Этап 4

Minint.Core/Services/Impl/PaletteService.cs

@@ -0,0 +1,77 @@
+using Minint.Core.Models;
+
+namespace Minint.Core.Services.Impl;
+
+public sealed class PaletteService : IPaletteService
+{
+    public int FindColor(MinintDocument document, RgbaColor color)
+    {
+        var palette = document.Palette;
+        for (int i = 0; i < palette.Count; i++)
+        {
+            if (palette[i] == color)
+                return i;
+        }
+        return -1;
+    }
+
+    public int EnsureColor(MinintDocument document, RgbaColor color)
+    {
+        int idx = FindColor(document, color);
+        if (idx >= 0)
+            return idx;
+
+        idx = document.Palette.Count;
+        document.Palette.Add(color);
+        return idx;
+    }
+
+    public void CompactPalette(MinintDocument document)
+    {
+        var palette = document.Palette;
+        if (palette.Count <= 1)
+            return;
+
+        // 1. Collect indices actually used across all layers
+        var usedIndices = new HashSet<int> { 0 }; // always keep transparent
+        foreach (var layer in document.Layers)
+        {
+            foreach (int idx in layer.Pixels)
+                usedIndices.Add(idx);
+        }
+
+        // 2. Build new palette and old→new mapping
+        var oldToNew = new int[palette.Count];
+        var newPalette = new List<RgbaColor>(usedIndices.Count);
+
+        // Index 0 (transparent) stays at 0
+        newPalette.Add(palette[0]);
+        oldToNew[0] = 0;
+
+        for (int i = 1; i < palette.Count; i++)
+        {
+            if (usedIndices.Contains(i))
+            {
+                oldToNew[i] = newPalette.Count;
+                newPalette.Add(palette[i]);
+            }
+            // unused indices don't get a mapping — they'll never be looked up
+        }
+
+        // 3. If nothing was removed, skip the remap
+        if (newPalette.Count == palette.Count)
+            return;
+
+        // 4. Replace palette
+        palette.Clear();
+        palette.AddRange(newPalette);
+
+        // 5. Remap all pixel arrays
+        foreach (var layer in document.Layers)
+        {
+            var px = layer.Pixels;
+            for (int i = 0; i < px.Length; i++)
+                px[i] = oldToNew[px[i]];
+        }
+    }
+}