Simplify API and clone options.

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/Gif/GifEncoderCore.cs

@@ -150,10 +150,7 @@ internal sealed class GifEncoderCore
         TransparentColorMode mode = this.transparentColorMode;
         QuantizerOptions options = this.quantizer.Options.DeepClone(o => o.TransparentColorMode = mode);
 
-        // Quantize the first frame. Checking to see whether we can clear the transparent pixels
-        // to allow for a smaller color palette and encoded result.
-        // TODO: What should we use as the background color here?
-        Color background = Color.Transparent;
+        // Quantize the first frame.
         using (IQuantizer<TPixel> frameQuantizer = this.quantizer.CreatePixelSpecificQuantizer<TPixel>(this.configuration, options))
         {
             IPixelSamplingStrategy strategy = this.pixelSamplingStrategy;
@@ -163,12 +160,12 @@ internal sealed class GifEncoderCore
             {
                 if (useGlobalTable)
                 {
-                    frameQuantizer.BuildPalette(mode, strategy, image);
+                    frameQuantizer.BuildPalette(strategy, image);
                     quantized = frameQuantizer.QuantizeFrame(encodingFrame, image.Bounds);
                 }
                 else
                 {
-                    frameQuantizer.BuildPalette(mode, strategy, encodingFrame);
+                    frameQuantizer.BuildPalette(strategy, encodingFrame);
                     quantized = frameQuantizer.QuantizeFrame(encodingFrame, encodingFrame.Bounds);
                 }
             }
@@ -176,13 +173,14 @@ internal sealed class GifEncoderCore
             {
                 quantized = this.QuantizeAdditionalFrameAndUpdateMetadata(
                     encodingFrame,
+                    options,
                     encodingFrame.Bounds,
                     frameMetadata,
                     true,
                     default,
                     false,
                     frameMetadata.HasTransparency ? frameMetadata.TransparencyIndex : -1,
-                    background);
+                    Color.Transparent);
             }
         }
 
@@ -197,6 +195,7 @@ internal sealed class GifEncoderCore
             frameMetadata.TransparencyIndex = ClampIndex(derivedTransparencyIndex);
         }
 
+        // TODO: We should be checking the metadata here also I think?
         if (!TryGetBackgroundIndex(quantized, this.backgroundColor, out byte backgroundIndex))
         {
             backgroundIndex = derivedTransparencyIndex >= 0
@@ -235,6 +234,7 @@ internal sealed class GifEncoderCore
             this.EncodeAdditionalFrames(
                 stream,
                 image,
+                options,
                 globalPalette,
                 derivedTransparencyIndex,
                 frameMetadata.DisposalMode,
@@ -264,6 +264,7 @@ internal sealed class GifEncoderCore
     private void EncodeAdditionalFrames<TPixel>(
         Stream stream,
         Image<TPixel> image,
+        QuantizerOptions options,
         ReadOnlyMemory<TPixel> globalPalette,
         int globalTransparencyIndex,
         FrameDisposalMode previousDisposalMode,
@@ -301,7 +302,7 @@ internal sealed class GifEncoderCore
                     // The palette quantizer can reuse the same global pixel map across multiple frames since the palette is unchanging.
                     // This allows a reduction of memory usage across multi-frame gifs using a global palette
                     // and also allows use to reuse the cache from previous runs.
-                    globalPaletteQuantizer = new(this.configuration, this.quantizer!.Options, globalPalette);
+                    globalPaletteQuantizer = new(this.configuration, options, globalPalette);
                     hasGlobalPaletteQuantizer = true;
                 }
 
@@ -311,6 +312,7 @@ internal sealed class GifEncoderCore
                     currentFrame,
                     nextFrame,
                     encodingFrame,
+                    options,
                     useLocal,
                     gifMetadata,
                     globalPaletteQuantizer,
@@ -361,6 +363,7 @@ internal sealed class GifEncoderCore
         ImageFrame<TPixel> currentFrame,
         ImageFrame<TPixel>? nextFrame,
         ImageFrame<TPixel> encodingFrame,
+        QuantizerOptions options,
         bool useLocal,
         GifFrameMetadata metadata,
         PaletteQuantizer<TPixel> globalPaletteQuantizer,
@@ -392,6 +395,7 @@ internal sealed class GifEncoderCore
 
         using IndexedImageFrame<TPixel> quantized = this.QuantizeAdditionalFrameAndUpdateMetadata(
                 encodingFrame,
+                options,
                 bounds,
                 metadata,
                 useLocal,
@@ -416,6 +420,7 @@ internal sealed class GifEncoderCore
 
     private IndexedImageFrame<TPixel> QuantizeAdditionalFrameAndUpdateMetadata<TPixel>(
         ImageFrame<TPixel> encodingFrame,
+        QuantizerOptions options,
         Rectangle bounds,
         GifFrameMetadata metadata,
         bool useLocal,
@@ -446,7 +451,12 @@ internal sealed class GifEncoderCore
                         transparencyIndex = palette.Length;
                         metadata.TransparencyIndex = ClampIndex(transparencyIndex);
 
-                        PaletteQuantizer quantizer = new(palette, new() { Dither = null }, transparencyIndex, transparentColor);
+                        QuantizerOptions paletteOptions = options.DeepClone(o =>
+                        {
+                            o.MaxColors = palette.Length;
+                            o.Dither = null;
+                        });
+                        PaletteQuantizer quantizer = new(palette, paletteOptions, transparencyIndex, transparentColor);
                         using IQuantizer<TPixel> frameQuantizer = quantizer.CreatePixelSpecificQuantizer<TPixel>(this.configuration, quantizer.Options);
                         quantized = frameQuantizer.BuildPaletteAndQuantizeFrame(encodingFrame, bounds);
                     }
@@ -454,7 +464,7 @@ internal sealed class GifEncoderCore
                     {
                         // We must quantize the frame to generate a local color table.
                         IQuantizer quantizer = this.hasQuantizer ? this.quantizer! : FallbackQuantizer;
-                        using IQuantizer<TPixel> frameQuantizer = quantizer.CreatePixelSpecificQuantizer<TPixel>(this.configuration, quantizer.Options);
+                        using IQuantizer<TPixel> frameQuantizer = quantizer.CreatePixelSpecificQuantizer<TPixel>(this.configuration, options);
                         quantized = frameQuantizer.BuildPaletteAndQuantizeFrame(encodingFrame, bounds);
 
                         // The transparency index derived by the quantizer will differ from the index
@@ -466,7 +476,12 @@ internal sealed class GifEncoderCore
                 else
                 {
                     // Just use the local palette.
-                    PaletteQuantizer quantizer = new(palette, new() { Dither = null }, transparencyIndex, transparentColor);
+                    QuantizerOptions paletteOptions = options.DeepClone(o =>
+                    {
+                        o.MaxColors = palette.Length;
+                        o.Dither = null;
+                    });
+                    PaletteQuantizer quantizer = new(palette, paletteOptions, transparencyIndex, transparentColor);
                     using IQuantizer<TPixel> frameQuantizer = quantizer.CreatePixelSpecificQuantizer<TPixel>(this.configuration, quantizer.Options);
                     quantized = frameQuantizer.BuildPaletteAndQuantizeFrame(encodingFrame, bounds);
                 }
@@ -475,7 +490,7 @@ internal sealed class GifEncoderCore
             {
                 // We must quantize the frame to generate a local color table.
                 IQuantizer quantizer = this.hasQuantizer ? this.quantizer! : FallbackQuantizer;
-                using IQuantizer<TPixel> frameQuantizer = quantizer.CreatePixelSpecificQuantizer<TPixel>(this.configuration, quantizer.Options);
+                using IQuantizer<TPixel> frameQuantizer = quantizer.CreatePixelSpecificQuantizer<TPixel>(this.configuration, options);
                 quantized = frameQuantizer.BuildPaletteAndQuantizeFrame(encodingFrame, bounds);
 
                 // The transparency index derived by the quantizer might differ from the index

src/ImageSharp/Formats/Png/PngEncoderCore.cs

@@ -1574,13 +1574,21 @@ internal sealed class PngEncoderCore : IDisposable
             {
                 // We can use the color data from the decoded metadata here.
                 // We avoid dithering by default to preserve the original colors.
-                this.quantizer = new PaletteQuantizer(metadata.ColorTable.Value, new() { Dither = null });
+                QuantizerOptions options = new() { Dither = null, TransparentColorMode = encoder.TransparentColorMode };
+                this.quantizer = new PaletteQuantizer(metadata.ColorTable.Value, options);
             }
             else
             {
                 // Don't use the default transparency threshold for quantization as PNG can handle multiple transparent colors.
                 // We choose a value that is close to zero so that edge cases causes by lower bit depths for the alpha channel are handled correctly.
-                this.quantizer = new WuQuantizer(new QuantizerOptions { TransparencyThreshold = 0, MaxColors = ColorNumerics.GetColorCountForBitDepth(bitDepth) });
+                QuantizerOptions options = new()
+                {
+                    TransparencyThreshold = 0,
+                    MaxColors = ColorNumerics.GetColorCountForBitDepth(bitDepth),
+                    TransparentColorMode = encoder.TransparentColorMode
+                };
+
+                this.quantizer = new WuQuantizer(options);
             }
         }
 
@@ -1604,7 +1612,6 @@ internal sealed class PngEncoderCore : IDisposable
         }
 
         frameQuantizer.BuildPalette(
-            encoder.TransparentColorMode,
             encoder.PixelSamplingStrategy,
             image);
 

src/ImageSharp/Formats/TransparentColorMode.cs

@@ -4,7 +4,7 @@
 namespace SixLabors.ImageSharp.Formats;
 
 /// <summary>
-/// Specifies how transparent pixels should be handled during encoding and quantization.
+/// Specifies how pixels with transparent alpha components should be handled during encoding and quantization.
 /// </summary>
 public enum TransparentColorMode
 {

src/ImageSharp/Processing/Processors/Quantization/IQuantizer{TPixel}.cs

@@ -1,7 +1,6 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
-using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;
 
@@ -36,37 +35,13 @@ public interface IQuantizer<TPixel> : IDisposable
     /// Adds colors to the quantized palette from the given pixel source.
     /// </summary>
     /// <param name="pixelRegion">The <see cref="Buffer2DRegion{T}"/> of source pixels to register.</param>
-    public void AddPaletteColors(in Buffer2DRegion<TPixel> pixelRegion)
-        => this.AddPaletteColors(pixelRegion, TransparentColorMode.Preserve);
-
-    /// <summary>
-    /// Adds colors to the quantized palette from the given pixel source.
-    /// </summary>
-    /// <param name="pixelRegion">The <see cref="Buffer2DRegion{T}"/> of source pixels to register.</param>
-    /// <param name="mode">The <see cref="TransparentColorMode"/> to use when adding colors to the palette.</param>
-    public void AddPaletteColors(in Buffer2DRegion<TPixel> pixelRegion, TransparentColorMode mode);
-
-    /// <summary>
-    /// Quantizes an image frame and return the resulting output pixels.
-    /// </summary>
-    /// <param name="source">The source image frame to quantize.</param>
-    /// <param name="bounds">The bounds within the frame to quantize.</param>
-    /// <returns>
-    /// A <see cref="IndexedImageFrame{TPixel}"/> representing a quantized version of the source frame pixels.
-    /// </returns>
-    /// <remarks>
-    /// Only executes the second (quantization) step. The palette has to be built by calling <see cref="AddPaletteColors(in Buffer2DRegion{TPixel})"/>.
-    /// To run both steps, use <see cref="QuantizerUtilities.BuildPaletteAndQuantizeFrame{TPixel}(IQuantizer{TPixel}, ImageFrame{TPixel}, Rectangle)"/>.
-    /// </remarks>
-    public IndexedImageFrame<TPixel> QuantizeFrame(ImageFrame<TPixel> source, Rectangle bounds)
-        => this.QuantizeFrame(source, bounds, TransparentColorMode.Preserve);
+    public void AddPaletteColors(in Buffer2DRegion<TPixel> pixelRegion);
 
     /// <summary>
     /// Quantizes an image frame and return the resulting output pixels.
     /// </summary>
     /// <param name="source">The source image frame to quantize.</param>
     /// <param name="bounds">The bounds within the frame to quantize.</param>
-    /// <param name="mode">The <see cref="TransparentColorMode"/> to use when quantizing the frame.</param>
     /// <returns>
     /// A <see cref="IndexedImageFrame{TPixel}"/> representing a quantized version of the source frame pixels.
     /// </returns>
@@ -74,7 +49,7 @@ public interface IQuantizer<TPixel> : IDisposable
     /// Only executes the second (quantization) step. The palette has to be built by calling <see cref="AddPaletteColors(in Buffer2DRegion{TPixel})"/>.
     /// To run both steps, use <see cref="QuantizerUtilities.BuildPaletteAndQuantizeFrame{TPixel}(IQuantizer{TPixel}, ImageFrame{TPixel}, Rectangle)"/>.
     /// </remarks>
-    public IndexedImageFrame<TPixel> QuantizeFrame(ImageFrame<TPixel> source, Rectangle bounds, TransparentColorMode mode);
+    public IndexedImageFrame<TPixel> QuantizeFrame(ImageFrame<TPixel> source, Rectangle bounds);
 
     /// <summary>
     /// Returns the index and color from the quantized palette corresponding to the given color.

src/ImageSharp/Processing/Processors/Quantization/IQuantizingPixelRowDelegate{TPixel}.cs

@@ -1,7 +1,6 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
-using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.PixelFormats;
 
 namespace SixLabors.ImageSharp.Processing.Processors.Quantization;
@@ -13,11 +12,6 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization;
 internal interface IQuantizingPixelRowDelegate<TPixel>
     where TPixel : unmanaged, IPixel<TPixel>
 {
-    /// <summary>
-    /// Gets the transparent color mode to use when adding colors to the palette.
-    /// </summary>
-    public TransparentColorMode TransparentColorMode { get; }
-
     /// <summary>
     /// Processes a row of pixels for quantization.
     /// </summary>

src/ImageSharp/Processing/Processors/Quantization/OctreeQuantizer{TPixel}.cs

@@ -6,7 +6,6 @@ using System.Diagnostics.CodeAnalysis;
 using System.Numerics;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
-using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;
 
@@ -75,9 +74,9 @@ public struct OctreeQuantizer<TPixel> : IQuantizer<TPixel>
     }
 
     /// <inheritdoc/>
-    public readonly void AddPaletteColors(in Buffer2DRegion<TPixel> pixelRegion, TransparentColorMode mode)
+    public readonly void AddPaletteColors(in Buffer2DRegion<TPixel> pixelRegion)
     {
-        PixelRowDelegate pixelRowDelegate = new(this.octree, mode);
+        PixelRowDelegate pixelRowDelegate = new(this.octree);
         QuantizerUtilities.AddPaletteColors<OctreeQuantizer<TPixel>, TPixel, Rgba32, PixelRowDelegate>(
             ref Unsafe.AsRef(in this),
             in pixelRegion,
@@ -103,12 +102,7 @@ public struct OctreeQuantizer<TPixel> : IQuantizer<TPixel>
     /// <inheritdoc/>
     [MethodImpl(InliningOptions.ShortMethod)]
     public readonly IndexedImageFrame<TPixel> QuantizeFrame(ImageFrame<TPixel> source, Rectangle bounds)
-        => this.QuantizeFrame(source, bounds, TransparentColorMode.Preserve);
-
-    /// <inheritdoc/>
-    [MethodImpl(InliningOptions.ShortMethod)]
-    public readonly IndexedImageFrame<TPixel> QuantizeFrame(ImageFrame<TPixel> source, Rectangle bounds, TransparentColorMode mode)
-        => QuantizerUtilities.QuantizeFrame(ref Unsafe.AsRef(in this), source, bounds, mode);
+        => QuantizerUtilities.QuantizeFrame(ref Unsafe.AsRef(in this), source, bounds);
 
     /// <inheritdoc/>
     [MethodImpl(InliningOptions.ShortMethod)]
@@ -146,13 +140,7 @@ public struct OctreeQuantizer<TPixel> : IQuantizer<TPixel>
     {
         private readonly Octree octree;
 
-        public PixelRowDelegate(Octree octree, TransparentColorMode mode)
-        {
-            this.octree = octree;
-            this.TransparentColorMode = mode;
-        }
-
-        public TransparentColorMode TransparentColorMode { get; }
+        public PixelRowDelegate(Octree octree) => this.octree = octree;
 
         public void Invoke(ReadOnlySpan<Rgba32> row, int rowIndex) => this.octree.AddColors(row);
     }

src/ImageSharp/Processing/Processors/Quantization/PaletteQuantizer{TPixel}.cs

@@ -3,7 +3,6 @@
 
 using System.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;
-using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;
 
@@ -76,29 +75,18 @@ internal struct PaletteQuantizer<TPixel> : IQuantizer<TPixel>
     /// <inheritdoc/>
     [MethodImpl(InliningOptions.ShortMethod)]
     public readonly void AddPaletteColors(in Buffer2DRegion<TPixel> pixelRegion)
-        => this.AddPaletteColors(in pixelRegion, TransparentColorMode.Preserve);
-
-    /// <inheritdoc/>
-    [MethodImpl(InliningOptions.ShortMethod)]
-    public readonly void AddPaletteColors(in Buffer2DRegion<TPixel> pixelRegion, TransparentColorMode mode)
     {
     }
 
     /// <inheritdoc/>
     [MethodImpl(InliningOptions.ShortMethod)]
     public readonly IndexedImageFrame<TPixel> QuantizeFrame(ImageFrame<TPixel> source, Rectangle bounds)
-        => this.QuantizeFrame(source, bounds, TransparentColorMode.Preserve);
-
-    /// <inheritdoc/>
-    [MethodImpl(InliningOptions.ShortMethod)]
-    public readonly IndexedImageFrame<TPixel> QuantizeFrame(ImageFrame<TPixel> source, Rectangle bounds, TransparentColorMode mode)
-        => QuantizerUtilities.QuantizeFrame(ref Unsafe.AsRef(in this), source, bounds, mode);
+        => QuantizerUtilities.QuantizeFrame(ref Unsafe.AsRef(in this), source, bounds);
 
     /// <inheritdoc/>
     [MethodImpl(InliningOptions.ShortMethod)]
     public readonly byte GetQuantizedColor(TPixel color, out TPixel match)
     {
-        // TODO: We need to use thesholding here.
         if (this.transparencyIndex >= 0 && color.Equals(this.transparentColor))
         {
             match = this.transparentColor;

src/ImageSharp/Processing/Processors/Quantization/QuantizerOptions.cs

@@ -81,7 +81,8 @@ public class QuantizerOptions : IDeepCloneable<QuantizerOptions>
     }
 
     /// <summary>
-    /// Gets or sets the transparent color mode used for handling transparent colors.
+    /// Gets or sets the transparent color mode used for handling transparent colors
+    /// when not using thresholding.
     /// Defaults to <see cref="TransparentColorMode.Preserve"/>.
     /// </summary>
     public TransparentColorMode TransparentColorMode { get; set; } = TransparentColorMode.Preserve;

src/ImageSharp/Processing/Processors/Quantization/QuantizerUtilities.cs

@@ -18,7 +18,13 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization;
 /// </summary>
 public static class QuantizerUtilities
 {
-    internal static QuantizerOptions DeepClone(this QuantizerOptions options, Action<QuantizerOptions>? mutate)
+    /// <summary>
+    /// Performs a deep clone the <see cref="QuantizerOptions"/> instance and optionally mutates the clone.
+    /// </summary>
+    /// <param name="options">The <see cref="QuantizerOptions"/> instance to clone.</param>
+    /// <param name="mutate">An optional delegate to mutate the cloned instance.</param>
+    /// <returns>The cloned <see cref="QuantizerOptions"/> instance.</returns>
+    public static QuantizerOptions DeepClone(this QuantizerOptions options, Action<QuantizerOptions>? mutate)
     {
         QuantizerOptions clone = options.DeepClone();
         mutate?.Invoke(clone);
@@ -170,29 +176,6 @@ public static class QuantizerUtilities
         ImageFrame<TPixel> source,
         Rectangle bounds)
         where TPixel : unmanaged, IPixel<TPixel>
-        => BuildPaletteAndQuantizeFrame(
-            quantizer,
-            source,
-            bounds,
-            TransparentColorMode.Preserve);
-
-    /// <summary>
-    /// Execute both steps of the quantization.
-    /// </summary>
-    /// <param name="quantizer">The pixel specific quantizer.</param>
-    /// <param name="source">The source image frame to quantize.</param>
-    /// <param name="bounds">The bounds within the frame to quantize.</param>
-    /// <param name="mode">The transparent color mode.</param>
-    /// <typeparam name="TPixel">The pixel type.</typeparam>
-    /// <returns>
-    /// A <see cref="IndexedImageFrame{TPixel}"/> representing a quantized version of the source frame pixels.
-    /// </returns>
-    public static IndexedImageFrame<TPixel> BuildPaletteAndQuantizeFrame<TPixel>(
-        this IQuantizer<TPixel> quantizer,
-        ImageFrame<TPixel> source,
-        Rectangle bounds,
-        TransparentColorMode mode)
-        where TPixel : unmanaged, IPixel<TPixel>
     {
         Guard.NotNull(quantizer, nameof(quantizer));
         Guard.NotNull(source, nameof(source));
@@ -200,7 +183,7 @@ public static class QuantizerUtilities
         Rectangle interest = Rectangle.Intersect(source.Bounds, bounds);
         Buffer2DRegion<TPixel> region = source.PixelBuffer.GetRegion(interest);
 
-        quantizer.AddPaletteColors(in region, mode);
+        quantizer.AddPaletteColors(in region);
         return quantizer.QuantizeFrame(source, bounds);
     }
 
@@ -212,15 +195,13 @@ public static class QuantizerUtilities
     /// <param name="quantizer">The pixel specific quantizer.</param>
     /// <param name="source">The source image frame to quantize.</param>
     /// <param name="bounds">The bounds within the frame to quantize.</param>
-    /// <param name="mode">The transparent color mode.</param>
     /// <returns>
     /// A <see cref="IndexedImageFrame{TPixel}"/> representing a quantized version of the source frame pixels.
     /// </returns>
     public static IndexedImageFrame<TPixel> QuantizeFrame<TFrameQuantizer, TPixel>(
         ref TFrameQuantizer quantizer,
         ImageFrame<TPixel> source,
-        Rectangle bounds,
-        TransparentColorMode mode)
+        Rectangle bounds)
         where TFrameQuantizer : struct, IQuantizer<TPixel>
         where TPixel : unmanaged, IPixel<TPixel>
     {
@@ -235,13 +216,13 @@ public static class QuantizerUtilities
 
         if (quantizer.Options.Dither is null)
         {
-            SecondPass(ref quantizer, source, destination, interest, mode);
+            SecondPass(ref quantizer, source, destination, interest);
         }
         else
         {
             // We clone the image as we don't want to alter the original via error diffusion based dithering.
             using ImageFrame<TPixel> clone = source.Clone();
-            SecondPass(ref quantizer, clone, destination, interest, mode);
+            SecondPass(ref quantizer, clone, destination, interest);
         }
 
         return destination;
@@ -259,29 +240,10 @@ public static class QuantizerUtilities
         IPixelSamplingStrategy pixelSamplingStrategy,
         Image<TPixel> source)
         where TPixel : unmanaged, IPixel<TPixel>
-        => quantizer.BuildPalette(
-            TransparentColorMode.Preserve,
-            pixelSamplingStrategy,
-            source);
-
-    /// <summary>
-    /// Adds colors to the quantized palette from the given pixel regions.
-    /// </summary>
-    /// <typeparam name="TPixel">The pixel format.</typeparam>
-    /// <param name="quantizer">The pixel specific quantizer.</param>
-    /// <param name="mode">The transparent color mode.</param>
-    /// <param name="pixelSamplingStrategy">The pixel sampling strategy.</param>
-    /// <param name="source">The source image to sample from.</param>
-    public static void BuildPalette<TPixel>(
-        this IQuantizer<TPixel> quantizer,
-        TransparentColorMode mode,
-        IPixelSamplingStrategy pixelSamplingStrategy,
-        Image<TPixel> source)
-        where TPixel : unmanaged, IPixel<TPixel>
     {
         foreach (Buffer2DRegion<TPixel> region in pixelSamplingStrategy.EnumeratePixelRegions(source))
         {
-            quantizer.AddPaletteColors(in region, mode);
+            quantizer.AddPaletteColors(in region);
         }
     }
 
@@ -297,29 +259,10 @@ public static class QuantizerUtilities
         IPixelSamplingStrategy pixelSamplingStrategy,
         ImageFrame<TPixel> source)
         where TPixel : unmanaged, IPixel<TPixel>
-        => quantizer.BuildPalette(
-            TransparentColorMode.Preserve,
-            pixelSamplingStrategy,
-            source);
-
-    /// <summary>
-    /// Adds colors to the quantized palette from the given pixel regions.
-    /// </summary>
-    /// <typeparam name="TPixel">The pixel format.</typeparam>
-    /// <param name="quantizer">The pixel specific quantizer.</param>
-    /// <param name="mode">The transparent color mode.</param>
-    /// <param name="pixelSamplingStrategy">The pixel sampling strategy.</param>
-    /// <param name="source">The source image frame to sample from.</param>
-    public static void BuildPalette<TPixel>(
-        this IQuantizer<TPixel> quantizer,
-        TransparentColorMode mode,
-        IPixelSamplingStrategy pixelSamplingStrategy,
-        ImageFrame<TPixel> source)
-        where TPixel : unmanaged, IPixel<TPixel>
     {
         foreach (Buffer2DRegion<TPixel> region in pixelSamplingStrategy.EnumeratePixelRegions(source))
         {
-            quantizer.AddPaletteColors(in region, mode);
+            quantizer.AddPaletteColors(in region);
         }
     }
 
@@ -340,7 +283,7 @@ public static class QuantizerUtilities
         Span<TPixel2> delegateRow = delegateRowOwner.Memory.Span;
 
         bool replaceByThreshold = ShouldReplacePixelsByAlphaThreshold<TPixel>(threshold);
-        bool replaceTransparent = EncodingUtilities.ShouldReplaceTransparentPixels<TPixel>(rowDelegate.TransparentColorMode);
+        bool replaceTransparent = EncodingUtilities.ShouldReplaceTransparentPixels<TPixel>(mode);
 
         if (replaceByThreshold || replaceTransparent)
         {
@@ -389,13 +332,14 @@ public static class QuantizerUtilities
         ref TFrameQuantizer quantizer,
         ImageFrame<TPixel> source,
         IndexedImageFrame<TPixel> destination,
-        Rectangle bounds,
-        TransparentColorMode mode)
+        Rectangle bounds)
         where TFrameQuantizer : struct, IQuantizer<TPixel>
         where TPixel : unmanaged, IPixel<TPixel>
     {
         float threshold = quantizer.Options.TransparencyThreshold;
         bool replaceByThreshold = ShouldReplacePixelsByAlphaThreshold<TPixel>(threshold);
+
+        TransparentColorMode mode = quantizer.Options.TransparentColorMode;
         bool replaceTransparent = EncodingUtilities.ShouldReplaceTransparentPixels<TPixel>(mode);
 
         IDither? dither = quantizer.Options.Dither;

src/ImageSharp/Processing/Processors/Quantization/WuQuantizer{TPixel}.cs

@@ -6,7 +6,6 @@ using System.Diagnostics.CodeAnalysis;
 using System.Numerics;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
-using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;
 
@@ -107,9 +106,9 @@ internal struct WuQuantizer<TPixel> : IQuantizer<TPixel>
     }
 
     /// <inheritdoc/>
-    public readonly void AddPaletteColors(in Buffer2DRegion<TPixel> pixelRegion, TransparentColorMode mode)
+    public readonly void AddPaletteColors(in Buffer2DRegion<TPixel> pixelRegion)
     {
-        PixelRowDelegate pixelRowDelegate = new(ref Unsafe.AsRef(in this), mode);
+        PixelRowDelegate pixelRowDelegate = new(ref Unsafe.AsRef(in this));
         QuantizerUtilities.AddPaletteColors<WuQuantizer<TPixel>, TPixel, Rgba32, PixelRowDelegate>(
             ref Unsafe.AsRef(in this),
             in pixelRegion,
@@ -162,12 +161,7 @@ internal struct WuQuantizer<TPixel> : IQuantizer<TPixel>
     /// <inheritdoc/>
     [MethodImpl(InliningOptions.ShortMethod)]
     public readonly IndexedImageFrame<TPixel> QuantizeFrame(ImageFrame<TPixel> source, Rectangle bounds)
-        => this.QuantizeFrame(source, bounds, TransparentColorMode.Preserve);
-
-    /// <inheritdoc/>
-    [MethodImpl(InliningOptions.ShortMethod)]
-    public readonly IndexedImageFrame<TPixel> QuantizeFrame(ImageFrame<TPixel> source, Rectangle bounds, TransparentColorMode mode)
-        => QuantizerUtilities.QuantizeFrame(ref Unsafe.AsRef(in this), source, bounds, mode);
+        => QuantizerUtilities.QuantizeFrame(ref Unsafe.AsRef(in this), source, bounds);
 
     /// <inheritdoc/>
     public readonly byte GetQuantizedColor(TPixel color, out TPixel match)
@@ -891,13 +885,7 @@ internal struct WuQuantizer<TPixel> : IQuantizer<TPixel>
     {
         private readonly WuQuantizer<TPixel> quantizer;
 
-        public PixelRowDelegate(ref WuQuantizer<TPixel> quantizer, TransparentColorMode mode)
-        {
-            this.quantizer = quantizer;
-            this.TransparentColorMode = mode;
-        }
-
-        public TransparentColorMode TransparentColorMode { get; }
+        public PixelRowDelegate(ref WuQuantizer<TPixel> quantizer) => this.quantizer = quantizer;
 
         public void Invoke(ReadOnlySpan<Rgba32> row, int rowIndex) => this.quantizer.Build3DHistogram(row);
     }