2 channel images map to 4 channe

brendan-duncan · Jan 15, 2024 · 9f39c25 · 9f39c25
1 parent e1892ee
commit 9f39c25
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Showing 4 changed files with 55 additions and 20 deletions.
diff --git a/lib/src/image/pixel_uint8.dart b/lib/src/image/pixel_uint8.dart
@@ -158,42 +158,54 @@ class PixelUint8 extends Iterable<num> implements Pixel {
 
   @override
   num get g => palette == null
-      ? numChannels > 1
-          ? data[_index + 1]
-          : 0
+      ? numChannels == 2
+          ? data[_index]
+          : numChannels > 1
+              ? data[_index + 1]
+              : 0
       : palette!.getGreen(data[_index]);
 
   @override
   set g(num g) {
-    if (image.numChannels > 1) {
+    if (numChannels == 2) {
+      data[_index] = g.clamp(0, 255).toInt();
+    } else if (image.numChannels > 1) {
       data[_index + 1] = g.clamp(0, 255).toInt();
     }
   }
 
   @override
   num get b => palette == null
-      ? numChannels > 2
-          ? data[_index + 2]
-          : 0
+      ? numChannels == 2
+          ? data[_index]
+          : numChannels > 2
+              ? data[_index + 2]
+              : 0
       : palette!.getBlue(data[_index]);
 
   @override
   set b(num b) {
-    if (image.numChannels > 2) {
+    if (numChannels == 2) {
+      data[_index] = b.clamp(0, 255).toInt();
+    } else if (image.numChannels > 2) {
       data[_index + 2] = b.clamp(0, 255).toInt();
     }
   }
 
   @override
   num get a => palette == null
-      ? numChannels > 3
-          ? data[_index + 3]
-          : 255
+      ? numChannels == 2
+          ? data[_index + 1]
+          : numChannels > 3
+              ? data[_index + 3]
+              : 255
       : palette!.getAlpha(data[_index]);
 
   @override
   set a(num a) {
-    if (image.numChannels > 3) {
+    if (numChannels == 2) {
+      data[_index + 1] = a.clamp(0, 255).toInt();
+    } else if (image.numChannels > 3) {
       data[_index + 3] = a.clamp(0, 255).toInt();
     }
   }
@@ -219,9 +231,10 @@ class PixelUint8 extends Iterable<num> implements Pixel {
   set aNormalized(num v) => a = v * maxChannelValue;
 
   @override
-  num get luminance => getLuminance(this);
+  num get luminance => numChannels == 2 ? r : getLuminance(this);
   @override
-  num get luminanceNormalized => getLuminanceNormalized(this);
+  num get luminanceNormalized =>
+      numChannels == 2 ? rNormalized : getLuminanceNormalized(this);
 
   @override
   num getChannel(Channel channel) => channel == Channel.luminance

diff --git a/lib/src/util/color_util.dart b/lib/src/util/color_util.dart
@@ -44,12 +44,27 @@ Color _convertColor(Color c, Color c2, num a) {
       c2[ci] = convertFormatValue(c[ci], fromFormat, format);
     }
   } else {
-    for (var ci = 0; ci < cl; ++ci) {
-      c2[ci] = convertFormatValue(c[ci], fromFormat, format);
-    }
-    final v = cl == 1 ? c2[0] : 0;
-    for (var ci = cl; ci < numChannels; ++ci) {
-      c2[ci] = ci == 3 ? a : v;
+    if (cl == 2) {
+      final l = convertFormatValue(c[0], fromFormat, format);
+      if (numChannels == 3) {
+        c2[0] = l;
+        c2[1] = l;
+        c2[2] = l;
+      } else {
+        final a = convertFormatValue(c[1], fromFormat, format);
+        c2[0] = l;
+        c2[1] = l;
+        c2[2] = l;
+        c2[3] = a;
+      }
+    } else {
+      for (var ci = 0; ci < cl; ++ci) {
+        c2[ci] = convertFormatValue(c[ci], fromFormat, format);
+      }
+      final v = cl == 1 ? c2[0] : 0;
+      for (var ci = cl; ci < numChannels; ++ci) {
+        c2[ci] = ci == 3 ? a : v;
+      }
     }
   }
   return c2;

diff --git a/test/_data/png/png_LA.png b/test/_data/png/png_LA.png
diff --git a/test/formats/png_test.dart b/test/formats/png_test.dart
@@ -10,6 +10,13 @@ void main() {
       const buck24Hash = 817446904;
       Image? buck24Image;
 
+      test('luminanceAlpha', () async {
+        final png = (await decodePngFile('test/_data/png/png_LA.png'))!;
+        expect(png.numChannels, equals(2));
+        final rgba = png.convert(numChannels: 4);
+        await encodePngFile('$testOutputPath/png/png_LA_rgba.png', rgba);
+      });
+
       test('hungry_180', () async {
         final png = (await decodePngFile('test/_data/png/hungry_180.png'))!;
         flip(png, direction: FlipDirection.horizontal);