gif anim palette closest color remap

brendan-duncan · Apr 7, 2024 · 7e8a1f6 · 7e8a1f6
1 parent bf3b302
commit 7e8a1f6
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Showing 2 changed files with 28 additions and 9 deletions.
diff --git a/lib/src/formats/gif/gif_color_map.dart b/lib/src/formats/gif/gif_color_map.dart
@@ -30,15 +30,32 @@ class GifColorMap {
   }
 
   int findColor(num r, num g, num b, num a) {
+    num closestDistance = -1;
+    var closestIndex = -1;
     for (var i = 0; i < numColors; ++i) {
-      if (_palette.getRed(i) == r &&
-          _palette.getGreen(i) == g &&
-          _palette.getBlue(i) == b &&
-          _palette.getAlpha(i) == a) {
+      final pr = _palette.getRed(i);
+      final pg = _palette.getGreen(i);
+      final pb = _palette.getBlue(i);
+      final pa = _palette.getAlpha(i);
+      if (pr == r && pg == g && pb == b && pa == a) {
         return i;
       }
+      final dr = r - pr;
+      final dg = g - pg;
+      final db = b - pb;
+      final da = a - pa;
+      final d2 = (dr * dr) + (dg * dg) + (db * db) + (da * da);
+      if (closestIndex == -1) {
+        closestIndex = i;
+        closestDistance = d2;
+      } else {
+        if (d2 < closestDistance) {
+          closestIndex = i;
+          closestDistance = d2;
+        }
+      }
     }
-    return -1;
+    return closestIndex;
   }
 
   int red(int color) => _palette.getRed(color) as int;

diff --git a/lib/src/formats/gif_decoder.dart b/lib/src/formats/gif_decoder.dart
@@ -217,14 +217,16 @@ class GifDecoder extends Decoder {
       if (frame.disposal == 2) {
         nextImage.clear(colorMap.color(info!.backgroundColor!.r as int));
       } else if (frame.disposal != 3) {
-        if (frame.x != 0 || frame.y != 0 || frame.width != lastImage.width ||
+        if (frame.x != 0 ||
+            frame.y != 0 ||
+            frame.width != lastImage.width ||
             frame.height != lastImage.height) {
           if (frame.colorMap != null) {
             final lp = lastImage.palette!;
-            final remapColors = <int,int>{};
+            final remapColors = <int, int>{};
             for (var ci = 0; ci < colorMap.numColors; ++ci) {
-              final nc = colorMap.findColor(
-                  lp.getRed(ci), lp.getGreen(ci), lp.getBlue(ci), lp.getAlpha(ci));
+              final nc = colorMap.findColor(lp.getRed(ci), lp.getGreen(ci),
+                  lp.getBlue(ci), lp.getAlpha(ci));
               remapColors[ci] = nc;
             }