[Impeller] Add filterQuality support to ImageFilter.shader (#188544)
Adds a `filterQuality` argument to `ImageFilter.shader` so the
implicitly bound image-filter input sampler can be configured instead of
always using nearest-neighbor sampling.
This threads the requested sampling quality through `dart:ui`,
DisplayList runtime-effect image filters, and Impeller’s runtime-effect
texture input setup. The default remains `FilterQuality.none` to
preserve existing behavior.
This also adds regression coverage with a fractional-texel shader to
verify that `BackdropFilter` + `ImageFilter.shader` honors
`FilterQuality`, plus equality coverage for shader image filters that
differ only by input sampling.
Fixes https://github.com/flutter/flutter/issues/188365
No changes were required in the `flutter/tests` repo.
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responsibilities, or I am not using AI tools.
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responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
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- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.
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---------
Co-authored-by: b-luk <97480502+b-luk@users.noreply.github.com>
diff --git a/engine/src/flutter/display_list/effects/dl_image_filter.cc b/engine/src/flutter/display_list/effects/dl_image_filter.cc
index 752baf6..1a66b76 100644
--- a/engine/src/flutter/display_list/effects/dl_image_filter.cc
+++ b/engine/src/flutter/display_list/effects/dl_image_filter.cc
@@ -34,9 +34,11 @@
std::shared_ptr<DlImageFilter> DlImageFilter::MakeRuntimeEffect(
sk_sp<DlRuntimeEffect> runtime_effect,
std::vector<std::shared_ptr<DlColorSource>> samplers,
- std::shared_ptr<std::vector<uint8_t>> uniform_data) {
+ std::shared_ptr<std::vector<uint8_t>> uniform_data,
+ DlImageSampling input_sampling) {
return DlRuntimeEffectImageFilter::Make(
- std::move(runtime_effect), std::move(samplers), std::move(uniform_data));
+ std::move(runtime_effect), std::move(samplers), std::move(uniform_data),
+ input_sampling);
}
std::shared_ptr<DlImageFilter> DlImageFilter::MakeColorFilter(
diff --git a/engine/src/flutter/display_list/effects/dl_image_filter.h b/engine/src/flutter/display_list/effects/dl_image_filter.h
index 911fe62..8104c54 100644
--- a/engine/src/flutter/display_list/effects/dl_image_filter.h
+++ b/engine/src/flutter/display_list/effects/dl_image_filter.h
@@ -67,7 +67,8 @@
static std::shared_ptr<DlImageFilter> MakeRuntimeEffect(
sk_sp<DlRuntimeEffect> runtime_effect,
std::vector<std::shared_ptr<DlColorSource>> samplers,
- std::shared_ptr<std::vector<uint8_t>> uniform_data);
+ std::shared_ptr<std::vector<uint8_t>> uniform_data,
+ DlImageSampling input_sampling = DlImageSampling::kNearestNeighbor);
static std::shared_ptr<DlImageFilter> MakeColorFilter(
const std::shared_ptr<const DlColorFilter>& filter);
diff --git a/engine/src/flutter/display_list/effects/dl_image_filter_unittests.cc b/engine/src/flutter/display_list/effects/dl_image_filter_unittests.cc
index aedbed3..de5c1da 100644
--- a/engine/src/flutter/display_list/effects/dl_image_filter_unittests.cc
+++ b/engine/src/flutter/display_list/effects/dl_image_filter_unittests.cc
@@ -907,6 +907,21 @@
EXPECT_NE(filter_a, filter_c);
}
+TEST(DisplayListImageFilter, RuntimeEffectEqualityWithInputSampling) {
+ DlRuntimeEffectImageFilter filter_a(nullptr, {nullptr},
+ std::make_shared<std::vector<uint8_t>>());
+ DlRuntimeEffectImageFilter filter_b(nullptr, {nullptr},
+ std::make_shared<std::vector<uint8_t>>());
+ DlRuntimeEffectImageFilter filter_c(nullptr, {nullptr},
+ std::make_shared<std::vector<uint8_t>>(),
+ DlImageSampling::kLinear);
+
+ EXPECT_EQ(filter_a.input_sampling(), DlImageSampling::kNearestNeighbor);
+ EXPECT_EQ(filter_c.input_sampling(), DlImageSampling::kLinear);
+ EXPECT_EQ(filter_a, filter_b);
+ EXPECT_NE(filter_a, filter_c);
+}
+
TEST(DisplayListImageFilter, RuntimeEffectEqualityWithSamplers) {
auto image_a =
DlColorSource::MakeImage(nullptr, DlTileMode::kClamp, DlTileMode::kDecal);
diff --git a/engine/src/flutter/display_list/effects/image_filters/dl_runtime_effect_image_filter.cc b/engine/src/flutter/display_list/effects/image_filters/dl_runtime_effect_image_filter.cc
index 9c6c285..d2c52f1 100644
--- a/engine/src/flutter/display_list/effects/image_filters/dl_runtime_effect_image_filter.cc
+++ b/engine/src/flutter/display_list/effects/image_filters/dl_runtime_effect_image_filter.cc
@@ -9,9 +9,11 @@
std::shared_ptr<DlImageFilter> DlRuntimeEffectImageFilter::Make(
sk_sp<DlRuntimeEffect> runtime_effect,
std::vector<std::shared_ptr<DlColorSource>> samplers,
- std::shared_ptr<std::vector<uint8_t>> uniform_data) {
+ std::shared_ptr<std::vector<uint8_t>> uniform_data,
+ DlImageSampling input_sampling) {
return std::make_shared<DlRuntimeEffectImageFilter>(
- std::move(runtime_effect), std::move(samplers), std::move(uniform_data));
+ std::move(runtime_effect), std::move(samplers), std::move(uniform_data),
+ input_sampling);
}
DlRect* DlRuntimeEffectImageFilter::map_local_bounds(
@@ -42,7 +44,8 @@
auto that = static_cast<const DlRuntimeEffectImageFilter*>(&other);
if (runtime_effect_ != that->runtime_effect_ ||
samplers_.size() != that->samplers().size() ||
- uniform_data_->size() != that->uniform_data()->size()) {
+ uniform_data_->size() != that->uniform_data()->size() ||
+ input_sampling_ != that->input_sampling()) {
return false;
}
for (auto i = 0u; i < samplers_.size(); i++) {
diff --git a/engine/src/flutter/display_list/effects/image_filters/dl_runtime_effect_image_filter.h b/engine/src/flutter/display_list/effects/image_filters/dl_runtime_effect_image_filter.h
index 391cfd9..ec72e58 100644
--- a/engine/src/flutter/display_list/effects/image_filters/dl_runtime_effect_image_filter.h
+++ b/engine/src/flutter/display_list/effects/image_filters/dl_runtime_effect_image_filter.h
@@ -17,20 +17,24 @@
explicit DlRuntimeEffectImageFilter(
sk_sp<DlRuntimeEffect> runtime_effect,
std::vector<std::shared_ptr<DlColorSource>> samplers,
- std::shared_ptr<std::vector<uint8_t>> uniform_data)
+ std::shared_ptr<std::vector<uint8_t>> uniform_data,
+ DlImageSampling input_sampling = DlImageSampling::kNearestNeighbor)
: runtime_effect_(std::move(runtime_effect)),
samplers_(std::move(samplers)),
- uniform_data_(std::move(uniform_data)) {}
+ uniform_data_(std::move(uniform_data)),
+ input_sampling_(input_sampling) {}
std::shared_ptr<DlImageFilter> shared() const override {
return std::make_shared<DlRuntimeEffectImageFilter>(
- this->runtime_effect_, this->samplers_, this->uniform_data_);
+ this->runtime_effect_, this->samplers_, this->uniform_data_,
+ this->input_sampling_);
}
static std::shared_ptr<DlImageFilter> Make(
sk_sp<DlRuntimeEffect> runtime_effect,
std::vector<std::shared_ptr<DlColorSource>> samplers,
- std::shared_ptr<std::vector<uint8_t>> uniform_data);
+ std::shared_ptr<std::vector<uint8_t>> uniform_data,
+ DlImageSampling input_sampling = DlImageSampling::kNearestNeighbor);
DlImageFilterType type() const override {
return DlImageFilterType::kRuntimeEffect;
@@ -66,6 +70,8 @@
return uniform_data_;
}
+ DlImageSampling input_sampling() const { return input_sampling_; }
+
protected:
bool equals_(const DlImageFilter& other) const override;
@@ -73,6 +79,7 @@
sk_sp<DlRuntimeEffect> runtime_effect_;
std::vector<std::shared_ptr<DlColorSource>> samplers_;
std::shared_ptr<std::vector<uint8_t>> uniform_data_;
+ DlImageSampling input_sampling_;
};
} // namespace flutter
diff --git a/engine/src/flutter/impeller/display_list/image_filter.cc b/engine/src/flutter/impeller/display_list/image_filter.cc
index e87964a..06981f4 100644
--- a/engine/src/flutter/impeller/display_list/image_filter.cc
+++ b/engine/src/flutter/impeller/display_list/image_filter.cc
@@ -117,13 +117,15 @@
runtime_filter->runtime_effect()->runtime_stage();
std::vector<RuntimeEffectContents::TextureInput> texture_inputs;
- size_t index = 0;
+ bool is_first = true;
for (const std::shared_ptr<flutter::DlColorSource>& sampler :
runtime_filter->samplers()) {
- if (index == 0 && sampler == nullptr) {
- // Insert placeholder for filter.
+ if (is_first) {
+ is_first = false;
+ // The first sampler is always the image filter input.
texture_inputs.push_back(
- {.sampler_descriptor = skia_conversions::ToSamplerDescriptor({}),
+ {.sampler_descriptor = skia_conversions::ToSamplerDescriptor(
+ runtime_filter->input_sampling()),
.texture = nullptr});
continue;
}
@@ -137,7 +139,6 @@
std::shared_ptr<impeller::Texture> texture =
image->image()->asImpellerImage()->GetCachedTexture(renderer);
FML_DCHECK(texture);
- index++;
texture_inputs.push_back({
.sampler_descriptor =
skia_conversions::ToSamplerDescriptor(image->sampling()),
diff --git a/engine/src/flutter/lib/ui/fixtures/shaders/general_shaders/BUILD.gn b/engine/src/flutter/lib/ui/fixtures/shaders/general_shaders/BUILD.gn
index 8b37a74..8b20c28 100644
--- a/engine/src/flutter/lib/ui/fixtures/shaders/general_shaders/BUILD.gn
+++ b/engine/src/flutter/lib/ui/fixtures/shaders/general_shaders/BUILD.gn
@@ -13,6 +13,7 @@
"circle_sdf.frag",
"double_sampler_swapped.frag",
"double_sampler.frag",
+ "filter_shader_fractional_texel.frag",
"filter_shader.frag",
"functions.frag",
"missing_size.frag",
diff --git a/engine/src/flutter/lib/ui/fixtures/shaders/general_shaders/filter_shader_fractional_texel.frag b/engine/src/flutter/lib/ui/fixtures/shaders/general_shaders/filter_shader_fractional_texel.frag
new file mode 100644
index 0000000..30a158d
--- /dev/null
+++ b/engine/src/flutter/lib/ui/fixtures/shaders/general_shaders/filter_shader_fractional_texel.frag
@@ -0,0 +1,15 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <flutter/runtime_effect.glsl>
+
+uniform vec2 u_size;
+uniform sampler2D u_texture;
+
+out vec4 frag_color;
+
+void main() {
+ vec2 uv = (FlutterFragCoord().xy + vec2(0.25, 0.0)) / u_size;
+ frag_color = texture(u_texture, uv);
+}
diff --git a/engine/src/flutter/lib/ui/painting.dart b/engine/src/flutter/lib/ui/painting.dart
index 1268cba..e1cada2 100644
--- a/engine/src/flutter/lib/ui/painting.dart
+++ b/engine/src/flutter/lib/ui/painting.dart
@@ -4429,6 +4429,9 @@
/// also be at least one sampler2D uniform, the first of which will be set by
/// the engine to contain the filter input.
///
+ /// The optional [filterQuality] argument sets the quality level used to sample
+ /// the filter input. By default, it is set to [FilterQuality.none].
+ ///
/// When Impeller uses the OpenGL(ES) backend, the y-axis direction is
/// reversed. Custom fragment shaders must invert the y-axis on
/// GLES or they will render upside-down.
@@ -4458,7 +4461,10 @@
/// }
///
/// ```
- factory ImageFilter.shader(FragmentShader shader) {
+ factory ImageFilter.shader(
+ FragmentShader shader, {
+ FilterQuality filterQuality = FilterQuality.none,
+ }) {
if (!_impellerEnabled) {
throw UnsupportedError('ImageFilter.shader only supported with Impeller rendering engine.');
}
@@ -4477,7 +4483,7 @@
}
throw StateError(buffer.toString());
}
- return _FragmentShaderImageFilter(shader);
+ return _FragmentShaderImageFilter(shader, filterQuality);
}
/// Whether [ImageFilter.shader] is supported on the current backend.
@@ -4673,9 +4679,10 @@
}
class _FragmentShaderImageFilter implements ImageFilter {
- _FragmentShaderImageFilter(this.shader);
+ _FragmentShaderImageFilter(this.shader, this.filterQuality);
final FragmentShader shader;
+ final FilterQuality filterQuality;
late final _ImageFilter nativeFilter = _ImageFilter.shader(this);
@@ -4686,7 +4693,7 @@
String get debugShortDescription => 'shader';
@override
- String toString() => 'ImageFilter.shader(Shader#${shader.hashCode})';
+ String toString() => 'ImageFilter.shader(Shader#${shader.hashCode}, $filterQuality)';
@override
bool operator ==(Object other) {
@@ -4695,6 +4702,7 @@
}
return other is _FragmentShaderImageFilter &&
other.shader == shader &&
+ other.filterQuality == filterQuality &&
_equals(nativeFilter, other.nativeFilter);
}
@@ -4702,7 +4710,7 @@
external static bool _equals(_ImageFilter a, _ImageFilter b);
@override
- int get hashCode => shader.hashCode;
+ int get hashCode => Object.hash(shader, filterQuality);
}
/// An [ImageFilter] that is backed by a native DlImageFilter.
@@ -4770,7 +4778,7 @@
_ImageFilter.shader(_FragmentShaderImageFilter filter) : creator = filter {
_constructor();
- _initShader(filter.shader);
+ _initShader(filter.shader, filter.filterQuality.index);
}
@Native<Void Function(Handle)>(symbol: 'ImageFilter::Create')
@@ -4813,8 +4821,8 @@
)
external void _initComposed(_ImageFilter outerFilter, _ImageFilter innerFilter);
- @Native<Void Function(Pointer<Void>, Pointer<Void>)>(symbol: 'ImageFilter::initShader')
- external void _initShader(FragmentShader shader);
+ @Native<Void Function(Pointer<Void>, Pointer<Void>, Int32)>(symbol: 'ImageFilter::initShader')
+ external void _initShader(FragmentShader shader, int filterQuality);
/// The original Dart object that created the native wrapper, which retains
/// the values used for the filter.
diff --git a/engine/src/flutter/lib/ui/painting/fragment_program.cc b/engine/src/flutter/lib/ui/painting/fragment_program.cc
index 74f4a33..a9b8c45 100644
--- a/engine/src/flutter/lib/ui/painting/fragment_program.cc
+++ b/engine/src/flutter/lib/ui/painting/fragment_program.cc
@@ -271,9 +271,10 @@
std::shared_ptr<DlImageFilter> FragmentProgram::MakeDlImageFilter(
std::shared_ptr<std::vector<uint8_t>> float_uniforms,
- const std::vector<std::shared_ptr<DlColorSource>>& children) {
- return DlImageFilter::MakeRuntimeEffect(runtime_effect_, children,
- std::move(float_uniforms));
+ const std::vector<std::shared_ptr<DlColorSource>>& children,
+ DlImageSampling input_sampling) {
+ return DlImageFilter::MakeRuntimeEffect(
+ runtime_effect_, children, std::move(float_uniforms), input_sampling);
}
void FragmentProgram::Create(Dart_Handle wrapper) {
diff --git a/engine/src/flutter/lib/ui/painting/fragment_program.h b/engine/src/flutter/lib/ui/painting/fragment_program.h
index 65eb460..def8c47 100644
--- a/engine/src/flutter/lib/ui/painting/fragment_program.h
+++ b/engine/src/flutter/lib/ui/painting/fragment_program.h
@@ -41,7 +41,8 @@
std::shared_ptr<DlImageFilter> MakeDlImageFilter(
std::shared_ptr<std::vector<uint8_t>> float_uniforms,
- const std::vector<std::shared_ptr<DlColorSource>>& children);
+ const std::vector<std::shared_ptr<DlColorSource>>& children,
+ DlImageSampling input_sampling = DlImageSampling::kNearestNeighbor);
private:
FragmentProgram();
diff --git a/engine/src/flutter/lib/ui/painting/fragment_shader.cc b/engine/src/flutter/lib/ui/painting/fragment_shader.cc
index 7ce2f25..bf30884 100644
--- a/engine/src/flutter/lib/ui/painting/fragment_shader.cc
+++ b/engine/src/flutter/lib/ui/painting/fragment_shader.cc
@@ -94,7 +94,8 @@
uniform_floats[float_count_ + 2 * index + 1] = image->height();
}
-std::shared_ptr<DlImageFilter> ReusableFragmentShader::as_image_filter() const {
+std::shared_ptr<DlImageFilter> ReusableFragmentShader::as_image_filter(
+ DlImageSampling input_sampling) const {
FML_CHECK(program_);
// The lifetime of this object is longer than a frame, and the uniforms can be
@@ -104,7 +105,8 @@
uniform_data->resize(uniform_data_->size());
memcpy(uniform_data->data(), uniform_data_->bytes(), uniform_data->size());
- return program_->MakeDlImageFilter(std::move(uniform_data), samplers_);
+ return program_->MakeDlImageFilter(std::move(uniform_data), samplers_,
+ input_sampling);
}
std::shared_ptr<DlColorSource> ReusableFragmentShader::shader(
diff --git a/engine/src/flutter/lib/ui/painting/fragment_shader.h b/engine/src/flutter/lib/ui/painting/fragment_shader.h
index 2246dc5..60efb48 100644
--- a/engine/src/flutter/lib/ui/painting/fragment_shader.h
+++ b/engine/src/flutter/lib/ui/painting/fragment_shader.h
@@ -47,7 +47,8 @@
// |Shader|
std::shared_ptr<DlColorSource> shader(DlImageSampling) override;
- std::shared_ptr<DlImageFilter> as_image_filter() const;
+ std::shared_ptr<DlImageFilter> as_image_filter(
+ DlImageSampling input_sampling) const;
private:
ReusableFragmentShader(fml::RefPtr<FragmentProgram> program,
diff --git a/engine/src/flutter/lib/ui/painting/image_filter.cc b/engine/src/flutter/lib/ui/painting/image_filter.cc
index 41366bb..3fb5779 100644
--- a/engine/src/flutter/lib/ui/painting/image_filter.cc
+++ b/engine/src/flutter/lib/ui/painting/image_filter.cc
@@ -131,9 +131,10 @@
inner->filter(DlTileMode::kClamp));
}
-void ImageFilter::initShader(ReusableFragmentShader* shader) {
+void ImageFilter::initShader(ReusableFragmentShader* shader,
+ int filterQualityIndex) {
FML_DCHECK(shader);
- filter_ = shader->as_image_filter();
+ filter_ = shader->as_image_filter(SamplingFromIndex(filterQualityIndex));
}
bool ImageFilter::equals(Dart_Handle a_handle, Dart_Handle b_handle) {
diff --git a/engine/src/flutter/lib/ui/painting/image_filter.h b/engine/src/flutter/lib/ui/painting/image_filter.h
index 18a71c0..4744919 100644
--- a/engine/src/flutter/lib/ui/painting/image_filter.h
+++ b/engine/src/flutter/lib/ui/painting/image_filter.h
@@ -42,7 +42,7 @@
void initMatrix(const tonic::Float64List& matrix4, int filter_quality_index);
void initColorFilter(ColorFilter* colorFilter);
void initComposeFilter(ImageFilter* outer, ImageFilter* inner);
- void initShader(ReusableFragmentShader* shader);
+ void initShader(ReusableFragmentShader* shader, int filter_quality_index);
static bool equals(Dart_Handle a_handle, Dart_Handle b_handle);
const std::shared_ptr<DlImageFilter> filter(DlTileMode mode) const;
diff --git a/engine/src/flutter/lib/web_ui/lib/painting.dart b/engine/src/flutter/lib/web_ui/lib/painting.dart
index 73f133e..94ddea1 100644
--- a/engine/src/flutter/lib/web_ui/lib/painting.dart
+++ b/engine/src/flutter/lib/web_ui/lib/painting.dart
@@ -690,8 +690,12 @@
factory ImageFilter.compose({required ImageFilter outer, required ImageFilter inner}) =>
engine.renderer.composeImageFilters(outer: outer, inner: inner);
- // ignore: avoid_unused_constructor_parameters
- factory ImageFilter.shader(FragmentShader shader) {
+ factory ImageFilter.shader(
+ // ignore: avoid_unused_constructor_parameters
+ FragmentShader shader, {
+ // ignore: avoid_unused_constructor_parameters
+ FilterQuality filterQuality = FilterQuality.none,
+ }) {
throw UnsupportedError('ImageFilter.shader only supported with Impeller rendering engine.');
}
diff --git a/engine/src/flutter/testing/dart/fragment_shader_test.dart b/engine/src/flutter/testing/dart/fragment_shader_test.dart
index e130b65..79edd1b 100644
--- a/engine/src/flutter/testing/dart/fragment_shader_test.dart
+++ b/engine/src/flutter/testing/dart/fragment_shader_test.dart
@@ -1630,6 +1630,11 @@
expect(filter, filter_2);
expect(identical(filter, filter_2), false);
+ final filterLowQuality = ImageFilter.shader(shader, filterQuality: FilterQuality.low);
+ expect(filter, isNot(filterLowQuality));
+ expect(filterLowQuality, ImageFilter.shader(shader, filterQuality: FilterQuality.low));
+ expect(identical(filter, filterLowQuality), false);
+
shader.setFloat(0, 1);
final filter_3 = ImageFilter.shader(shader);
diff --git a/engine/src/flutter/testing/dart/painting_test.dart b/engine/src/flutter/testing/dart/painting_test.dart
index dc83c2b..d8a6b2b 100644
--- a/engine/src/flutter/testing/dart/painting_test.dart
+++ b/engine/src/flutter/testing/dart/painting_test.dart
@@ -9,6 +9,7 @@
import 'package:vector_math/vector_math_64.dart';
import 'goldens.dart';
+import 'impeller_enabled.dart';
typedef CanvasCallback = void Function(Canvas canvas);
@@ -94,16 +95,9 @@
test('BackdropFilter with multiple clips', () async {
// Regression test for https://github.com/flutter/flutter/issues/144211
- Picture makePicture(CanvasCallback callback) {
- final recorder = PictureRecorder();
- final canvas = Canvas(recorder);
- callback(canvas);
- return recorder.endRecording();
- }
-
final sceneBuilder = SceneBuilder();
- final Picture redClippedPicture = makePicture((Canvas canvas) {
+ final Picture redClippedPicture = _makePicture((Canvas canvas) {
canvas.drawPaint(Paint()..color = const Color(0xFFFFFFFF));
canvas.clipRect(const Rect.fromLTRB(10, 10, 200, 200));
canvas.clipRect(const Rect.fromLTRB(11, 10, 300, 200));
@@ -114,7 +108,7 @@
final matrix = Float64List(16);
sceneBuilder.pushBackdropFilter(ImageFilter.matrix(matrix));
- final Picture whitePicture = makePicture((Canvas canvas) {
+ final Picture whitePicture = _makePicture((Canvas canvas) {
canvas.drawPaint(Paint()..color = const Color(0xFFFFFFFF));
});
sceneBuilder.addPicture(Offset.zero, whitePicture);
@@ -135,59 +129,34 @@
redClippedPicture.dispose();
});
- Image backdropBlurWithTileMode(TileMode? tileMode) {
- Picture makePicture(CanvasCallback callback) {
- final recorder = PictureRecorder();
- final canvas = Canvas(recorder);
- callback(canvas);
- return recorder.endRecording();
+ test('BackdropFilter with ImageFilter.shader honors FilterQuality', () async {
+ // Regression test for https://github.com/flutter/flutter/issues/188365.
+ if (!impellerEnabled) {
+ print('Skipped for Skia.');
+ return;
}
- const double rectSize = 10;
- const count = 50;
- const double imgSize = rectSize * count;
+ // The helper draws a black/white striped backdrop and filters it with a
+ // shader that samples the backdrop at a fractional texel coordinate. Because
+ // the stripes are grayscale, checking a single color channel is enough to
+ // tell whether the sample came from a source texel or was interpolated.
+ final Image nearest = await _backdropShaderWithFilterQuality(FilterQuality.none);
+ final Image linear = await _backdropShaderWithFilterQuality(FilterQuality.low);
- final Picture blueGreenGridPicture = makePicture((Canvas canvas) {
- const white = Color(0xFFFFFFFF);
- const purple = Color(0xFFFF00FF);
- const blue = Color(0xFF0000FF);
- const green = Color(0xFF00FF00);
- const yellow = Color(0xFFFFFF00);
- const red = Color(0xFFFF0000);
- canvas.drawColor(white, BlendMode.src);
- for (var i = 0; i < count; i++) {
- for (var j = 0; j < count; j++) {
- final rectOdd = (i + j) & 1 == 0;
- final fg = (i < count / 2)
- ? ((j < count / 2) ? green : blue)
- : ((j < count / 2) ? yellow : red);
- canvas.drawRect(
- Rect.fromLTWH(i * rectSize, j * rectSize, rectSize, rectSize),
- Paint()..color = rectOdd ? fg : white,
- );
- }
- }
- canvas.drawRect(const Rect.fromLTWH(0, 0, imgSize, 1), Paint()..color = purple);
- canvas.drawRect(const Rect.fromLTWH(0, 0, 1, imgSize), Paint()..color = purple);
- canvas.drawRect(const Rect.fromLTWH(0, imgSize - 1, imgSize, 1), Paint()..color = purple);
- canvas.drawRect(const Rect.fromLTWH(imgSize - 1, 0, 1, imgSize), Paint()..color = purple);
- });
+ // Nearest-neighbor sampling should pick either black or white exactly.
+ // Linear sampling should blend the adjacent black and white stripes.
+ final int nearestSample = await _redAt(nearest, 0, 1);
+ final int linearSample = await _redAt(linear, 0, 1);
- final sceneBuilder = SceneBuilder();
- sceneBuilder.addPicture(Offset.zero, blueGreenGridPicture);
- sceneBuilder.pushBackdropFilter(ImageFilter.blur(sigmaX: 20, sigmaY: 20, tileMode: tileMode));
+ expect(nearestSample, anyOf(0, 255));
+ expect(linearSample, allOf(greaterThan(0), lessThan(255)));
- final Scene scene = sceneBuilder.build();
- final Image image = scene.toImageSync(imgSize.round(), imgSize.round());
-
- scene.dispose();
- blueGreenGridPicture.dispose();
-
- return image;
- }
+ nearest.dispose();
+ linear.dispose();
+ });
test('BackdropFilter with Blur honors TileMode.decal', () async {
- final Image image = backdropBlurWithTileMode(TileMode.decal);
+ final Image image = _backdropBlurWithTileMode(TileMode.decal);
final ImageComparer comparer = await ImageComparer.create();
await comparer.addGoldenImage(image, 'dart_ui_backdrop_filter_blur_decal_tile_mode.png');
@@ -196,7 +165,7 @@
});
test('BackdropFilter with Blur honors TileMode.clamp', () async {
- final Image image = backdropBlurWithTileMode(TileMode.clamp);
+ final Image image = _backdropBlurWithTileMode(TileMode.clamp);
final ImageComparer comparer = await ImageComparer.create();
await comparer.addGoldenImage(image, 'dart_ui_backdrop_filter_blur_clamp_tile_mode.png');
@@ -205,7 +174,7 @@
});
test('BackdropFilter with Blur honors TileMode.mirror', () async {
- final Image image = backdropBlurWithTileMode(TileMode.mirror);
+ final Image image = _backdropBlurWithTileMode(TileMode.mirror);
final ImageComparer comparer = await ImageComparer.create();
await comparer.addGoldenImage(image, 'dart_ui_backdrop_filter_blur_mirror_tile_mode.png');
@@ -214,7 +183,7 @@
});
test('BackdropFilter with Blur honors TileMode.repeated', () async {
- final Image image = backdropBlurWithTileMode(TileMode.repeated);
+ final Image image = _backdropBlurWithTileMode(TileMode.repeated);
final ImageComparer comparer = await ImageComparer.create();
await comparer.addGoldenImage(image, 'dart_ui_backdrop_filter_blur_repeated_tile_mode.png');
@@ -223,7 +192,7 @@
});
test('BackdropFilter with Blur default TileMode acts as TileMode.mirror', () async {
- final Image image = backdropBlurWithTileMode(null);
+ final Image image = _backdropBlurWithTileMode(null);
final ImageComparer comparer = await ImageComparer.create();
// It would be nice to compare the output here to the "mirror" golden
@@ -278,3 +247,102 @@
}
});
}
+
+Picture _makePicture(CanvasCallback callback) {
+ final recorder = PictureRecorder();
+ final canvas = Canvas(recorder);
+ callback(canvas);
+ return recorder.endRecording();
+}
+
+Image _backdropBlurWithTileMode(TileMode? tileMode) {
+ const double rectSize = 10;
+ const count = 50;
+ const double imgSize = rectSize * count;
+
+ final Picture blueGreenGridPicture = _makePicture((Canvas canvas) {
+ const white = Color(0xFFFFFFFF);
+ const purple = Color(0xFFFF00FF);
+ const blue = Color(0xFF0000FF);
+ const green = Color(0xFF00FF00);
+ const yellow = Color(0xFFFFFF00);
+ const red = Color(0xFFFF0000);
+ canvas.drawColor(white, BlendMode.src);
+ for (var i = 0; i < count; i++) {
+ for (var j = 0; j < count; j++) {
+ final rectOdd = (i + j) & 1 == 0;
+ final fg = (i < count / 2)
+ ? ((j < count / 2) ? green : blue)
+ : ((j < count / 2) ? yellow : red);
+ canvas.drawRect(
+ Rect.fromLTWH(i * rectSize, j * rectSize, rectSize, rectSize),
+ Paint()..color = rectOdd ? fg : white,
+ );
+ }
+ }
+ canvas.drawRect(const Rect.fromLTWH(0, 0, imgSize, 1), Paint()..color = purple);
+ canvas.drawRect(const Rect.fromLTWH(0, 0, 1, imgSize), Paint()..color = purple);
+ canvas.drawRect(const Rect.fromLTWH(0, imgSize - 1, imgSize, 1), Paint()..color = purple);
+ canvas.drawRect(const Rect.fromLTWH(imgSize - 1, 0, 1, imgSize), Paint()..color = purple);
+ });
+
+ final sceneBuilder = SceneBuilder();
+ sceneBuilder.addPicture(Offset.zero, blueGreenGridPicture);
+ sceneBuilder.pushBackdropFilter(ImageFilter.blur(sigmaX: 20, sigmaY: 20, tileMode: tileMode));
+
+ final Scene scene = sceneBuilder.build();
+ final Image image = scene.toImageSync(imgSize.round(), imgSize.round());
+
+ scene.dispose();
+ blueGreenGridPicture.dispose();
+
+ return image;
+}
+
+Future<Image> _backdropShaderWithFilterQuality(FilterQuality filterQuality) async {
+ const width = 16;
+ const height = 4;
+ const stripeWidth = 1.0;
+
+ final FragmentProgram program = await FragmentProgram.fromAsset(
+ 'filter_shader_fractional_texel.frag.iplr',
+ );
+ final FragmentShader shader = program.fragmentShader();
+
+ final Picture stripePicture = _makePicture((Canvas canvas) {
+ for (var x = 0; x < width; x++) {
+ canvas.drawRect(
+ Rect.fromLTWH(x * stripeWidth, 0, stripeWidth, height.toDouble()),
+ Paint()..color = x.isEven ? const Color(0xFF000000) : const Color(0xFFFFFFFF),
+ );
+ }
+ });
+
+ final Picture transparentPicture = _makePicture((Canvas canvas) {
+ canvas.drawRect(
+ Rect.fromLTWH(0, 0, width.toDouble(), height.toDouble()),
+ Paint()..color = const Color(0x00000000),
+ );
+ });
+
+ final sceneBuilder = SceneBuilder();
+ sceneBuilder.addPicture(Offset.zero, stripePicture);
+ sceneBuilder.pushBackdropFilter(ImageFilter.shader(shader, filterQuality: filterQuality));
+ sceneBuilder.addPicture(Offset.zero, transparentPicture);
+ sceneBuilder.pop();
+
+ final Scene scene = sceneBuilder.build();
+ final Image image = scene.toImageSync(width, height);
+
+ scene.dispose();
+ stripePicture.dispose();
+ transparentPicture.dispose();
+ shader.dispose();
+
+ return image;
+}
+
+Future<int> _redAt(Image image, int x, int y) async {
+ final ByteData data = (await image.toByteData())!;
+ return data.getUint8((y * image.width + x) * 4);
+}
