V4 : Fix GIF, PNG, and WEBP Edge Case Handling

Directory.Build.props

@@ -21,9 +21,8 @@
   <!-- Import the shared global .props file -->
   <Import Project="$(MSBuildThisFileDirectory)shared-infrastructure\msbuild\props\SixLabors.Global.props" />
 
-  <PropertyGroup Condition="$(SIXLABORS_TESTING_PREVIEW) == true">
-    <!-- Workaround various issues bound to implicit language features. -->
-    <LangVersion>preview</LangVersion>
+  <PropertyGroup>
+    <LangVersion>12.0</LangVersion>
   </PropertyGroup>
 
   <!--

src/ImageSharp/Advanced/AotCompilerTools.cs

@@ -138,10 +138,11 @@ private static void Seed<TPixel>()
         AotCompileResamplers<TPixel>();
         AotCompileQuantizers<TPixel>();
         AotCompilePixelSamplingStrategys<TPixel>();
+        AotCompilePixelMaps<TPixel>();
         AotCompileDithers<TPixel>();
         AotCompileMemoryManagers<TPixel>();
 
-        Unsafe.SizeOf<TPixel>();
+        _ = Unsafe.SizeOf<TPixel>();
 
         // TODO: Do the discovery work to figure out what works and what doesn't.
     }
@@ -514,6 +515,20 @@ private static void AotCompilePixelSamplingStrategys<TPixel>()
         default(ExtensivePixelSamplingStrategy).EnumeratePixelRegions(default(ImageFrame<TPixel>));
     }
 
+    /// <summary>
+    /// This method pre-seeds the all <see cref="IColorIndexCache{T}" /> in the AoT compiler.
+    /// </summary>
+    /// <typeparam name="TPixel">The pixel format.</typeparam>
+    [Preserve]
+    private static void AotCompilePixelMaps<TPixel>()
+        where TPixel : unmanaged, IPixel<TPixel>
+    {
+        default(EuclideanPixelMap<TPixel, HybridCache>).GetClosestColor(default, out _);
+        default(EuclideanPixelMap<TPixel, AccurateCache>).GetClosestColor(default, out _);
+        default(EuclideanPixelMap<TPixel, CoarseCache>).GetClosestColor(default, out _);
+        default(EuclideanPixelMap<TPixel, NullCache>).GetClosestColor(default, out _);
+    }
+
     /// <summary>
     /// This method pre-seeds the all <see cref="IDither" /> in the AoT compiler.
     /// </summary>

src/ImageSharp/Common/InlineArray.cs

@@ -0,0 +1,29 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+// <auto-generated />
+
+using System;
+using System.Runtime.CompilerServices;
+
+namespace SixLabors.ImageSharp;
+
+/// <summary>
+/// Represents a safe, fixed sized buffer of 4 elements.
+/// </summary>
+[InlineArray(4)]
+internal struct InlineArray4<T>
+{
+    private T t;
+}
+
+/// <summary>
+/// Represents a safe, fixed sized buffer of 16 elements.
+/// </summary>
+[InlineArray(16)]
+internal struct InlineArray16<T>
+{
+    private T t;
+}
+
+

src/ImageSharp/Common/InlineArray.tt

@@ -0,0 +1,38 @@
+<#@ template debug="false" hostspecific="false" language="C#" #>
+<#@ assembly name="System.Core" #>
+<#@ import namespace="System.Linq" #>
+<#@ import namespace="System.Text" #>
+<#@ import namespace="System.Collections.Generic" #>
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+// <auto-generated />
+
+using System;
+using System.Runtime.CompilerServices;
+
+namespace SixLabors.ImageSharp;
+
+<#GenerateInlineArrays();#>
+
+<#+
+private static int[] Lengths = new int[] {4, 16 };
+
+void GenerateInlineArrays()
+{
+    foreach (int length in Lengths)
+    {
+#>
+/// <summary>
+/// Represents a safe, fixed sized buffer of <#=length#> elements.
+/// </summary>
+[InlineArray(<#=length#>)]
+internal struct InlineArray<#=length#><T>
+{
+    private T t;
+}
+
+<#+
+    }
+}
+#>

src/ImageSharp/Formats/Bmp/BmpEncoderCore.cs

@@ -362,10 +362,13 @@ private void WriteImage<TPixel>(
         ImageFrame<TPixel>? clonedFrame = null;
         try
         {
-            if (EncodingUtilities.ShouldClearTransparentPixels<TPixel>(this.transparentColorMode))
+            // No need to clone when quantizing. The quantizer will do it for us.
+            // TODO: We should really try to avoid the clone entirely.
+            int bpp = this.bitsPerPixel != null ? (int)this.bitsPerPixel : 32;
+            if (bpp > 8 && EncodingUtilities.ShouldReplaceTransparentPixels<TPixel>(this.transparentColorMode))
             {
                 clonedFrame = image.Frames.RootFrame.Clone();
-                EncodingUtilities.ClearTransparentPixels(clonedFrame, Color.Transparent);
+                EncodingUtilities.ReplaceTransparentPixels(clonedFrame);
             }
 
             ImageFrame<TPixel> encodingFrame = clonedFrame ?? image.Frames.RootFrame;

src/ImageSharp/Formats/Bmp/BmpMetadata.cs

@@ -158,6 +158,5 @@ public FormatConnectingMetadata ToFormatConnectingMetadata()
     /// <inheritdoc/>
     public void AfterImageApply<TPixel>(Image<TPixel> destination)
         where TPixel : unmanaged, IPixel<TPixel>
-    {
-    }
+        => this.ColorTable = null;
 }

src/ImageSharp/Formats/Cur/CurFrameMetadata.cs

@@ -104,7 +104,6 @@ public static CurFrameMetadata FromFormatConnectingFrameMetadata(FormatConnectin
             Compression = compression,
             EncodingWidth = ClampEncodingDimension(metadata.EncodingWidth),
             EncodingHeight = ClampEncodingDimension(metadata.EncodingHeight),
-            ColorTable = compression == IconFrameCompression.Bmp ? metadata.ColorTable : null
         };
     }
 
@@ -113,7 +112,6 @@ public FormatConnectingFrameMetadata ToFormatConnectingFrameMetadata()
         => new()
         {
             PixelTypeInfo = this.GetPixelTypeInfo(),
-            ColorTable = this.ColorTable,
             EncodingWidth = this.EncodingWidth,
             EncodingHeight = this.EncodingHeight
         };
@@ -126,6 +124,7 @@ public void AfterFrameApply<TPixel>(ImageFrame<TPixel> source, ImageFrame<TPixel
         float ratioY = destination.Height / (float)source.Height;
         this.EncodingWidth = ScaleEncodingDimension(this.EncodingWidth, destination.Width, ratioX);
         this.EncodingHeight = ScaleEncodingDimension(this.EncodingHeight, destination.Height, ratioY);
+        this.ColorTable = null;
     }
 
     /// <inheritdoc/>

src/ImageSharp/Formats/Cur/CurMetadata.cs

@@ -71,8 +71,7 @@ public static CurMetadata FromFormatConnectingMetadata(FormatConnectingMetadata
         return new CurMetadata
         {
             BmpBitsPerPixel = bbpp,
-            Compression = compression,
-            ColorTable = compression == IconFrameCompression.Bmp ? metadata.ColorTable : null
+            Compression = compression
         };
     }
 
@@ -145,15 +144,13 @@ public FormatConnectingMetadata ToFormatConnectingMetadata()
             EncodingType = this.Compression == IconFrameCompression.Bmp && this.BmpBitsPerPixel <= BmpBitsPerPixel.Bit8
                 ? EncodingType.Lossy
                 : EncodingType.Lossless,
-            PixelTypeInfo = this.GetPixelTypeInfo(),
-            ColorTable = this.ColorTable
+            PixelTypeInfo = this.GetPixelTypeInfo()
         };
 
     /// <inheritdoc/>
     public void AfterImageApply<TPixel>(Image<TPixel> destination)
         where TPixel : unmanaged, IPixel<TPixel>
-    {
-    }
+        => this.ColorTable = null;
 
     /// <inheritdoc/>
     IDeepCloneable IDeepCloneable.DeepClone() => this.DeepClone();

src/ImageSharp/Formats/EncodingUtilities.cs

@@ -3,6 +3,8 @@
 
 using System.Buffers;
 using System.Numerics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 using System.Runtime.Intrinsics;
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;
@@ -14,62 +16,132 @@ namespace SixLabors.ImageSharp.Formats;
 /// </summary>
 internal static class EncodingUtilities
 {
-    public static bool ShouldClearTransparentPixels<TPixel>(TransparentColorMode mode)
+    /// <summary>
+    /// Determines if transparent pixels can be replaced based on the specified color mode and pixel type.
+    /// </summary>
+    /// <typeparam name="TPixel">The type of the pixel.</typeparam>
+    /// <param name="mode">Indicates the color mode used to assess the ability to replace transparent pixels.</param>
+    /// <returns>Returns true if transparent pixels can be replaced; otherwise, false.</returns>
+    public static bool ShouldReplaceTransparentPixels<TPixel>(TransparentColorMode mode)
+        where TPixel : unmanaged, IPixel<TPixel>
+        => mode == TransparentColorMode.Clear && TPixel.GetPixelTypeInfo().AlphaRepresentation == PixelAlphaRepresentation.Unassociated;
+
+    /// <summary>
+    /// Replaces pixels with a transparent alpha component with fully transparent pixels.
+    /// </summary>
+    /// <typeparam name="TPixel">The type of the pixel.</typeparam>
+    /// <param name="frame">The <see cref="ImageFrame{TPixel}"/> where the transparent pixels will be changed.</param>
+    public static void ReplaceTransparentPixels<TPixel>(ImageFrame<TPixel> frame)
         where TPixel : unmanaged, IPixel<TPixel>
-        => mode == TransparentColorMode.Clear &&
-                   TPixel.GetPixelTypeInfo().AlphaRepresentation == PixelAlphaRepresentation.Unassociated;
+        => ReplaceTransparentPixels(frame.Configuration, frame.PixelBuffer);
 
     /// <summary>
-    /// Convert transparent pixels, to pixels represented by <paramref name="color"/>, which can yield
-    /// to better compression in some cases.
+    /// Replaces pixels with a transparent alpha component with fully transparent pixels.
     /// </summary>
     /// <typeparam name="TPixel">The type of the pixel.</typeparam>
-    /// <param name="clone">The cloned <see cref="ImageFrame{TPixel}"/> where the transparent pixels will be changed.</param>
-    /// <param name="color">The color to replace transparent pixels with.</param>
-    public static void ClearTransparentPixels<TPixel>(ImageFrame<TPixel> clone, Color color)
+    /// <param name="configuration">The configuration.</param>
+    /// <param name="buffer">The  <see cref="Buffer2D{TPixel}"/> where the transparent pixels will be changed.</param>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void ReplaceTransparentPixels<TPixel>(Configuration configuration, Buffer2D<TPixel> buffer)
         where TPixel : unmanaged, IPixel<TPixel>
     {
-        Buffer2DRegion<TPixel> buffer = clone.PixelBuffer.GetRegion();
-        ClearTransparentPixels(clone.Configuration, ref buffer, color);
+        Buffer2DRegion<TPixel> region = buffer.GetRegion();
+        ReplaceTransparentPixels(configuration, in region);
     }
 
     /// <summary>
-    /// Convert transparent pixels, to pixels represented by <paramref name="color"/>, which can yield
-    /// to better compression in some cases.
+    /// Replaces pixels with a transparent alpha component with fully transparent pixels.
     /// </summary>
     /// <typeparam name="TPixel">The type of the pixel.</typeparam>
     /// <param name="configuration">The configuration.</param>
-    /// <param name="clone">The cloned <see cref="Buffer2DRegion{T}"/> where the transparent pixels will be changed.</param>
-    /// <param name="color">The color to replace transparent pixels with.</param>
-    public static void ClearTransparentPixels<TPixel>(
+    /// <param name="region">The <see cref="Buffer2DRegion{T}"/> where the transparent pixels will be changed.</param>
+    public static void ReplaceTransparentPixels<TPixel>(
         Configuration configuration,
-        ref Buffer2DRegion<TPixel> clone,
-        Color color)
+        in Buffer2DRegion<TPixel> region)
         where TPixel : unmanaged, IPixel<TPixel>
     {
-        using IMemoryOwner<Vector4> vectors = configuration.MemoryAllocator.Allocate<Vector4>(clone.Width);
+        using IMemoryOwner<Vector4> vectors = configuration.MemoryAllocator.Allocate<Vector4>(region.Width);
         Span<Vector4> vectorsSpan = vectors.GetSpan();
-        Vector4 replacement = color.ToScaledVector4();
-        for (int y = 0; y < clone.Height; y++)
+        for (int y = 0; y < region.Height; y++)
         {
-            Span<TPixel> span = clone.DangerousGetRowSpan(y);
+            Span<TPixel> span = region.DangerousGetRowSpan(y);
             PixelOperations<TPixel>.Instance.ToVector4(configuration, span, vectorsSpan, PixelConversionModifiers.Scale);
-            ClearTransparentPixelRow(vectorsSpan, replacement);
+            ReplaceTransparentPixels(vectorsSpan);
             PixelOperations<TPixel>.Instance.FromVector4Destructive(configuration, vectorsSpan, span, PixelConversionModifiers.Scale);
         }
     }
 
-    private static void ClearTransparentPixelRow(
-        Span<Vector4> vectorsSpan,
-        Vector4 replacement)
+    /// <summary>
+    /// Replaces pixels with a transparent alpha component with fully transparent pixels.
+    /// </summary>
+    /// <param name="source">A span of color vectors that will be checked for transparency and potentially modified.</param>
+    public static void ReplaceTransparentPixels(Span<Vector4> source)
     {
-        if (Vector128.IsHardwareAccelerated)
+        if (Vector512.IsHardwareAccelerated && source.Length >= 4)
+        {
+            Span<Vector512<float>> source512 = MemoryMarshal.Cast<Vector4, Vector512<float>>(source);
+            for (int i = 0; i < source512.Length; i++)
+            {
+                ref Vector512<float> v = ref source512[i];
+
+                // Do `vector < threshold`
+                Vector512<float> mask = Vector512.Equals(v, Vector512<float>.Zero);
+
+                // Replicate the result for W to all elements (is AllBitsSet if the W was 0 and Zero otherwise)
+                mask = Vector512.Shuffle(mask, Vector512.Create(3, 3, 3, 3, 7, 7, 7, 7, 11, 11, 11, 11, 15, 15, 15, 15));
+
+                // Use the mask to select the replacement vector
+                // (replacement & mask) | (v512 & ~mask)
+                v = Vector512.ConditionalSelect(mask, Vector512<float>.Zero, v);
+            }
+
+            int m = Numerics.Modulo4(source.Length);
+            if (m != 0)
+            {
+                for (int i = source.Length - m; i < source.Length; i++)
+                {
+                    if (source[i].W == 0)
+                    {
+                        source[i] = Vector4.Zero;
+                    }
+                }
+            }
+        }
+        else if (Vector256.IsHardwareAccelerated && source.Length >= 2)
         {
-            Vector128<float> replacement128 = replacement.AsVector128();
+            Span<Vector256<float>> source256 = MemoryMarshal.Cast<Vector4, Vector256<float>>(source);
+            for (int i = 0; i < source256.Length; i++)
+            {
+                ref Vector256<float> v = ref source256[i];
+
+                // Do `vector < threshold`
+                Vector256<float> mask = Vector256.Equals(v, Vector256<float>.Zero);
+
+                // Replicate the result for W to all elements (is AllBitsSet if the W was 0 and Zero otherwise)
+                mask = Vector256.Shuffle(mask, Vector256.Create(3, 3, 3, 3, 7, 7, 7, 7));
 
-            for (int i = 0; i < vectorsSpan.Length; i++)
+                // Use the mask to select the replacement vector
+                // (replacement & mask) | (v256 & ~mask)
+                v = Vector256.ConditionalSelect(mask, Vector256<float>.Zero, v);
+            }
+
+            int m = Numerics.Modulo2(source.Length);
+            if (m != 0)
+            {
+                for (int i = source.Length - m; i < source.Length; i++)
+                {
+                    if (source[i].W == 0)
+                    {
+                        source[i] = Vector4.Zero;
+                    }
+                }
+            }
+        }
+        else if (Vector128.IsHardwareAccelerated)
+        {
+            for (int i = 0; i < source.Length; i++)
             {
-                ref Vector4 v = ref vectorsSpan[i];
+                ref Vector4 v = ref source[i];
                 Vector128<float> v128 = v.AsVector128();
 
                 // Do `vector == 0`
@@ -80,16 +152,16 @@ private static void ClearTransparentPixelRow(
 
                 // Use the mask to select the replacement vector
                 // (replacement & mask) | (v128 & ~mask)
-                v = Vector128.ConditionalSelect(mask, replacement128, v128).AsVector4();
+                v = Vector128.ConditionalSelect(mask, Vector128<float>.Zero, v128).AsVector4();
             }
         }
         else
         {
-            for (int i = 0; i < vectorsSpan.Length; i++)
+            for (int i = 0; i < source.Length; i++)
             {
-                if (vectorsSpan[i].W == 0F)
+                if (source[i].W == 0F)
                 {
-                    vectorsSpan[i] = replacement;
+                    source[i] = Vector4.Zero;
                 }
             }
         }

src/ImageSharp/Formats/FormatConnectingFrameMetadata.cs

@@ -15,11 +15,6 @@ public class FormatConnectingFrameMetadata
     /// </summary>
     public PixelTypeInfo? PixelTypeInfo { get; init; }
 
-    /// <summary>
-    /// Gets the frame color table if any.
-    /// </summary>
-    public ReadOnlyMemory<Color>? ColorTable { get; init; }
-
     /// <summary>
     /// Gets the frame color table mode.
     /// </summary>