this.webImageInfo.Features);
+                    this.ParseOptionalChunks(stream, metadata, this.webImageInfo.Features, buffer);
                 }
 
                 return image;
@@ -128,7 +124,7 @@ internal sealed class WebpDecoderCore : IImageDecoderInternals, IDisposable
     /// <inheritdoc />
     public ImageInfo Identify(BufferedReadStream stream, CancellationToken cancellationToken)
     {
-        this.ReadImageHeader(stream);
+        ReadImageHeader(stream, stackalloc byte[4]);
 
         ImageMetadata metadata = new();
         using (this.webImageInfo = this.ReadVp8Info(stream, metadata, true))
@@ -144,8 +140,9 @@ internal sealed class WebpDecoderCore : IImageDecoderInternals, IDisposable
     /// Reads and skips over the image header.
     /// </summary>
     /// <param name="stream">The stream to decode from.</param>
+    /// <param name="buffer">Temporary buffer.</param>
     /// <returns>The file size in bytes.</returns>
-    private uint ReadImageHeader(BufferedReadStream stream)
+    private static uint ReadImageHeader(BufferedReadStream stream, Span<byte> buffer)
     {
         // Skip FourCC header, we already know its a RIFF file at this point.
         stream.Skip(4);
@@ -153,7 +150,7 @@ internal sealed class WebpDecoderCore : IImageDecoderInternals, IDisposable
         // Read file size.
         // The size of the file in bytes starting at offset 8.
         // The file size in the header is the total size of the chunks that follow plus 4 bytes for the ‘WEBP’ FourCC.
-        uint fileSize = WebpChunkParsingUtils.ReadChunkSize(stream, this.buffer);
+        uint fileSize = WebpChunkParsingUtils.ReadChunkSize(stream, buffer);
 
         // Skip 'WEBP' from the header.
         stream.Skip(4);
@@ -172,35 +169,36 @@ internal sealed class WebpDecoderCore : IImageDecoderInternals, IDisposable
     {
         WebpMetadata webpMetadata = metadata.GetFormatMetadata(WebpFormat.Instance);
 
-        WebpChunkType chunkType = WebpChunkParsingUtils.ReadChunkType(stream, this.buffer);
+        Span<byte> buffer = stackalloc byte[4];
+        WebpChunkType chunkType = WebpChunkParsingUtils.ReadChunkType(stream, buffer);
 
         WebpFeatures features = new();
         switch (chunkType)
         {
             case WebpChunkType.Vp8:
                 webpMetadata.FileFormat = WebpFileFormatType.Lossy;
-                return WebpChunkParsingUtils.ReadVp8Header(this.memoryAllocator, stream, this.buffer, features);
+                return WebpChunkParsingUtils.ReadVp8Header(this.memoryAllocator, stream, buffer, features);
             case WebpChunkType.Vp8L:
                 webpMetadata.FileFormat = WebpFileFormatType.Lossless;
-                return WebpChunkParsingUtils.ReadVp8LHeader(this.memoryAllocator, stream, this.buffer, features);
+                return WebpChunkParsingUtils.ReadVp8LHeader(this.memoryAllocator, stream, buffer, features);
             case WebpChunkType.Vp8X:
-                WebpImageInfo webpInfos = WebpChunkParsingUtils.ReadVp8XHeader(stream, this.buffer, features);
+                WebpImageInfo webpInfos = WebpChunkParsingUtils.ReadVp8XHeader(stream, buffer, features);
                 while (stream.Position < stream.Length)
                 {
-                    chunkType = WebpChunkParsingUtils.ReadChunkType(stream, this.buffer);
+                    chunkType = WebpChunkParsingUtils.ReadChunkType(stream, buffer);
                     if (chunkType == WebpChunkType.Vp8)
                     {
                         webpMetadata.FileFormat = WebpFileFormatType.Lossy;
-                        webpInfos = WebpChunkParsingUtils.ReadVp8Header(this.memoryAllocator, stream, this.buffer, features);
+                        webpInfos = WebpChunkParsingUtils.ReadVp8Header(this.memoryAllocator, stream, buffer, features);
                     }
                     else if (chunkType == WebpChunkType.Vp8L)
                     {
                         webpMetadata.FileFormat = WebpFileFormatType.Lossless;
-                        webpInfos = WebpChunkParsingUtils.ReadVp8LHeader(this.memoryAllocator, stream, this.buffer, features);
+                        webpInfos = WebpChunkParsingUtils.ReadVp8LHeader(this.memoryAllocator, stream, buffer, features);
                     }
                     else if (WebpChunkParsingUtils.IsOptionalVp8XChunk(chunkType))
                     {
-                        bool isAnimationChunk = this.ParseOptionalExtendedChunks(stream, metadata, chunkType, features, ignoreAlpha);
+                        bool isAnimationChunk = this.ParseOptionalExtendedChunks(stream, metadata, chunkType, features, ignoreAlpha, buffer);
                         if (isAnimationChunk)
                         {
                             return webpInfos;
@@ -209,7 +207,7 @@ internal sealed class WebpDecoderCore : IImageDecoderInternals, IDisposable
                     else
                     {
                         // Ignore unknown chunks.
-                        uint chunkSize = this.ReadChunkSize(stream);
+                        uint chunkSize = ReadChunkSize(stream, buffer);
                         stream.Skip((int)chunkSize);
                     }
                 }
@@ -230,34 +228,36 @@ internal sealed class WebpDecoderCore : IImageDecoderInternals, IDisposable
     /// <param name="chunkType">The chunk type.</param>
     /// <param name="features">The webp image features.</param>
     /// <param name="ignoreAlpha">For identify, the alpha data should not be read.</param>
+    /// <param name="buffer">Temporary buffer.</param>
     /// <returns>true, if its a alpha chunk.</returns>
     private bool ParseOptionalExtendedChunks(
         BufferedReadStream stream,
         ImageMetadata metadata,
         WebpChunkType chunkType,
         WebpFeatures features,
-        bool ignoreAlpha)
+        bool ignoreAlpha,
+        Span<byte> buffer)
     {
         switch (chunkType)
         {
             case WebpChunkType.Iccp:
-                this.ReadIccProfile(stream, metadata);
+                this.ReadIccProfile(stream, metadata, buffer);
                 break;
 
             case WebpChunkType.Exif:
-                this.ReadExifProfile(stream, metadata);
+                this.ReadExifProfile(stream, metadata, buffer);
                 break;
 
             case WebpChunkType.Xmp:
-                this.ReadXmpProfile(stream, metadata);
+                this.ReadXmpProfile(stream, metadata, buffer);
                 break;
 
             case WebpChunkType.AnimationParameter:
-                this.ReadAnimationParameters(stream, features);
+                ReadAnimationParameters(stream, features, buffer);
                 return true;
 
             case WebpChunkType.Alpha:
-                this.ReadAlphaData(stream, features, ignoreAlpha);
+                this.ReadAlphaData(stream, features, ignoreAlpha, buffer);
                 break;
             default:
                 WebpThrowHelper.ThrowImageFormatException("Unexpected chunk followed VP8X header");
@@ -273,7 +273,8 @@ internal sealed class WebpDecoderCore : IImageDecoderInternals, IDisposable
     /// <param name="stream">The stream to decode from.</param>
     /// <param name="metadata">The image metadata.</param>
     /// <param name="features">The webp features.</param>
-    private void ParseOptionalChunks(BufferedReadStream stream, ImageMetadata metadata, WebpFeatures features)
+    /// <param name="buffer">Temporary buffer.</param>
+    private void ParseOptionalChunks(BufferedReadStream stream, ImageMetadata metadata, WebpFeatures features, Span<byte> buffer)
     {
         if (this.skipMetadata || (!features.ExifProfile && !features.XmpMetaData))
         {
@@ -284,19 +285,19 @@ internal sealed class WebpDecoderCore : IImageDecoderInternals, IDisposable
         while (stream.Position < streamLength)
         {
             // Read chunk header.
-            WebpChunkType chunkType = this.ReadChunkType(stream);
+            WebpChunkType chunkType = ReadChunkType(stream, buffer);
             if (chunkType == WebpChunkType.Exif && metadata.ExifProfile == null)
             {
-                this.ReadExifProfile(stream, metadata);
+                this.ReadExifProfile(stream, metadata, buffer);
             }
             else if (chunkType == WebpChunkType.Xmp && metadata.XmpProfile == null)
             {
-                this.ReadXmpProfile(stream, metadata);
+                this.ReadXmpProfile(stream, metadata, buffer);
             }
             else
             {
                 // Skip duplicate XMP or EXIF chunk.
-                uint chunkLength = this.ReadChunkSize(stream);
+                uint chunkLength = ReadChunkSize(stream, buffer);
                 stream.Skip((int)chunkLength);
             }
         }
@@ -307,9 +308,10 @@ internal sealed class WebpDecoderCore : IImageDecoderInternals, IDisposable
     /// </summary>
     /// <param name="stream">The stream to decode from.</param>
     /// <param name="metadata">The image metadata.</param>
-    private void ReadExifProfile(BufferedReadStream stream, ImageMetadata metadata)
+    /// <param name="buffer">Temporary buffer.</param>
+    private void ReadExifProfile(BufferedReadStream stream, ImageMetadata metadata, Span<byte> buffer)
     {
-        uint exifChunkSize = this.ReadChunkSize(stream);
+        uint exifChunkSize = ReadChunkSize(stream, buffer);
         if (this.skipMetadata)
         {
             stream.Skip((int)exifChunkSize);
@@ -333,9 +335,10 @@ internal sealed class WebpDecoderCore : IImageDecoderInternals, IDisposable
     /// </summary>
     /// <param name="stream">The stream to decode from.</param>
     /// <param name="metadata">The image metadata.</param>
-    private void ReadXmpProfile(BufferedReadStream stream, ImageMetadata metadata)
+    /// <param name="buffer">Temporary buffer.</param>
+    private void ReadXmpProfile(BufferedReadStream stream, ImageMetadata metadata, Span<byte> buffer)
     {
-        uint xmpChunkSize = this.ReadChunkSize(stream);
+        uint xmpChunkSize = ReadChunkSize(stream, buffer);
         if (this.skipMetadata)
         {
             stream.Skip((int)xmpChunkSize);
@@ -359,9 +362,10 @@ internal sealed class WebpDecoderCore : IImageDecoderInternals, IDisposable
     /// </summary>
     /// <param name="stream">The stream to decode from.</param>
     /// <param name="metadata">The image metadata.</param>
-    private void ReadIccProfile(BufferedReadStream stream, ImageMetadata metadata)
+    /// <param name="buffer">Temporary buffer.</param>
+    private void ReadIccProfile(BufferedReadStream stream, ImageMetadata metadata, Span<byte> buffer)
     {
-        uint iccpChunkSize = this.ReadChunkSize(stream);
+        uint iccpChunkSize = ReadChunkSize(stream, buffer);
         if (this.skipMetadata)
         {
             stream.Skip((int)iccpChunkSize);
@@ -388,22 +392,23 @@ internal sealed class WebpDecoderCore : IImageDecoderInternals, IDisposable
     /// </summary>
     /// <param name="stream">The stream to decode from.</param>
     /// <param name="features">The webp features.</param>
-    private void ReadAnimationParameters(BufferedReadStream stream, WebpFeatures features)
+    /// <param name="buffer">Temporary buffer.</param>
+    private static void ReadAnimationParameters(BufferedReadStream stream, WebpFeatures features, Span<byte> buffer)
     {
         features.Animation = true;
-        uint animationChunkSize = WebpChunkParsingUtils.ReadChunkSize(stream, this.buffer);
+        uint animationChunkSize = WebpChunkParsingUtils.ReadChunkSize(stream, buffer);
         byte blue = (byte)stream.ReadByte();
         byte green = (byte)stream.ReadByte();
         byte red = (byte)stream.ReadByte();
         byte alpha = (byte)stream.ReadByte();
         features.AnimationBackgroundColor = new Color(new Rgba32(red, green, blue, alpha));
-        int bytesRead = stream.Read(this.buffer, 0, 2);
+        int bytesRead = stream.Read(buffer, 0, 2);
         if (bytesRead != 2)
         {
             WebpThrowHelper.ThrowInvalidImageContentException("Not enough data to read the animation loop count");
         }
 
-        features.AnimationLoopCount = BinaryPrimitives.ReadUInt16LittleEndian(this.buffer);
+        features.AnimationLoopCount = BinaryPrimitives.ReadUInt16LittleEndian(buffer);
     }
 
     /// <summary>
@@ -412,9 +417,10 @@ internal sealed class WebpDecoderCore : IImageDecoderInternals, IDisposable
     /// <param name="stream">The stream to decode from.</param>
     /// <param name="features">The features.</param>
     /// <param name="ignoreAlpha">if set to true, skips the chunk data.</param>
-    private void ReadAlphaData(BufferedReadStream stream, WebpFeatures features, bool ignoreAlpha)
+    /// <param name="buffer">Temporary buffer.</param>
+    private void ReadAlphaData(BufferedReadStream stream, WebpFeatures features, bool ignoreAlpha, Span<byte> buffer)
     {
-        uint alphaChunkSize = WebpChunkParsingUtils.ReadChunkSize(stream, this.buffer);
+        uint alphaChunkSize = WebpChunkParsingUtils.ReadChunkSize(stream, buffer);
         if (ignoreAlpha)
         {
             stream.Skip((int)alphaChunkSize);
@@ -436,14 +442,15 @@ internal sealed class WebpDecoderCore : IImageDecoderInternals, IDisposable
     /// Identifies the chunk type from the chunk.
     /// </summary>
     /// <param name="stream">The stream to decode from.</param>
+    /// <param name="buffer">Temporary buffer.</param>
     /// <exception cref="ImageFormatException">
     /// Thrown if the input stream is not valid.
     /// </exception>
-    private WebpChunkType ReadChunkType(BufferedReadStream stream)
+    private static WebpChunkType ReadChunkType(BufferedReadStream stream, Span<byte> buffer)
     {
-        if (stream.Read(this.buffer, 0, 4) == 4)
+        if (stream.Read(buffer, 0, 4) == 4)
         {
-            return (WebpChunkType)BinaryPrimitives.ReadUInt32BigEndian(this.buffer);
+            return (WebpChunkType)BinaryPrimitives.ReadUInt32BigEndian(buffer);
         }
 
         throw new ImageFormatException("Invalid Webp data.");
@@ -454,13 +461,14 @@ internal sealed class WebpDecoderCore : IImageDecoderInternals, IDisposable
     /// so the chunk size will be increased by 1 in those cases.
     /// </summary>
     /// <param name="stream">The stream to decode from.</param>
+    /// <param name="buffer">Temporary buffer.</param>
     /// <returns>The chunk size in bytes.</returns>
     /// <exception cref="ImageFormatException">Invalid data.</exception>
-    private uint ReadChunkSize(BufferedReadStream stream)
+    private static uint ReadChunkSize(BufferedReadStream stream, Span<byte> buffer)
     {
-        if (stream.Read(this.buffer, 0, 4) == 4)
+        if (stream.Read(buffer, 0, 4) == 4)
         {
-            uint chunkSize = BinaryPrimitives.ReadUInt32LittleEndian(this.buffer);
+            uint chunkSize = BinaryPrimitives.ReadUInt32LittleEndian(buffer);
             return (chunkSize % 2 == 0) ? chunkSize : chunkSize + 1;
         }
 

src/ImageSharp/Metadata/Profiles/Exif/ExifReader.cs

@@ -86,10 +86,6 @@ internal class ExifReader : BaseExifReader
 /// </summary>
 internal abstract class BaseExifReader
 {
-    private readonly byte[] buf8 = new byte[8];
-    private readonly byte[] buf4 = new byte[4];
-    private readonly byte[] buf2 = new byte[2];
-
     private readonly MemoryAllocator? allocator;
     private readonly Stream data;
     private List<ExifTag>? invalidTags;
@@ -528,20 +524,33 @@ internal abstract class BaseExifReader
         return read == length;
     }
 
-    protected ulong ReadUInt64() =>
-        this.TryReadSpan(this.buf8)
-            ? this.ConvertToUInt64(this.buf8)
+    protected ulong ReadUInt64()
+    {
+        Span<byte> buffer = stackalloc byte[8];
+
+        return this.TryReadSpan(buffer)
+            ? this.ConvertToUInt64(buffer)
             : default;
+    }
 
     // Known as Long in Exif Specification.
-    protected uint ReadUInt32() =>
-        this.TryReadSpan(this.buf4)
-            ? this.ConvertToUInt32(this.buf4)
+    protected uint ReadUInt32()
+    {
+        Span<byte> buffer = stackalloc byte[4];
+
+        return this.TryReadSpan(buffer)
+            ? this.ConvertToUInt32(buffer)
             : default;
+    }
 
-    protected ushort ReadUInt16() => this.TryReadSpan(this.buf2)
-            ? this.ConvertToShort(this.buf2)
+    protected ushort ReadUInt16()
+    {
+        Span<byte> buffer = stackalloc byte[2];
+
+        return this.TryReadSpan(buffer)
+            ? this.ConvertToShort(buffer)
             : default;
+    }
 
     private long ConvertToInt64(ReadOnlySpan<byte> buffer)
     {

src/ImageSharp/Metadata/Profiles/Exif/Values/ExifByteArray.cs

@@ -45,12 +45,12 @@ internal sealed class ExifByteArray : ExifArrayValue<byte>
 
     private bool TrySetSignedIntArray(int[] intArrayValue)
     {
-        if (Array.FindIndex(intArrayValue, x => x < byte.MinValue || x > byte.MaxValue) > -1)
+        if (Array.FindIndex(intArrayValue, x => (uint)x > byte.MaxValue) >= 0)
         {
             return false;
         }
 
-        var value = new byte[intArrayValue.Length];
+        byte[] value = new byte[intArrayValue.Length];
         for (int i = 0; i < intArrayValue.Length; i++)
         {
             int s = intArrayValue[i];

src/ImageSharp/Metadata/Profiles/ICC/IccProfile.cs

@@ -108,10 +108,10 @@ public sealed class IccProfile : IDeepCloneable<IccProfile>
         const int profileIdPos = 84;
 
         // need to copy some values because they need to be zero for the hashing
-        byte[] temp = new byte[24];
-        Buffer.BlockCopy(data, profileFlagPos, temp, 0, 4);
-        Buffer.BlockCopy(data, renderingIntentPos, temp, 4, 4);
-        Buffer.BlockCopy(data, profileIdPos, temp, 8, 16);
+        Span<byte> temp = stackalloc byte[24];
+        data.AsSpan(profileFlagPos, 4).CopyTo(temp);
+        data.AsSpan(renderingIntentPos, 4).CopyTo(temp.Slice(4));
+        data.AsSpan(profileIdPos, 16).CopyTo(temp.Slice(8));
 
         try
         {
@@ -131,9 +131,9 @@ public sealed class IccProfile : IDeepCloneable<IccProfile>
         }
         finally
         {
-            Buffer.BlockCopy(temp, 0, data, profileFlagPos, 4);
-            Buffer.BlockCopy(temp, 4, data, renderingIntentPos, 4);
-            Buffer.BlockCopy(temp, 8, data, profileIdPos, 16);
+            temp.Slice(0, 4).CopyTo(data.AsSpan(profileFlagPos));
+            temp.Slice(4, 4).CopyTo(data.AsSpan(renderingIntentPos));
+            temp.Slice(8, 16).CopyTo(data.AsSpan(profileIdPos));
         }
     }
 

tests/ImageSharp.Tests/Formats/Tiff/BigTiffMetadataTests.cs

@@ -211,8 +211,8 @@ public class BigTiffMetadataTests
 
         foreach (IExifValue entry in values)
         {
-            writer.Write((ushort)entry.Tag);
-            writer.Write((ushort)entry.DataType);
+            writer.Write((ushort)entry.Tag, buffer);
+            writer.Write((ushort)entry.DataType, buffer);
             WriteLong8(writer, buffer, ExifWriter.GetNumberOfComponents(entry));
 
             uint length = ExifWriter.GetLength(entry);

tests/ImageSharp.Tests/Formats/Tiff/TiffEncoderHeaderTests.cs

@@ -19,7 +19,7 @@ public class TiffEncoderHeaderTests
 
         using (TiffStreamWriter writer = new(stream))
         {
-            long firstIfdMarker = TiffEncoderCore.WriteHeader(writer);
+            long firstIfdMarker = TiffEncoderCore.WriteHeader(writer, stackalloc byte[4]);
         }
 
         Assert.Equal(new byte[] { 0x49, 0x49, 42, 0, 0x00, 0x00, 0x00, 0x00 }, stream.ToArray());
@@ -32,7 +32,7 @@ public class TiffEncoderHeaderTests
         TiffEncoderCore encoder = new(Encoder, Configuration.Default.MemoryAllocator);
 
         using TiffStreamWriter writer = new(stream);
-        long firstIfdMarker = TiffEncoderCore.WriteHeader(writer);
+        long firstIfdMarker = TiffEncoderCore.WriteHeader(writer, stackalloc byte[4]);
         Assert.Equal(4, firstIfdMarker);
     }
 }

tests/ImageSharp.Tests/Formats/Tiff/Utils/TiffWriterTests.cs

@@ -53,7 +53,7 @@ public class TiffWriterTests
     {
         using var stream = new MemoryStream();
         using var writer = new TiffStreamWriter(stream);
-        writer.Write(1234);
+        writer.Write(1234, stackalloc byte[2]);
 
         Assert.Equal(new byte[] { 0xD2, 0x04 }, stream.ToArray());
     }
@@ -63,7 +63,7 @@ public class TiffWriterTests
     {
         using var stream = new MemoryStream();
         using var writer = new TiffStreamWriter(stream);
-        writer.Write(12345678U);
+        writer.Write(12345678U, stackalloc byte[4]);
 
         Assert.Equal(new byte[] { 0x4E, 0x61, 0xBC, 0x00 }, stream.ToArray());
     }
@@ -89,16 +89,17 @@ public class TiffWriterTests
     public void WriteMarker_WritesToPlacedPosition()
     {
         using var stream = new MemoryStream();
+        Span<byte> buffer = stackalloc byte[4];
 
         using (var writer = new TiffStreamWriter(stream))
         {
-            writer.Write(0x11111111);
-            long marker = writer.PlaceMarker();
-            writer.Write(0x33333333);
+            writer.Write(0x11111111, buffer);
+            long marker = writer.PlaceMarker(buffer);
+            writer.Write(0x33333333, buffer);
 
-            writer.WriteMarker(marker, 0x12345678);
+            writer.WriteMarker(marker, 0x12345678, buffer);
 
-            writer.Write(0x44444444);
+            writer.Write(0x44444444, buffer);
         }
 
         Assert.Equal(