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/AlphaAwareImageEncoder.cs

@@ -1,6 +1,8 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+using SixLabors.ImageSharp.Processing.Processors.Quantization;
+
 namespace SixLabors.ImageSharp.Formats;
 
 /// <summary>
@@ -10,6 +12,8 @@ public abstract class AlphaAwareImageEncoder : ImageEncoder
 {
     /// <summary>
     /// Gets or initializes the mode that determines how transparent pixels are handled during encoding.
+    /// This overrides any other settings that may affect the encoding of transparent pixels
+    /// including those passed via <see cref="QuantizerOptions"/>.
     /// </summary>
     public TransparentColorMode TransparentColorMode { get; init; }
 }

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();