@@ -177,7 +177,7 @@ class DecorationImage {
177177 /// image needs to be repainted, e.g. because it is loading incrementally or
178178 /// because it is animated.
179179DecorationImagePainter createPainter (VoidCallback onChanged) {
180- return DecorationImagePainter ._(this , onChanged);
180+ return _DecorationImagePainter ._(this , onChanged);
181181 }
182182
183183 @override
@@ -246,6 +246,28 @@ class DecorationImage {
246246 ];
247247 return '${objectRuntimeType (this , 'DecorationImage' )}(${properties .join (", " )})' ;
248248 }
249+
250+ /// Linearly interpolates between two [DecorationImage] s.
251+ ///
252+ /// The `t` argument represents position on the timeline, with 0.0 meaning
253+ /// that the interpolation has not started, returning `a` , 1.0 meaning that
254+ /// the interpolation has finished, returning `b` , and values in between
255+ /// meaning that the interpolation is at the relevant point on the timeline
256+ /// between `a` and `this` . The interpolation can be extrapolated beyond 0.0
257+ /// and 1.0, so negative values and values greater than 1.0 are valid (and can
258+ /// easily be generated by curves such as [Curves.elasticInOut] ).
259+ ///
260+ /// Values for `t` are usually obtained from an [Animation<double>] , such as
261+ /// an [AnimationController] .
262+ static DecorationImage ? lerp (DecorationImage ? a, DecorationImage ? b, double t) {
263+ if (identical (a, b) || t == 0.0 ) {
264+ return a;
265+ }
266+ if (t == 1.0 ) {
267+ return b;
268+ }
269+ return _BlendedDecorationImage (a, b, t);
270+ }
249271}
250272
251273/// The painter for a [DecorationImage] .
@@ -259,15 +281,7 @@ class DecorationImage {
259281///
260282/// This object should be disposed using the [dispose] method when it is no
261283/// longer needed.
262- class DecorationImagePainter {
263- DecorationImagePainter ._(this ._details, this ._onChanged);
264-
265- final DecorationImage _details;
266- final VoidCallback _onChanged;
267-
268- ImageStream ? _imageStream;
269- ImageInfo ? _image;
270-
284+ abstract interface class DecorationImagePainter {
271285 /// Draw the image onto the given canvas.
272286 ///
273287 /// The image is drawn at the position and size given by the `rect` argument.
@@ -282,8 +296,34 @@ class DecorationImagePainter {
282296 /// because it had not yet been loaded the first time this method was called,
283297 /// then the `onChanged` callback passed to [DecorationImage.createPainter]
284298 /// will be called.
285- void paint (Canvas canvas, Rect rect, Path ? clipPath, ImageConfiguration configuration) {
299+ ///
300+ /// The `blend` argument specifies the opacity that should be applied to the
301+ /// image due to this image being blended with another. The `blendMode`
302+ /// argument can be specified to override the [DecorationImagePainter] 's
303+ /// default [BlendMode] behavior. It is usually set to [BlendMode.srcOver] if
304+ /// this is the first or only image being blended, and [BlendMode.plus] if it
305+ /// is being blended with an image below.
306+ void paint (Canvas canvas, Rect rect, Path ? clipPath, ImageConfiguration configuration, { double blend = 1.0 , BlendMode blendMode = BlendMode .srcOver });
286307
308+ /// Releases the resources used by this painter.
309+ ///
310+ /// This should be called whenever the painter is no longer needed.
311+ ///
312+ /// After this method has been called, the object is no longer usable.
313+ void dispose ();
314+ }
315+
316+ class _DecorationImagePainter implements DecorationImagePainter {
317+ _DecorationImagePainter ._(this ._details, this ._onChanged);
318+
319+ final DecorationImage _details;
320+ final VoidCallback _onChanged;
321+
322+ ImageStream ? _imageStream;
323+ ImageInfo ? _image;
324+
325+ @override
326+ void paint (Canvas canvas, Rect rect, Path ? clipPath, ImageConfiguration configuration, { double blend = 1.0 , BlendMode blendMode = BlendMode .srcOver }) {
287327 bool flipHorizontally = false ;
288328 if (_details.matchTextDirection) {
289329 assert (() {
@@ -338,10 +378,11 @@ class DecorationImagePainter {
338378 centerSlice: _details.centerSlice,
339379 repeat: _details.repeat,
340380 flipHorizontally: flipHorizontally,
341- opacity: _details.opacity,
381+ opacity: _details.opacity * blend ,
342382 filterQuality: _details.filterQuality,
343383 invertColors: _details.invertColors,
344384 isAntiAlias: _details.isAntiAlias,
385+ blendMode: blendMode,
345386 );
346387
347388 if (clipPath != null ) {
@@ -364,12 +405,7 @@ class DecorationImagePainter {
364405 }
365406 }
366407
367- /// Releases the resources used by this painter.
368- ///
369- /// This should be called whenever the painter is no longer needed.
370- ///
371- /// After this method has been called, the object is no longer usable.
372- @mustCallSuper
408+ @override
373409 void dispose () {
374410 _imageStream? .removeListener (ImageStreamListener (
375411 _handleImage,
@@ -444,7 +480,7 @@ void debugFlushLastFrameImageSizeInfo() {
444480/// corners of the destination rectangle defined by applying `fit`. The
445481/// remaining five regions are drawn by stretching them to fit such that they
446482/// exactly cover the destination rectangle while maintaining their relative
447- /// positions.
483+ /// positions. See also [Canvas.drawImageNine].
448484///
449485/// * `repeat` : If the image does not fill `rect` , whether and how the image
450486/// should be repeated to fill `rect`. By default, the image is not repeated.
@@ -490,6 +526,7 @@ void paintImage({
490526 bool invertColors = false ,
491527 FilterQuality filterQuality = FilterQuality .low,
492528 bool isAntiAlias = false ,
529+ BlendMode blendMode = BlendMode .srcOver,
493530}) {
494531 assert (
495532 image.debugGetOpenHandleStackTraces ()? .isNotEmpty ?? true ,
@@ -530,9 +567,10 @@ void paintImage({
530567 if (colorFilter != null ) {
531568 paint.colorFilter = colorFilter;
532569 }
533- paint.color = Color .fromRGBO (0 , 0 , 0 , opacity);
570+ paint.color = Color .fromRGBO (0 , 0 , 0 , clampDouble ( opacity, 0.0 , 1.0 ) );
534571 paint.filterQuality = filterQuality;
535572 paint.invertColors = invertColors;
573+ paint.blendMode = blendMode;
536574 final double halfWidthDelta = (outputSize.width - destinationSize.width) / 2.0 ;
537575 final double halfHeightDelta = (outputSize.height - destinationSize.height) / 2.0 ;
538576 final double dx = halfWidthDelta + (flipHorizontally ? - alignment.x : alignment.x) * halfWidthDelta;
@@ -543,6 +581,12 @@ void paintImage({
543581 // Set to true if we added a saveLayer to the canvas to invert/flip the image.
544582 bool invertedCanvas = false ;
545583 // Output size and destination rect are fully calculated.
584+
585+ // Implement debug-mode and profile-mode features:
586+ // - cacheWidth/cacheHeight warning
587+ // - debugInvertOversizedImages
588+ // - debugOnPaintImage
589+ // - Flutter.ImageSizesForFrame events in timeline
546590 if (! kReleaseMode) {
547591 // We can use the devicePixelRatio of the views directly here (instead of
548592 // going through a MediaQuery) because if it changes, whatever is aware of
@@ -554,7 +598,6 @@ void paintImage({
554598 0.0 ,
555599 (double previousValue, ui.FlutterView view) => math.max (previousValue, view.devicePixelRatio),
556600 );
557-
558601 final ImageSizeInfo sizeInfo = ImageSizeInfo (
559602 // Some ImageProvider implementations may not have given this.
560603 source: debugImageLabel ?? '<Unknown Image(${image .width }×${image .height })>' ,
@@ -599,7 +642,7 @@ void paintImage({
599642 return true ;
600643 }());
601644 // Avoid emitting events that are the same as those emitted in the last frame.
602- if (! kReleaseMode && ! _lastFrameImageSizeInfo.contains (sizeInfo)) {
645+ if (! _lastFrameImageSizeInfo.contains (sizeInfo)) {
603646 final ImageSizeInfo ? existingSizeInfo = _pendingImageSizeInfo[sizeInfo.source];
604647 if (existingSizeInfo == null || existingSizeInfo.displaySizeInBytes < sizeInfo.displaySizeInBytes) {
605648 _pendingImageSizeInfo[sizeInfo.source! ] = sizeInfo;
@@ -691,3 +734,99 @@ Iterable<Rect> _generateImageTileRects(Rect outputRect, Rect fundamentalRect, Im
691734}
692735
693736Rect _scaleRect (Rect rect, double scale) => Rect .fromLTRB (rect.left * scale, rect.top * scale, rect.right * scale, rect.bottom * scale);
737+
738+ // Implements DecorationImage.lerp when the image is different.
739+ //
740+ // This class just paints both decorations on top of each other, blended together.
741+ //
742+ // The Decoration properties are faked by just forwarded to the target image.
743+ class _BlendedDecorationImage implements DecorationImage {
744+ const _BlendedDecorationImage (this .a, this .b, this .t) : assert (a != null || b != null );
745+
746+ final DecorationImage ? a;
747+ final DecorationImage ? b;
748+ final double t;
749+
750+ @override
751+ ImageProvider get image => b? .image ?? a! .image;
752+ @override
753+ ImageErrorListener ? get onError => b? .onError ?? a! .onError;
754+ @override
755+ ColorFilter ? get colorFilter => b? .colorFilter ?? a! .colorFilter;
756+ @override
757+ BoxFit ? get fit => b? .fit ?? a! .fit;
758+ @override
759+ AlignmentGeometry get alignment => b? .alignment ?? a! .alignment;
760+ @override
761+ Rect ? get centerSlice => b? .centerSlice ?? a! .centerSlice;
762+ @override
763+ ImageRepeat get repeat => b? .repeat ?? a! .repeat;
764+ @override
765+ bool get matchTextDirection => b? .matchTextDirection ?? a! .matchTextDirection;
766+ @override
767+ double get scale => b? .scale ?? a! .scale;
768+ @override
769+ double get opacity => b? .opacity ?? a! .opacity;
770+ @override
771+ FilterQuality get filterQuality => b? .filterQuality ?? a! .filterQuality;
772+ @override
773+ bool get invertColors => b? .invertColors ?? a! .invertColors;
774+ @override
775+ bool get isAntiAlias => b? .isAntiAlias ?? a! .isAntiAlias;
776+
777+ @override
778+ DecorationImagePainter createPainter (VoidCallback onChanged) {
779+ return _BlendedDecorationImagePainter ._(
780+ a? .createPainter (onChanged),
781+ b? .createPainter (onChanged),
782+ t,
783+ );
784+ }
785+
786+ @override
787+ bool operator == (Object other) {
788+ if (identical (this , other)) {
789+ return true ;
790+ }
791+ if (other.runtimeType != runtimeType) {
792+ return false ;
793+ }
794+ return other is _BlendedDecorationImage
795+ && other.a == a
796+ && other.b == b
797+ && other.t == t;
798+ }
799+
800+ @override
801+ int get hashCode => Object .hash (a, b, t);
802+
803+ @override
804+ String toString () {
805+ return '${objectRuntimeType (this , '_BlendedDecorationImage' )}($a , $b , $t )' ;
806+ }
807+ }
808+
809+ class _BlendedDecorationImagePainter implements DecorationImagePainter {
810+ _BlendedDecorationImagePainter ._(this .a, this .b, this .t);
811+
812+ final DecorationImagePainter ? a;
813+ final DecorationImagePainter ? b;
814+ final double t;
815+
816+ @override
817+ void paint (Canvas canvas, Rect rect, Path ? clipPath, ImageConfiguration configuration, { double blend = 1.0 , BlendMode blendMode = BlendMode .srcOver }) {
818+ a? .paint (canvas, rect, clipPath, configuration, blend: blend * (1.0 - t), blendMode: blendMode);
819+ b? .paint (canvas, rect, clipPath, configuration, blend: blend * t, blendMode: a != null ? BlendMode .plus : blendMode);
820+ }
821+
822+ @override
823+ void dispose () {
824+ a? .dispose ();
825+ b? .dispose ();
826+ }
827+
828+ @override
829+ String toString () {
830+ return '${objectRuntimeType (this , '_BlendedDecorationImagePainter' )}($a , $b , $t )' ;
831+ }
832+ }
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