3.2 DitheringRegistry

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

IMPLEMENTATION.md

@@ -100,7 +100,7 @@ Each type lives in `src/FrameProcessor/Domain/`. Tests in `tests/FrameProcessor.
 - `static ReadOnlyMemory<Color> BuildDisplay(IReadOnlyList<PaletteEntry>)` and `BuildDevice(...)`.
 - **Tests:** `PaletteFactoryTests` — count, ordering preserved.
 
-### [ ] 3.2 `DitheringRegistry`
+### [x] 3.2 `DitheringRegistry`
 - `IReadOnlyDictionary<DitherAlgorithm, IDither>` mapping each enum to the corresponding ImageSharp `KnownDitherings.*`.
 
 ### [ ] 3.3 `IImagePipeline` + `ImagePipeline`

src/FrameProcessor/ImagePipeline/DitheringRegistry.cs

@@ -0,0 +1,21 @@
+using FrameProcessor.Domain;
+using SixLabors.ImageSharp.Processing;
+using SixLabors.ImageSharp.Processing.Processors.Dithering;
+
+namespace FrameProcessor.ImagePipeline;
+
+/// <summary>
+/// Maps each <see cref="DitherAlgorithm"/> to the corresponding ImageSharp <see cref="IDither"/>
+/// instance from <see cref="KnownDitherings"/>.
+/// </summary>
+public static class DitheringRegistry
+{
+    public static IReadOnlyDictionary<DitherAlgorithm, IDither> All { get; } =
+        new Dictionary<DitherAlgorithm, IDither>
+        {
+            [DitherAlgorithm.FloydSteinberg] = KnownDitherings.FloydSteinberg,
+            [DitherAlgorithm.Atkinson] = KnownDitherings.Atkinson,
+            [DitherAlgorithm.Stucki] = KnownDitherings.Stucki,
+            [DitherAlgorithm.Jarvis] = KnownDitherings.JarvisJudiceNinke,
+        };
+}