Add resize function for in-place resizing

lib/image.dart

@@ -227,6 +227,7 @@ export 'src/transform/copy_resize.dart';
 export 'src/transform/copy_resize_crop_square.dart';
 export 'src/transform/copy_rotate.dart';
 export 'src/transform/flip.dart';
+export 'src/transform/resize.dart';
 export 'src/transform/trim.dart';
 export 'src/util/binary_quantizer.dart';
 export 'src/util/clip_line.dart';

lib/src/image/image_data.dart

@@ -7,8 +7,8 @@ import 'palette.dart';
 import 'pixel.dart';
 
 abstract class ImageData extends Iterable<Pixel> {
-  final int width;
-  final int height;
+  int width;
+  int height;
   final int numChannels;
 
   ImageData(this.width, this.height, this.numChannels);

lib/src/transform/resize.dart

@@ -0,0 +1,190 @@
+import 'dart:typed_data';
+
+import '../color/color.dart';
+import '../image/image.dart';
+import '../image/interpolation.dart';
+import '../util/image_exception.dart';
+import 'bake_orientation.dart';
+import 'copy_resize.dart';
+
+Image resize(Image src,
+    {int? width,
+      int? height,
+      bool? maintainAspect,
+      Color? backgroundColor,
+      Interpolation interpolation = Interpolation.nearest}) {
+  if (width == null && height == null) {
+    throw ImageException('Invalid size');
+  }
+
+  // You can't interpolate index pixels
+  if (src.hasPalette) {
+    interpolation = Interpolation.nearest;
+  }
+
+  if (src.exif.imageIfd.hasOrientation && src.exif.imageIfd.orientation != 1) {
+    src = bakeOrientation(src);
+  }
+
+  var x1 = 0;
+  var y1 = 0;
+  var x2 = 0;
+  var y2 = 0;
+
+  // this block sets [width] and [height] if null or negative.
+  if (width != null && height != null && maintainAspect == true) {
+    x1 = 0;
+    x2 = width;
+    final srcAspect = src.height / src.width;
+    final h = (width * srcAspect).toInt();
+    final dy = (height - h) ~/ 2;
+    y1 = dy;
+    y2 = y1 + h;
+    if (y1 < 0 || y2 > height) {
+      y1 = 0;
+      y2 = height;
+      final srcAspect = src.width / src.height;
+      final w = (height * srcAspect).toInt();
+      final dx = (width - w) ~/ 2;
+      x1 = dx;
+      x2 = x1 + w;
+    }
+  } else {
+    maintainAspect = false;
+  }
+
+  if (height == null || height <= 0) {
+    height = (width! * (src.height / src.width)).round();
+  }
+  if (width == null || width <= 0) {
+    width = (height * (src.width / src.height)).round();
+  }
+
+  final w = maintainAspect! ? x2 - x1 : width;
+  final h = maintainAspect ? y2 - y1 : height;
+
+  if (!maintainAspect) {
+    x1 = 0;
+    x2 = width;
+    y1 = 0;
+    y2 = height;
+  }
+
+  if (width == src.width && height == src.height) {
+    return src;
+  }
+
+  if ((width * height) > (src.width * src.height)) {
+    return copyResize(src, width: width, height: height,
+        maintainAspect: maintainAspect, backgroundColor: backgroundColor,
+        interpolation: interpolation);
+  }
+
+  final scaleX = Int32List(w);
+  final dx = src.width / w;
+  for (var x = 0; x < w; ++x) {
+    scaleX[x] = (x * dx).toInt();
+  }
+
+  final origWidth = src.width;
+  final origHeight = src.height;
+
+  final numFrames = src.numFrames;
+  for (var i = 0; i < numFrames; ++i) {
+    final frame = src.frames[i];
+    final dst = frame;
+
+    final dy = frame.height / h;
+    final dx = frame.width / w;
+
+    if (maintainAspect && backgroundColor != null) {
+      dst.clear(backgroundColor);
+    }
+
+    if (interpolation == Interpolation.average) {
+      for (var y = 0; y < h; ++y) {
+        final ay1 = (y * dy).toInt();
+        var ay2 = ((y + 1) * dy).toInt();
+        if (ay2 == ay1) {
+          ay2++;
+        }
+
+        for (var x = 0; x < w; ++x) {
+          final ax1 = (x * dx).toInt();
+          var ax2 = ((x + 1) * dx).toInt();
+          if (ax2 == ax1) {
+            ax2++;
+          }
+
+          num r = 0;
+          num g = 0;
+          num b = 0;
+          num a = 0;
+          var np = 0;
+          for (var sy = ay1; sy < ay2; ++sy) {
+            for (var sx = ax1; sx < ax2; ++sx, ++np) {
+              final s = frame.getPixel(sx, sy);
+              r += s.r;
+              g += s.g;
+              b += s.b;
+              a += s.a;
+            }
+          }
+          final c = dst.getColor(r / np, g / np, b / np, a / np);
+
+          dst.data!.width = width;
+          dst.data!.height = height;
+          dst.setPixel(x1 + x, y1 + y, c);
+          dst.data!.width = origWidth;
+          dst.data!.height = origHeight;
+        }
+      }
+    } else if (interpolation == Interpolation.nearest) {
+      if (frame.hasPalette) {
+        for (var y = 0; y < h; ++y) {
+          final y2 = (y * dy).toInt();
+          for (var x = 0; x < w; ++x) {
+            final p = frame.getPixelIndex(scaleX[x], y2);
+            dst.data!.width = width;
+            dst.data!.height = height;
+            dst.setPixelIndex(x1 + x, y1 + y, p);
+            dst.data!.width = origWidth;
+            dst.data!.height = origHeight;
+          }
+        }
+      } else {
+        for (var y = 0; y < h; ++y) {
+          final y2 = (y * dy).toInt();
+          for (var x = 0; x < w; ++x) {
+            final p = frame.getPixel(scaleX[x], y2);
+            dst.data!.width = width;
+            dst.data!.height = height;
+            dst.setPixel(x1 + x, y1 + y, p);
+            dst.data!.width = origWidth;
+            dst.data!.height = origHeight;
+          }
+        }
+      }
+    } else {
+      // Copy the pixels from this image to the new image.
+      for (var y = 0; y < h; ++y) {
+        final sy2 = y * dy;
+        for (var x = 0; x < w; ++x) {
+          final sx2 = x * dx;
+          final p = frame.getPixelInterpolate(x1 + sx2, y1 + sy2,
+              interpolation: interpolation);
+          dst.data!.width = width;
+          dst.data!.height = height;
+          dst.setPixel(x, y, p);
+          dst.data!.width = origWidth;
+          dst.data!.height = origHeight;
+        }
+      }
+    }
+
+    dst.data!.width = width;
+    dst.data!.height = height;
+  }
+
+  return src;
+}

test/transform/resize_test.dart

@@ -0,0 +1,177 @@
+import 'dart:io';
+import 'package:image/image.dart';
+import 'package:test/test.dart';
+
+import '../_test_util.dart';
+
+void main() {
+  group('Transform', () {
+    test('resize nearest', () {
+      final img =
+          decodePng(File('test/_data/png/buck_24.png').readAsBytesSync())!;
+      final i0 = resize(img, width: 64);
+      expect(i0.width, equals(64));
+      expect(i0.height, equals(40));
+      File('$testOutputPath/transform/resize.png')
+        ..createSync(recursive: true)
+        ..writeAsBytesSync(encodePng(i0));
+    });
+
+    test('resize average', () {
+      final img =
+          decodePng(File('test/_data/png/buck_24.png').readAsBytesSync())!;
+      final i0 =
+          resize(img, width: 64, interpolation: Interpolation.average);
+      expect(i0.width, equals(64));
+      expect(i0.height, equals(40));
+      File('$testOutputPath/transform/resize_average.png')
+        ..createSync(recursive: true)
+        ..writeAsBytesSync(encodePng(i0));
+    });
+
+    test('resize linear', () {
+      final img =
+          decodePng(File('test/_data/png/buck_24.png').readAsBytesSync())!;
+      final i0 =
+          resize(img, width: 64, interpolation: Interpolation.linear);
+      expect(i0.width, equals(64));
+      expect(i0.height, equals(40));
+      File('$testOutputPath/transform/resize_linear.png')
+        ..createSync(recursive: true)
+        ..writeAsBytesSync(encodePng(i0));
+    });
+
+    test('resize cubic', () {
+      final img =
+          decodePng(File('test/_data/png/buck_24.png').readAsBytesSync())!;
+      final i0 = resize(img, width: 64, interpolation: Interpolation.cubic);
+      expect(i0.width, equals(64));
+      expect(i0.height, equals(40));
+      File('$testOutputPath/transform/resize_cubic.png')
+        ..createSync(recursive: true)
+        ..writeAsBytesSync(encodePng(i0));
+    });
+
+    test('resize maintainAspect', () {
+      final img =
+          decodePng(File('test/_data/png/buck_24.png').readAsBytesSync())!;
+      final i0 = resize(img,
+          width: 640,
+          height: 640,
+          maintainAspect: true,
+          backgroundColor: ColorRgb8(0, 0, 255));
+      expect(i0.width, equals(640));
+      expect(i0.height, equals(640));
+      File('$testOutputPath/transform/resize_maintainAspect.png')
+        ..createSync(recursive: true)
+        ..writeAsBytesSync(encodePng(i0));
+    });
+
+    test('resize maintainAspect palette', () {
+      final img =
+          decodePng(File('test/_data/png/buck_8.png').readAsBytesSync())!;
+      final i0 = resize(img,
+          width: 640,
+          height: 640,
+          maintainAspect: true,
+          backgroundColor: ColorRgb8(0, 0, 255));
+      expect(i0.width, equals(640));
+      expect(i0.height, equals(640));
+      File('$testOutputPath/transform/resize_maintainAspect_palette.png')
+        ..createSync(recursive: true)
+        ..writeAsBytesSync(encodePng(i0));
+    });
+
+    test('resize maintainAspect 2', () {
+      final i0 = Image(width: 100, height: 50)..clear(ColorRgb8(255, 0, 0));
+      final i1 = resize(i0,
+          width: 200,
+          height: 200,
+          maintainAspect: true,
+          backgroundColor: ColorRgb8(0, 0, 255));
+      expect(i1.width, equals(200));
+      expect(i1.height, equals(200));
+      File('$testOutputPath/transform/resize_maintainAspect_2.png')
+        ..createSync(recursive: true)
+        ..writeAsBytesSync(encodePng(i1));
+    });
+
+    test('resize maintainAspect 3', () {
+      final i0 = Image(width: 50, height: 100)..clear(ColorRgb8(0, 255, 0));
+      final i1 = resize(i0,
+          width: 200,
+          height: 200,
+          maintainAspect: true,
+          backgroundColor: ColorRgb8(0, 0, 255));
+      expect(i1.width, equals(200));
+      expect(i1.height, equals(200));
+      File('$testOutputPath/transform/resize_maintainAspect_3.png')
+        ..createSync(recursive: true)
+        ..writeAsBytesSync(encodePng(i1));
+    });
+
+    test('resize maintainAspect 4', () {
+      final i0 = Image(width: 100, height: 50)..clear(ColorRgb8(255, 0, 0));
+      final i1 = resize(i0,
+          width: 50,
+          height: 100,
+          maintainAspect: true,
+          backgroundColor: ColorRgb8(0, 0, 255));
+      expect(i1.width, equals(50));
+      expect(i1.height, equals(100));
+      File('$testOutputPath/transform/resize_maintainAspect_4.png')
+        ..createSync(recursive: true)
+        ..writeAsBytesSync(encodePng(i1));
+    });
+
+    test('resize maintainAspect 5', () {
+      final i0 = Image(width: 50, height: 100)..clear(ColorRgb8(0, 255, 0));
+      final i1 = resize(i0,
+          width: 100,
+          height: 50,
+          maintainAspect: true,
+          backgroundColor: ColorRgb8(0, 0, 255));
+      expect(i1.width, equals(100));
+      expect(i1.height, equals(50));
+      File('$testOutputPath/transform/resize_maintainAspect_5.png')
+        ..createSync(recursive: true)
+        ..writeAsBytesSync(encodePng(i1));
+    });
+
+    test('resize maintainAspect 5', () {
+      final i0 = Image(width: 50, height: 100)..clear(ColorRgb8(0, 255, 0));
+      final i1 = resize(i0,
+          width: 100,
+          height: 500,
+          maintainAspect: true,
+          backgroundColor: ColorRgb8(0, 0, 255));
+      expect(i1.width, equals(100));
+      expect(i1.height, equals(500));
+      File('$testOutputPath/transform/resize_maintainAspect_5.png')
+        ..createSync(recursive: true)
+        ..writeAsBytesSync(encodePng(i1));
+    });
+
+    test('resize maintainAspect 6', () {
+      final i0 = Image(width: 100, height: 50)..clear(ColorRgb8(0, 255, 0));
+      final i1 = resize(i0,
+          width: 500,
+          height: 100,
+          maintainAspect: true,
+          backgroundColor: ColorRgb8(0, 0, 255));
+      expect(i1.width, equals(500));
+      expect(i1.height, equals(100));
+      File('$testOutputPath/transform/resize_maintainAspect_6.png')
+        ..createSync(recursive: true)
+        ..writeAsBytesSync(encodePng(i1));
+    });
+
+    test('resize palette', () async {
+      final img = await decodePngFile('test/_data/png/test.png');
+      final i0 =
+          resize(img!, width: 64, interpolation: Interpolation.cubic);
+      await encodePngFile(
+          '$testOutputPath/transform/resize_palette.png', i0);
+    });
+  });
+}