From b44625e9d17c55462c086eec20c7f084dc5cc428 Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Tue, 20 Mar 2018 18:05:12 -0700
Subject: [PATCH] Use ReadOnlySpans and BinaryPrimitives

---
 src/ImageSharp/Formats/Png/PngDecoderCore.cs  | 41 ++++++++-----------
 src/ImageSharp/Formats/Png/PngEncoderCore.cs  | 23 +++--------
 src/ImageSharp/Memory/SpanHelper.cs           |  4 +-
 .../PixelOperations{TPixel}.Generated.cs      | 32 +++++++--------
 .../PixelOperations{TPixel}.Generated.tt      |  8 ++--
 .../Rgba32.PixelOperations.Generated.cs       | 12 +++---
 .../PixelFormats/PixelOperations{TPixel}.cs   | 10 ++---
 .../PixelFormats/Rgba32.PixelOperations.cs    | 12 +++---
 .../RgbaVector.PixelOperations.cs             |  2 +-
 9 files changed, 63 insertions(+), 81 deletions(-)

diff --git a/src/ImageSharp/Formats/Png/PngDecoderCore.cs b/src/ImageSharp/Formats/Png/PngDecoderCore.cs
index dba4eaa15c..fbb5c29a47 100644
--- a/src/ImageSharp/Formats/Png/PngDecoderCore.cs
+++ b/src/ImageSharp/Formats/Png/PngDecoderCore.cs
@@ -3,6 +3,7 @@
 
 using System;
 using System.Buffers;
+using System.Buffers.Binary;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
@@ -414,14 +415,11 @@ namespace SixLabors.ImageSharp.Formats.Png
         /// </summary>
         /// <param name="metadata">The metadata to read to.</param>
         /// <param name="data">The data containing physical data.</param>
-        private void ReadPhysicalChunk(ImageMetaData metadata, byte[] data)
+        private void ReadPhysicalChunk(ImageMetaData metadata, ReadOnlySpan<byte> data)
         {
-            data.ReverseBytes(0, 4);
-            data.ReverseBytes(4, 4);
-
             // 39.3700787 = inches in a meter.
-            metadata.HorizontalResolution = BitConverter.ToInt32(data, 0) / 39.3700787d;
-            metadata.VerticalResolution = BitConverter.ToInt32(data, 4) / 39.3700787d;
+            metadata.HorizontalResolution = BinaryPrimitives.ReadInt32BigEndian(data.Slice(0, 4)) / 39.3700787d;
+            metadata.VerticalResolution = BinaryPrimitives.ReadInt32BigEndian(data.Slice(4, 4)) / 39.3700787d;
         }
 
         /// <summary>
@@ -699,14 +697,14 @@ namespace SixLabors.ImageSharp.Formats.Png
         /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <param name="defilteredScanline">The de-filtered scanline</param>
         /// <param name="pixels">The image</param>
-        private void ProcessDefilteredScanline<TPixel>(byte[] defilteredScanline, ImageFrame<TPixel> pixels)
+        private void ProcessDefilteredScanline<TPixel>(Span<byte> defilteredScanline, ImageFrame<TPixel> pixels)
             where TPixel : struct, IPixel<TPixel>
         {
             var color = default(TPixel);
             Span<TPixel> rowSpan = pixels.GetPixelRowSpan(this.currentRow);
 
             // Trim the first marker byte from the buffer
-            var scanlineBuffer = new Span<byte>(defilteredScanline, 1, defilteredScanline.Length - 1);
+            Span<byte> scanlineBuffer = defilteredScanline.Slice(1, defilteredScanline.Length - 1);
 
             switch (this.pngColorType)
             {
@@ -1159,22 +1157,19 @@ namespace SixLabors.ImageSharp.Formats.Png
         /// <summary>
         /// Reads a header chunk from the data.
         /// </summary>
-        /// <param name="data">The <see cref="T:byte[]"/> containing  data.</param>
-        private void ReadHeaderChunk(byte[] data)
+        /// <param name="data">The <see cref="T:Span<byte>"/> containing  data.</param>
+        private void ReadHeaderChunk(ReadOnlySpan<byte> data)
         {
-            this.header = new PngHeader();
-
-            data.ReverseBytes(0, 4);
-            data.ReverseBytes(4, 4);
-
-            this.header.Width = BitConverter.ToInt32(data, 0);
-            this.header.Height = BitConverter.ToInt32(data, 4);
-
-            this.header.BitDepth = data[8];
-            this.header.ColorType = (PngColorType)data[9];
-            this.header.CompressionMethod = data[10];
-            this.header.FilterMethod = data[11];
-            this.header.InterlaceMethod = (PngInterlaceMode)data[12];
+            this.header = new PngHeader
+            {
+                Width = BinaryPrimitives.ReadInt32BigEndian(data.Slice(0, 4)),
+                Height = BinaryPrimitives.ReadInt32BigEndian(data.Slice(4, 4)),
+                BitDepth = data[8],
+                ColorType = (PngColorType)data[9],
+                CompressionMethod = data[10],
+                FilterMethod = data[11],
+                InterlaceMethod = (PngInterlaceMode)data[12]
+            };
         }
 
         /// <summary>
diff --git a/src/ImageSharp/Formats/Png/PngEncoderCore.cs b/src/ImageSharp/Formats/Png/PngEncoderCore.cs
index 2735164996..7ae075569d 100644
--- a/src/ImageSharp/Formats/Png/PngEncoderCore.cs
+++ b/src/ImageSharp/Formats/Png/PngEncoderCore.cs
@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System;
+using System.Buffers.Binary;
 using System.IO;
 using System.Linq;
 using SixLabors.ImageSharp.Advanced;
@@ -243,20 +244,6 @@ namespace SixLabors.ImageSharp.Formats.Png
             this.paeth?.Dispose();
         }
 
-        /// <summary>
-        /// Writes an integer to the byte array.
-        /// </summary>
-        /// <param name="data">The <see cref="T:byte[]"/> containing image data.</param>
-        /// <param name="offset">The amount to offset by.</param>
-        /// <param name="value">The value to write.</param>
-        private static void WriteInteger(byte[] data, int offset, int value)
-        {
-            byte[] buffer = BitConverter.GetBytes(value);
-
-            buffer.ReverseBytes();
-            Buffer.BlockCopy(buffer, 0, data, offset, 4);
-        }
-
         /// <summary>
         /// Writes an integer to the stream.
         /// </summary>
@@ -450,8 +437,8 @@ namespace SixLabors.ImageSharp.Formats.Png
         /// <param name="header">The <see cref="PngHeader"/>.</param>
         private void WriteHeaderChunk(Stream stream, PngHeader header)
         {
-            WriteInteger(this.chunkDataBuffer, 0, header.Width);
-            WriteInteger(this.chunkDataBuffer, 4, header.Height);
+            BinaryPrimitives.WriteInt32BigEndian(new Span<byte>(this.chunkDataBuffer, 0, 4), header.Width);
+            BinaryPrimitives.WriteInt32BigEndian(new Span<byte>(this.chunkDataBuffer, 4, 4), header.Height);
 
             this.chunkDataBuffer[8] = header.BitDepth;
             this.chunkDataBuffer[9] = (byte)header.ColorType;
@@ -535,8 +522,8 @@ namespace SixLabors.ImageSharp.Formats.Png
                 int dpmX = (int)Math.Round(image.MetaData.HorizontalResolution * 39.3700787D);
                 int dpmY = (int)Math.Round(image.MetaData.VerticalResolution * 39.3700787D);
 
-                WriteInteger(this.chunkDataBuffer, 0, dpmX);
-                WriteInteger(this.chunkDataBuffer, 4, dpmY);
+                BinaryPrimitives.WriteInt32BigEndian(this.chunkDataBuffer.AsSpan().Slice(0, 4), dpmX);
+                BinaryPrimitives.WriteInt32BigEndian(this.chunkDataBuffer.AsSpan().Slice(4, 4), dpmY);
 
                 this.chunkDataBuffer[8] = 1;
 
diff --git a/src/ImageSharp/Memory/SpanHelper.cs b/src/ImageSharp/Memory/SpanHelper.cs
index 0c327484a0..3bad54a12b 100644
--- a/src/ImageSharp/Memory/SpanHelper.cs
+++ b/src/ImageSharp/Memory/SpanHelper.cs
@@ -34,7 +34,7 @@ namespace SixLabors.ImageSharp.Memory
         /// <param name="destination">The destination <see cref="Span{T}"/>.</param>
         /// <param name="count">The number of elements to copy</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static unsafe void Copy<T>(Span<T> source, Span<T> destination, int count)
+        public static unsafe void Copy<T>(ReadOnlySpan<T> source, Span<T> destination, int count)
             where T : struct
         {
             DebugGuard.MustBeLessThanOrEqualTo(count, source.Length, nameof(count));
@@ -66,7 +66,7 @@ namespace SixLabors.ImageSharp.Memory
         /// <param name="source">The <see cref="Span{T}"/> to copy elements from.</param>
         /// <param name="destination">The destination <see cref="Span{T}"/>.</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static void Copy<T>(Span<T> source, Span<T> destination)
+        public static void Copy<T>(ReadOnlySpan<T> source, Span<T> destination)
             where T : struct
         {
             Copy(source, destination, Math.Min(source.Length, destination.Length));
diff --git a/src/ImageSharp/PixelFormats/Generated/PixelOperations{TPixel}.Generated.cs b/src/ImageSharp/PixelFormats/Generated/PixelOperations{TPixel}.Generated.cs
index 9505ee6cf7..904e27c7f2 100644
--- a/src/ImageSharp/PixelFormats/Generated/PixelOperations{TPixel}.Generated.cs
+++ b/src/ImageSharp/PixelFormats/Generated/PixelOperations{TPixel}.Generated.cs
@@ -17,7 +17,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="source">The source <see cref="Span{T}"/> of <see cref="Rgba32"/> data.</param>
         /// <param name="destPixels">The <see cref="Span{T}"/> to the destination pixels.</param>
         /// <param name="count">The number of pixels to convert.</param>
-        internal virtual void PackFromRgba32(Span<Rgba32> source, Span<TPixel> destPixels, int count)
+        internal virtual void PackFromRgba32(ReadOnlySpan<Rgba32> source, Span<TPixel> destPixels, int count)
         {
 			GuardSpans(source, nameof(source), destPixels, nameof(destPixels), count);
             
@@ -42,7 +42,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="destPixels">The <see cref="Span{T}"/> to the destination pixels.</param>
         /// <param name="count">The number of pixels to convert.</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        internal void PackFromRgba32Bytes(Span<byte> sourceBytes, Span<TPixel> destPixels, int count)
+        internal void PackFromRgba32Bytes(ReadOnlySpan<byte> sourceBytes, Span<TPixel> destPixels, int count)
         {
             this.PackFromRgba32(sourceBytes.NonPortableCast<byte, Rgba32>(), destPixels, count);
         }
@@ -54,7 +54,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="sourcePixels">The span of source pixels</param>
         /// <param name="dest">The destination span of <see cref="Rgba32"/> data.</param>
         /// <param name="count">The number of pixels to convert.</param>
-        internal virtual void ToRgba32(Span<TPixel> sourcePixels, Span<Rgba32> dest, int count)
+        internal virtual void ToRgba32(ReadOnlySpan<TPixel> sourcePixels, Span<Rgba32> dest, int count)
         {
             GuardSpans(sourcePixels, nameof(sourcePixels), dest, nameof(dest), count);
 
@@ -77,7 +77,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="destBytes">The <see cref="Span{T}"/> to the destination bytes.</param>
         /// <param name="count">The number of pixels to convert.</param>
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
-        internal void ToRgba32Bytes(Span<TPixel> sourceColors, Span<byte> destBytes, int count)
+        internal void ToRgba32Bytes(ReadOnlySpan<TPixel> sourceColors, Span<byte> destBytes, int count)
         {
             this.ToRgba32(sourceColors, destBytes.NonPortableCast<byte, Rgba32>(), count);
         }
@@ -88,7 +88,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="source">The source <see cref="Span{T}"/> of <see cref="Bgra32"/> data.</param>
         /// <param name="destPixels">The <see cref="Span{T}"/> to the destination pixels.</param>
         /// <param name="count">The number of pixels to convert.</param>
-        internal virtual void PackFromBgra32(Span<Bgra32> source, Span<TPixel> destPixels, int count)
+        internal virtual void PackFromBgra32(ReadOnlySpan<Bgra32> source, Span<TPixel> destPixels, int count)
         {
 			GuardSpans(source, nameof(source), destPixels, nameof(destPixels), count);
             
@@ -113,7 +113,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="destPixels">The <see cref="Span{T}"/> to the destination pixels.</param>
         /// <param name="count">The number of pixels to convert.</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        internal void PackFromBgra32Bytes(Span<byte> sourceBytes, Span<TPixel> destPixels, int count)
+        internal void PackFromBgra32Bytes(ReadOnlySpan<byte> sourceBytes, Span<TPixel> destPixels, int count)
         {
             this.PackFromBgra32(sourceBytes.NonPortableCast<byte, Bgra32>(), destPixels, count);
         }
@@ -125,7 +125,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="sourcePixels">The span of source pixels</param>
         /// <param name="dest">The destination span of <see cref="Bgra32"/> data.</param>
         /// <param name="count">The number of pixels to convert.</param>
-        internal virtual void ToBgra32(Span<TPixel> sourcePixels, Span<Bgra32> dest, int count)
+        internal virtual void ToBgra32(ReadOnlySpan<TPixel> sourcePixels, Span<Bgra32> dest, int count)
         {
             GuardSpans(sourcePixels, nameof(sourcePixels), dest, nameof(dest), count);
 
@@ -148,7 +148,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="destBytes">The <see cref="Span{T}"/> to the destination bytes.</param>
         /// <param name="count">The number of pixels to convert.</param>
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
-        internal void ToBgra32Bytes(Span<TPixel> sourceColors, Span<byte> destBytes, int count)
+        internal void ToBgra32Bytes(ReadOnlySpan<TPixel> sourceColors, Span<byte> destBytes, int count)
         {
             this.ToBgra32(sourceColors, destBytes.NonPortableCast<byte, Bgra32>(), count);
         }
@@ -159,7 +159,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="source">The source <see cref="Span{T}"/> of <see cref="Rgb24"/> data.</param>
         /// <param name="destPixels">The <see cref="Span{T}"/> to the destination pixels.</param>
         /// <param name="count">The number of pixels to convert.</param>
-        internal virtual void PackFromRgb24(Span<Rgb24> source, Span<TPixel> destPixels, int count)
+        internal virtual void PackFromRgb24(ReadOnlySpan<Rgb24> source, Span<TPixel> destPixels, int count)
         {
 			GuardSpans(source, nameof(source), destPixels, nameof(destPixels), count);
             
@@ -184,7 +184,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="destPixels">The <see cref="Span{T}"/> to the destination pixels.</param>
         /// <param name="count">The number of pixels to convert.</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        internal void PackFromRgb24Bytes(Span<byte> sourceBytes, Span<TPixel> destPixels, int count)
+        internal void PackFromRgb24Bytes(ReadOnlySpan<byte> sourceBytes, Span<TPixel> destPixels, int count)
         {
             this.PackFromRgb24(sourceBytes.NonPortableCast<byte, Rgb24>(), destPixels, count);
         }
@@ -196,7 +196,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="sourcePixels">The span of source pixels</param>
         /// <param name="dest">The destination span of <see cref="Rgb24"/> data.</param>
         /// <param name="count">The number of pixels to convert.</param>
-        internal virtual void ToRgb24(Span<TPixel> sourcePixels, Span<Rgb24> dest, int count)
+        internal virtual void ToRgb24(ReadOnlySpan<TPixel> sourcePixels, Span<Rgb24> dest, int count)
         {
             GuardSpans(sourcePixels, nameof(sourcePixels), dest, nameof(dest), count);
 
@@ -219,7 +219,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="destBytes">The <see cref="Span{T}"/> to the destination bytes.</param>
         /// <param name="count">The number of pixels to convert.</param>
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
-        internal void ToRgb24Bytes(Span<TPixel> sourceColors, Span<byte> destBytes, int count)
+        internal void ToRgb24Bytes(ReadOnlySpan<TPixel> sourceColors, Span<byte> destBytes, int count)
         {
             this.ToRgb24(sourceColors, destBytes.NonPortableCast<byte, Rgb24>(), count);
         }
@@ -230,7 +230,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="source">The source <see cref="Span{T}"/> of <see cref="Bgr24"/> data.</param>
         /// <param name="destPixels">The <see cref="Span{T}"/> to the destination pixels.</param>
         /// <param name="count">The number of pixels to convert.</param>
-        internal virtual void PackFromBgr24(Span<Bgr24> source, Span<TPixel> destPixels, int count)
+        internal virtual void PackFromBgr24(ReadOnlySpan<Bgr24> source, Span<TPixel> destPixels, int count)
         {
 			GuardSpans(source, nameof(source), destPixels, nameof(destPixels), count);
             
@@ -255,7 +255,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="destPixels">The <see cref="Span{T}"/> to the destination pixels.</param>
         /// <param name="count">The number of pixels to convert.</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        internal void PackFromBgr24Bytes(Span<byte> sourceBytes, Span<TPixel> destPixels, int count)
+        internal void PackFromBgr24Bytes(ReadOnlySpan<byte> sourceBytes, Span<TPixel> destPixels, int count)
         {
             this.PackFromBgr24(sourceBytes.NonPortableCast<byte, Bgr24>(), destPixels, count);
         }
@@ -267,7 +267,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="sourcePixels">The span of source pixels</param>
         /// <param name="dest">The destination span of <see cref="Bgr24"/> data.</param>
         /// <param name="count">The number of pixels to convert.</param>
-        internal virtual void ToBgr24(Span<TPixel> sourcePixels, Span<Bgr24> dest, int count)
+        internal virtual void ToBgr24(ReadOnlySpan<TPixel> sourcePixels, Span<Bgr24> dest, int count)
         {
             GuardSpans(sourcePixels, nameof(sourcePixels), dest, nameof(dest), count);
 
@@ -290,7 +290,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="destBytes">The <see cref="Span{T}"/> to the destination bytes.</param>
         /// <param name="count">The number of pixels to convert.</param>
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
-        internal void ToBgr24Bytes(Span<TPixel> sourceColors, Span<byte> destBytes, int count)
+        internal void ToBgr24Bytes(ReadOnlySpan<TPixel> sourceColors, Span<byte> destBytes, int count)
         {
             this.ToBgr24(sourceColors, destBytes.NonPortableCast<byte, Bgr24>(), count);
         }
diff --git a/src/ImageSharp/PixelFormats/Generated/PixelOperations{TPixel}.Generated.tt b/src/ImageSharp/PixelFormats/Generated/PixelOperations{TPixel}.Generated.tt
index 365f5cb514..999fe66107 100644
--- a/src/ImageSharp/PixelFormats/Generated/PixelOperations{TPixel}.Generated.tt
+++ b/src/ImageSharp/PixelFormats/Generated/PixelOperations{TPixel}.Generated.tt
@@ -21,7 +21,7 @@
         /// <param name="sourcePixels">The span of source pixels</param>
         /// <param name="dest">The destination span of <see cref="<#=pixelType#>"/> data.</param>
         /// <param name="count">The number of pixels to convert.</param>
-        internal virtual void To<#=pixelType#>(Span<TPixel> sourcePixels, Span<<#=pixelType#>> dest, int count)
+        internal virtual void To<#=pixelType#>(ReadOnlySpan<TPixel> sourcePixels, Span<<#=pixelType#>> dest, int count)
         {
             GuardSpans(sourcePixels, nameof(sourcePixels), dest, nameof(dest), count);
 
@@ -44,7 +44,7 @@
         /// <param name="destBytes">The <see cref="Span{T}"/> to the destination bytes.</param>
         /// <param name="count">The number of pixels to convert.</param>
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
-        internal void To<#=pixelType#>Bytes(Span<TPixel> sourceColors, Span<byte> destBytes, int count)
+        internal void To<#=pixelType#>Bytes(ReadOnlySpan<TPixel> sourceColors, Span<byte> destBytes, int count)
         {
             this.To<#=pixelType#>(sourceColors, destBytes.NonPortableCast<byte, <#=pixelType#>>(), count);
         }
@@ -61,7 +61,7 @@
         /// <param name="source">The source <see cref="Span{T}"/> of <see cref="<#=pixelType#>"/> data.</param>
         /// <param name="destPixels">The <see cref="Span{T}"/> to the destination pixels.</param>
         /// <param name="count">The number of pixels to convert.</param>
-        internal virtual void PackFrom<#=pixelType#>(Span<<#=pixelType#>> source, Span<TPixel> destPixels, int count)
+        internal virtual void PackFrom<#=pixelType#>(ReadOnlySpan<<#=pixelType#>> source, Span<TPixel> destPixels, int count)
         {
 			GuardSpans(source, nameof(source), destPixels, nameof(destPixels), count);
             
@@ -86,7 +86,7 @@
         /// <param name="destPixels">The <see cref="Span{T}"/> to the destination pixels.</param>
         /// <param name="count">The number of pixels to convert.</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        internal void PackFrom<#=pixelType#>Bytes(Span<byte> sourceBytes, Span<TPixel> destPixels, int count)
+        internal void PackFrom<#=pixelType#>Bytes(ReadOnlySpan<byte> sourceBytes, Span<TPixel> destPixels, int count)
         {
             this.PackFrom<#=pixelType#>(sourceBytes.NonPortableCast<byte, <#=pixelType#>>(), destPixels, count);
         }
diff --git a/src/ImageSharp/PixelFormats/Generated/Rgba32.PixelOperations.Generated.cs b/src/ImageSharp/PixelFormats/Generated/Rgba32.PixelOperations.Generated.cs
index c5ee6661f7..a8e68e36db 100644
--- a/src/ImageSharp/PixelFormats/Generated/Rgba32.PixelOperations.Generated.cs
+++ b/src/ImageSharp/PixelFormats/Generated/Rgba32.PixelOperations.Generated.cs
@@ -17,7 +17,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         {
 			
 			/// <inheritdoc />
-            internal override void PackFromRgb24(Span<Rgb24> source, Span<Rgba32> destPixels, int count)
+            internal override void PackFromRgb24(ReadOnlySpan<Rgb24> source, Span<Rgba32> destPixels, int count)
             {
                 GuardSpans(source, nameof(source), destPixels, nameof(destPixels), count);
 
@@ -33,7 +33,7 @@ namespace SixLabors.ImageSharp.PixelFormats
             }
 		
 			/// <inheritdoc />
-            internal override void ToRgb24(Span<Rgba32> sourcePixels, Span<Rgb24> dest, int count)
+            internal override void ToRgb24(ReadOnlySpan<Rgba32> sourcePixels, Span<Rgb24> dest, int count)
             {
                 GuardSpans(sourcePixels, nameof(sourcePixels), dest, nameof(dest), count);
 
@@ -49,7 +49,7 @@ namespace SixLabors.ImageSharp.PixelFormats
             }
 		
 			/// <inheritdoc />
-            internal override void PackFromBgr24(Span<Bgr24> source, Span<Rgba32> destPixels, int count)
+            internal override void PackFromBgr24(ReadOnlySpan<Bgr24> source, Span<Rgba32> destPixels, int count)
             {
                 GuardSpans(source, nameof(source), destPixels, nameof(destPixels), count);
 
@@ -65,7 +65,7 @@ namespace SixLabors.ImageSharp.PixelFormats
             }
 		
 			/// <inheritdoc />
-            internal override void ToBgr24(Span<Rgba32> sourcePixels, Span<Bgr24> dest, int count)
+            internal override void ToBgr24(ReadOnlySpan<Rgba32> sourcePixels, Span<Bgr24> dest, int count)
             {
                 GuardSpans(sourcePixels, nameof(sourcePixels), dest, nameof(dest), count);
 
@@ -81,7 +81,7 @@ namespace SixLabors.ImageSharp.PixelFormats
             }
 		
 			/// <inheritdoc />
-            internal override void PackFromBgra32(Span<Bgra32> source, Span<Rgba32> destPixels, int count)
+            internal override void PackFromBgra32(ReadOnlySpan<Bgra32> source, Span<Rgba32> destPixels, int count)
             {
                 GuardSpans(source, nameof(source), destPixels, nameof(destPixels), count);
 
@@ -97,7 +97,7 @@ namespace SixLabors.ImageSharp.PixelFormats
             }
 		
 			/// <inheritdoc />
-            internal override void ToBgra32(Span<Rgba32> sourcePixels, Span<Bgra32> dest, int count)
+            internal override void ToBgra32(ReadOnlySpan<Rgba32> sourcePixels, Span<Bgra32> dest, int count)
             {
                 GuardSpans(sourcePixels, nameof(sourcePixels), dest, nameof(dest), count);
 
diff --git a/src/ImageSharp/PixelFormats/PixelOperations{TPixel}.cs b/src/ImageSharp/PixelFormats/PixelOperations{TPixel}.cs
index 6f79752406..e6238bf5a6 100644
--- a/src/ImageSharp/PixelFormats/PixelOperations{TPixel}.cs
+++ b/src/ImageSharp/PixelFormats/PixelOperations{TPixel}.cs
@@ -27,7 +27,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="sourceVectors">The <see cref="Span{T}"/> to the source vectors.</param>
         /// <param name="destColors">The <see cref="Span{T}"/> to the destination colors.</param>
         /// <param name="count">The number of pixels to convert.</param>
-        internal virtual void PackFromVector4(Span<Vector4> sourceVectors, Span<TPixel> destColors, int count)
+        internal virtual void PackFromVector4(ReadOnlySpan<Vector4> sourceVectors, Span<TPixel> destColors, int count)
         {
             GuardSpans(sourceVectors, nameof(sourceVectors), destColors, nameof(destColors), count);
 
@@ -48,7 +48,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="sourceColors">The <see cref="Span{T}"/> to the source colors.</param>
         /// <param name="destVectors">The <see cref="Span{T}"/> to the destination vectors.</param>
         /// <param name="count">The number of pixels to convert.</param>
-        internal virtual void ToVector4(Span<TPixel> sourceColors, Span<Vector4> destVectors, int count)
+        internal virtual void ToVector4(ReadOnlySpan<TPixel> sourceColors, Span<Vector4> destVectors, int count)
         {
             GuardSpans(sourceColors, nameof(sourceColors), destVectors, nameof(destVectors), count);
 
@@ -75,14 +75,14 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="destParamName">The destination parameter name</param>
         /// <param name="minLength">The minimum length</param>
         protected internal static void GuardSpans<TSource, TDest>(
-            Span<TSource> source,
+            ReadOnlySpan<TSource> source,
             string sourceParamName,
             Span<TDest> dest,
             string destParamName,
             int minLength)
         {
-            Guard.MustBeSizedAtLeast(source, minLength, sourceParamName);
-            Guard.MustBeSizedAtLeast(dest, minLength, destParamName);
+            Guard.MustBeSizedAtLeast<TSource>(source, minLength, sourceParamName);
+            Guard.MustBeSizedAtLeast<TDest>(dest, minLength, destParamName);
         }
     }
 }
\ No newline at end of file
diff --git a/src/ImageSharp/PixelFormats/Rgba32.PixelOperations.cs b/src/ImageSharp/PixelFormats/Rgba32.PixelOperations.cs
index d87820f847..a7e5736b0e 100644
--- a/src/ImageSharp/PixelFormats/Rgba32.PixelOperations.cs
+++ b/src/ImageSharp/PixelFormats/Rgba32.PixelOperations.cs
@@ -36,7 +36,7 @@ namespace SixLabors.ImageSharp.PixelFormats
             ///     <cref>https://github.com/dotnet/corefx/issues/15957</cref>
             /// </see>
             /// </remarks>
-            internal static void ToVector4SimdAligned(Span<Rgba32> sourceColors, Span<Vector4> destVectors, int count)
+            internal static void ToVector4SimdAligned(ReadOnlySpan<Rgba32> sourceColors, Span<Vector4> destVectors, int count)
             {
                 if (!Vector.IsHardwareAccelerated)
                 {
@@ -87,7 +87,7 @@ namespace SixLabors.ImageSharp.PixelFormats
             }
 
             /// <inheritdoc />
-            internal override void ToVector4(Span<Rgba32> sourceColors, Span<Vector4> destVectors, int count)
+            internal override void ToVector4(ReadOnlySpan<Rgba32> sourceColors, Span<Vector4> destVectors, int count)
             {
                 Guard.MustBeSizedAtLeast(sourceColors, count, nameof(sourceColors));
                 Guard.MustBeSizedAtLeast(destVectors, count, nameof(destVectors));
@@ -115,7 +115,7 @@ namespace SixLabors.ImageSharp.PixelFormats
                 }
             }
 
-            internal override void PackFromVector4(Span<Vector4> sourceVectors, Span<Rgba32> destColors, int count)
+            internal override void PackFromVector4(ReadOnlySpan<Vector4> sourceVectors, Span<Rgba32> destColors, int count)
             {
                 GuardSpans(sourceVectors, nameof(sourceVectors), destColors, nameof(destColors), count);
 
@@ -130,7 +130,7 @@ namespace SixLabors.ImageSharp.PixelFormats
 
                 if (alignedCount > 0)
                 {
-                    Span<float> flatSrc = sourceVectors.Slice(0, alignedCount).NonPortableCast<Vector4, float>();
+                    ReadOnlySpan<float> flatSrc = sourceVectors.Slice(0, alignedCount).NonPortableCast<Vector4, float>();
                     Span<byte> flatDest = destColors.NonPortableCast<Rgba32, byte>();
 
                     SimdUtils.BulkConvertNormalizedFloatToByteClampOverflows(flatSrc, flatDest);
@@ -145,7 +145,7 @@ namespace SixLabors.ImageSharp.PixelFormats
             }
 
             /// <inheritdoc />
-            internal override void PackFromRgba32(Span<Rgba32> source, Span<Rgba32> destPixels, int count)
+            internal override void PackFromRgba32(ReadOnlySpan<Rgba32> source, Span<Rgba32> destPixels, int count)
             {
                 GuardSpans(source, nameof(source), destPixels, nameof(destPixels), count);
 
@@ -153,7 +153,7 @@ namespace SixLabors.ImageSharp.PixelFormats
             }
 
             /// <inheritdoc />
-            internal override void ToRgba32(Span<Rgba32> sourcePixels, Span<Rgba32> dest, int count)
+            internal override void ToRgba32(ReadOnlySpan<Rgba32> sourcePixels, Span<Rgba32> dest, int count)
             {
                 GuardSpans(sourcePixels, nameof(sourcePixels), dest, nameof(dest), count);
 
diff --git a/src/ImageSharp/PixelFormats/RgbaVector.PixelOperations.cs b/src/ImageSharp/PixelFormats/RgbaVector.PixelOperations.cs
index 1886df29f1..f038eaa910 100644
--- a/src/ImageSharp/PixelFormats/RgbaVector.PixelOperations.cs
+++ b/src/ImageSharp/PixelFormats/RgbaVector.PixelOperations.cs
@@ -18,7 +18,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         internal class PixelOperations : PixelOperations<RgbaVector>
         {
             /// <inheritdoc />
-            internal override unsafe void ToVector4(Span<RgbaVector> sourceColors, Span<Vector4> destVectors, int count)
+            internal override unsafe void ToVector4(ReadOnlySpan<RgbaVector> sourceColors, Span<Vector4> destVectors, int count)
             {
                 GuardSpans(sourceColors, nameof(sourceColors), destVectors, nameof(destVectors), count);