Use stackalloc

src/ImageSharp/Formats/Tiff/Compression/Decompressors/T4BitReader.cs

@@ -434,6 +434,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression.Decompressors
         /// </summary>
         /// <param name="nBits">The number of bits to read.</param>
         /// <returns>The value read.</returns>
+        [MethodImpl(InliningOptions.ShortMethod)]
         protected uint ReadValue(int nBits)
         {
             DebugGuard.MustBeGreaterThan(nBits, 0, nameof(nBits));

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/BlackIsZero24TiffColor{TPixel}.cs

@@ -28,10 +28,10 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
         {
             var color = default(TPixel);
             color.FromScaledVector4(Vector4.Zero);
-            byte[] buffer = new byte[4];
+            Span<byte> buffer = stackalloc byte[4];
             int bufferStartIdx = this.isBigEndian ? 1 : 0;
 
-            Span<byte> bufferSpan = buffer.AsSpan(bufferStartIdx);
+            Span<byte> bufferSpan = buffer.Slice(bufferStartIdx);
             int offset = 0;
             for (int y = top; y < top + height; y++)
             {

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/WhiteIsZero24TiffColor{TPixel}.cs

@@ -28,11 +28,11 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
         {
             var color = default(TPixel);
             color.FromScaledVector4(Vector4.Zero);
-            byte[] buffer = new byte[4];
+            Span<byte> buffer = stackalloc byte[4];
             int bufferStartIdx = this.isBigEndian ? 1 : 0;
             const uint maxValue = 0xFFFFFF;
 
-            Span<byte> bufferSpan = buffer.AsSpan(bufferStartIdx);
+            Span<byte> bufferSpan = buffer.Slice(bufferStartIdx);
             int offset = 0;
             for (int y = top; y < top + height; y++)
             {