improve convertColor to 1-channel; fix bmp encoder for 1bpp images

.gitignore

@@ -4,3 +4,4 @@ out/
 pubspec.lock
 .packages
 .DS_Store
+_out/

analysis_options.yaml

@@ -84,8 +84,3 @@ linter:
   - unnecessary_string_interpolations
   - use_string_buffers
   - void_checks
-
-analyzer:
-  strong-mode:
-    implicit-casts: false
-    implicit-dynamic: false

lib/src/formats/bmp_encoder.dart

@@ -9,13 +9,13 @@ import 'encoder.dart';
 
 /// Encode a BMP image.
 class BmpEncoder extends Encoder {
-  int _roundToMultiple(int x) {
+  /*int _roundToMultiple(int x) {
     final y = x & 0x3;
     if (y == 0) {
       return x;
     }
     return x + 4 - y;
-  }
+  }*/
 
   @override
   Uint8List encode(Image image, {bool singleFrame = false}) {
@@ -101,7 +101,7 @@ class BmpEncoder extends Encoder {
     final headerSize = headerInfoSize + 14;
     final paletteSize = (image.palette?.numColors ?? 0) * 4;
     final origImageOffset = headerSize + paletteSize;
-    final imageOffset = _roundToMultiple(origImageOffset);
+    final imageOffset = origImageOffset; //_roundToMultiple(origImageOffset);
     final gapSize = imageOffset - origImageOffset;
     final fileSize = imageFileSize + headerSize + paletteSize + gapSize;
 

lib/src/util/color_util.dart

@@ -35,7 +35,10 @@ Color _convertColor(Color c, Color c2, num a) {
   final format = c2.format;
   final fromFormat = c.palette?.format ?? c.format;
   final cl = c.length;
-  if (numChannels <= cl) {
+  if (numChannels == 1) {
+    final g = c.length > 2 ? c.luminance : c[0];
+    c2[0] = convertFormatValue(g, fromFormat, format);
+  } else if (numChannels <= cl) {
     for (var ci = 0; ci < numChannels; ++ci) {
       c2[ci] = convertFormatValue(c[ci], fromFormat, format);
     }

test/_test_util.dart

@@ -6,7 +6,7 @@ import 'package:image/image.dart';
 import 'package:test/test.dart';
 
 final testOutputPath = '${Directory.systemTemp.createTempSync().path}/out';
-//const testOutputPath = './out';
+//const testOutputPath = './_out';
 
 int hashImage(Image image) {
   var hash = 0;

test/image/image_test.dart

@@ -169,5 +169,13 @@ void main() {
         }
       }
     });
+    test('alpha_bmp_1bpp', () async {
+      final img = await decodePngFile('test/_data/png/alpha_bmp.png');
+      final bg = Image(width: img!.width, height: img.height)
+        ..clear(ColorRgb8(255, 255, 255));
+      compositeImage(bg, img);
+      final bpp1 = bg.convert(format: Format.uint1, numChannels: 1);
+      await encodeBmpFile('$testOutputPath/bmp/alpha_bmp_cvt.bmp', bpp1);
+    });
   });
 }

test/transform/copy_resize_test.dart

@@ -19,10 +19,10 @@ void main() {
 
     test('copyResize palette', () async {
       final img = await decodePngFile('test/_data/png/test.png');
-      final i0 = copyResize(img!, width: 64,
-          interpolation: Interpolation.cubic);
-      await encodePngFile('$testOutputPath/transform/copyResize_palette.png',
-          i0);
+      final i0 =
+          copyResize(img!, width: 64, interpolation: Interpolation.cubic);
+      await encodePngFile(
+          '$testOutputPath/transform/copyResize_palette.png', i0);
     });
   });
 }