implement targetWidth and targetHeight (#38028)

* implement targetWidth and targetHeight

* blank lines and typo

* addressed comments

* add warning to tests

lib/web_ui/lib/src/engine/canvaskit/image.dart

@@ -11,29 +11,29 @@ import '../dom.dart';
 import '../html_image_codec.dart';
 import '../safe_browser_api.dart';
 import '../util.dart';
+import 'canvas.dart';
 import 'canvaskit_api.dart';
 import 'image_wasm_codecs.dart';
 import 'image_web_codecs.dart';
+import 'painting.dart';
+import 'picture.dart';
+import 'picture_recorder.dart';
 import 'skia_object_cache.dart';
 
 /// Instantiates a [ui.Codec] backed by an `SkAnimatedImage` from Skia.
-// TODO(yjbanov): Implement targetWidth and targetHeight support.
-//                https://github.com/flutter/flutter/issues/34075
 FutureOr<ui.Codec> skiaInstantiateImageCodec(Uint8List list,
     [int? targetWidth, int? targetHeight]) {
-  if (browserSupportsImageDecoder) {
+  // If we have either a target width or target height, use canvaskit to decode.
+  if (browserSupportsImageDecoder && (targetWidth == null && targetHeight == null)) {
     return CkBrowserImageDecoder.create(
       data: list,
       debugSource: 'encoded image bytes',
-      targetWidth: targetWidth,
-      targetHeight: targetHeight,
     );
   } else {
-    return CkAnimatedImage.decodeFromBytes(list, 'encoded image bytes');
+    return CkAnimatedImage.decodeFromBytes(list, 'encoded image bytes', targetWidth: targetWidth, targetHeight: targetHeight);
   }
 }
 
-// TODO(yjbanov): add support for targetWidth/targetHeight (https://github.com/flutter/flutter/issues/34075)
 void skiaDecodeImageFromPixels(
   Uint8List pixels,
   int width,
@@ -45,6 +45,13 @@ void skiaDecodeImageFromPixels(
   int? targetHeight,
   bool allowUpscaling = true,
 }) {
+  if (targetWidth != null) {
+    assert(allowUpscaling || targetWidth <= width);
+  }
+  if (targetHeight != null) {
+    assert(allowUpscaling || targetHeight <= height);
+  }
+
   // Run in a timer to avoid janking the current frame by moving the decoding
   // work outside the frame event.
   Timer.run(() {
@@ -65,10 +72,88 @@ void skiaDecodeImageFromPixels(
       return;
     }
 
+    if (targetWidth != null || targetHeight != null) {
+      if (!validUpscale(allowUpscaling, targetWidth, targetHeight, width, height)) {
+        domWindow.console.warn('Cannot apply targetWidth/targetHeight when allowUpscaling is false.');
+      } else {
+        return callback(scaleImage(skImage, targetWidth, targetHeight));
+      }
+    }
     return callback(CkImage(skImage));
   });
 }
 
+// An invalid upscale happens when allowUpscaling is false AND either the given
+// targetWidth is larger than the originalWidth OR the targetHeight is larger than originalHeight.
+bool validUpscale(bool allowUpscaling, int? targetWidth, int? targetHeight, int originalWidth, int originalHeight) {
+  if (allowUpscaling) {
+    return true;
+  }
+  final bool targetWidthFits;
+  final bool targetHeightFits;
+  if (targetWidth != null) {
+    targetWidthFits = targetWidth <= originalWidth;
+  } else {
+    targetWidthFits = true;
+  }
+
+  if (targetHeight != null) {
+    targetHeightFits = targetHeight <= originalHeight;
+  } else {
+    targetHeightFits = true;
+  }
+  return targetWidthFits && targetHeightFits;
+}
+
+/// Creates a scaled [CkImage] from an [SkImage] by drawing the [SkImage] to a canvas.
+///
+/// This function will only be called if either a targetWidth or targetHeight is not null
+///
+/// If only one of targetWidth or  targetHeight are specified, the other
+/// dimension will be scaled according to the aspect ratio of the supplied
+/// dimension.
+///
+/// If either targetWidth or targetHeight is less than or equal to zero, it
+/// will be treated as if it is null.
+CkImage scaleImage(SkImage image, int? targetWidth, int? targetHeight) {
+    assert(targetWidth != null || targetHeight != null);
+    if (targetWidth != null && targetWidth <= 0) {
+      targetWidth = null;
+    }
+    if (targetHeight != null && targetHeight <= 0) {
+      targetHeight = null;
+    }
+    if (targetWidth == null && targetHeight != null) {
+      targetWidth = (targetHeight * (image.width() / image.height())).round();
+      targetHeight = targetHeight;
+    } else if (targetHeight == null && targetWidth != null) {
+      targetWidth = targetWidth;
+      targetHeight = targetWidth ~/ (image.width() / image.height());
+    }
+
+    assert(targetWidth != null);
+    assert(targetHeight != null);
+
+    final CkPictureRecorder recorder = CkPictureRecorder();
+    final CkCanvas canvas = recorder.beginRecording(ui.Rect.largest);
+
+    canvas.drawImageRect(
+      CkImage(image),
+      ui.Rect.fromLTWH(0, 0, image.width(), image.height()),
+      ui.Rect.fromLTWH(0, 0, targetWidth!.toDouble(), targetHeight!.toDouble()),
+      CkPaint()
+    );
+
+    final CkPicture picture = recorder.endRecording();
+    final ui.Image finalImage = picture.toImageSync(
+      targetWidth,
+      targetHeight
+    );
+
+    final CkImage ckImage = finalImage as CkImage;
+    return ckImage;
+}
+
 /// Thrown when the web engine fails to decode an image, either due to a
 /// network issue, corrupted image contents, or missing codec.
 class ImageCodecException implements Exception {

lib/web_ui/lib/src/engine/canvaskit/image_wasm_codecs.dart

@@ -14,6 +14,7 @@ import 'dart:typed_data';
 
 import 'package:ui/ui.dart' as ui;
 
+import '../util.dart';
 import 'canvaskit_api.dart';
 import 'image.dart';
 import 'skia_object_cache.dart';
@@ -24,7 +25,7 @@ import 'skia_object_cache.dart';
 class CkAnimatedImage extends ManagedSkiaObject<SkAnimatedImage>
     implements ui.Codec {
   /// Decodes an image from a list of encoded bytes.
-  CkAnimatedImage.decodeFromBytes(this._bytes, this.src);
+  CkAnimatedImage.decodeFromBytes(this._bytes, this.src, {this.targetWidth, this.targetHeight});
 
   final String src;
   final Uint8List _bytes;
@@ -34,9 +35,12 @@ class CkAnimatedImage extends ManagedSkiaObject<SkAnimatedImage>
   /// Current frame index.
   int _currentFrameIndex = 0;
 
+  final int? targetWidth;
+  final int? targetHeight;
+
   @override
   SkAnimatedImage createDefault() {
-    final SkAnimatedImage? animatedImage =
+    SkAnimatedImage? animatedImage =
         canvasKit.MakeAnimatedImageFromEncoded(_bytes);
     if (animatedImage == null) {
       throw ImageCodecException(
@@ -45,6 +49,20 @@ class CkAnimatedImage extends ManagedSkiaObject<SkAnimatedImage>
       );
     }
 
+    if (targetWidth != null || targetHeight != null) {
+      if (animatedImage.getFrameCount() > 1) {
+        printWarning('targetWidth and targetHeight for multi-frame images not supported');
+      } else {
+        animatedImage = _resizeAnimatedImage(animatedImage, targetWidth, targetHeight);
+        if (animatedImage == null) {
+          throw ImageCodecException(
+            'Failed to decode re-sized image data.\n'
+            'Image source: $src',
+          );
+        }
+      }
+    }
+
     _frameCount = animatedImage.getFrameCount().toInt();
     _repetitionCount = animatedImage.getRepetitionCount().toInt();
 
@@ -61,6 +79,19 @@ class CkAnimatedImage extends ManagedSkiaObject<SkAnimatedImage>
     return animatedImage;
   }
 
+  SkAnimatedImage? _resizeAnimatedImage(SkAnimatedImage animatedImage, int? targetWidth, int? targetHeight) {
+    final SkImage image = animatedImage.makeImageAtCurrentFrame();
+    final CkImage ckImage = scaleImage(image, targetWidth, targetHeight);
+    final Uint8List? resizedBytes = ckImage.skImage.encodeToBytes();
+
+    if (resizedBytes == null) {
+      throw ImageCodecException('Failed to re-size image');
+    }
+
+    final SkAnimatedImage? resizedAnimatedImage = canvasKit.MakeAnimatedImageFromEncoded(resizedBytes);
+    return resizedAnimatedImage;
+  }
+
   @override
   SkAnimatedImage resurrect() => createDefault();
 

lib/web_ui/lib/src/engine/canvaskit/image_web_codecs.dart

@@ -44,17 +44,13 @@ void debugRestoreWebDecoderExpireDuration() {
 class CkBrowserImageDecoder implements ui.Codec {
   CkBrowserImageDecoder._({
     required this.contentType,
-    required this.targetWidth,
-    required this.targetHeight,
     required this.data,
     required this.debugSource,
   });
 
   static Future<CkBrowserImageDecoder> create({
     required Uint8List data,
     required String debugSource,
-    int? targetWidth,
-    int? targetHeight,
   }) async {
     // ImageDecoder does not detect image type automatically. It requires us to
     // tell it what the image type is.
@@ -76,8 +72,6 @@ class CkBrowserImageDecoder implements ui.Codec {
 
     final CkBrowserImageDecoder decoder = CkBrowserImageDecoder._(
       contentType: contentType,
-      targetWidth: targetWidth,
-      targetHeight: targetHeight,
       data: data,
       debugSource: debugSource,
     );
@@ -88,8 +82,6 @@ class CkBrowserImageDecoder implements ui.Codec {
   }
 
   final String contentType;
-  final int? targetWidth;
-  final int? targetHeight;
   final Uint8List data;
   final String debugSource;
 
@@ -160,9 +152,6 @@ class CkBrowserImageDecoder implements ui.Codec {
 
         // Flutter always uses premultiplied alpha when decoding.
         premultiplyAlpha: 'premultiply',
-        desiredWidth: targetWidth,
-        desiredHeight: targetHeight,
-
         // "default" gives the browser the liberty to convert to display-appropriate
         // color space, typically SRGB, which is what we want.
         colorSpaceConversion: 'default',

lib/web_ui/lib/src/engine/safe_browser_api.dart

@@ -280,8 +280,8 @@ class ImageDecoderOptions {
     required String type,
     required Uint8List data,
     required String premultiplyAlpha,
-    required int? desiredWidth,
-    required int? desiredHeight,
+    int? desiredWidth,
+    int? desiredHeight,
     required String colorSpaceConversion,
     required bool preferAnimation,
   });