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flarflar
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[Impeller] Add FilterContents::GetSourceCoverage to enable filtered saveLayer clipping. (#47183)
The new method allows a caller to ask for the coverage of the input pixels required to produce an output that spans a given area. This allows the code to clip a saveLayer that has an image filter applied to it.
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lines changed

‎impeller/aiks/aiks_unittests.cc‎

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@@ -2760,6 +2760,117 @@ TEST_P(AiksTest, TranslucentSaveLayerWithColorAndImageFilterDrawsCorrectly) {
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ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
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}
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TEST_P(AiksTest, ImageFilteredSaveLayerWithUnboundedContents) {
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Canvas canvas;
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canvas.Scale(GetContentScale());
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auto test = [&canvas](const std::shared_ptr<ImageFilter>& filter) {
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auto DrawLine = [&canvas](const Point& p0, const Point& p1,
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const Paint& p) {
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auto path = PathBuilder{}
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.AddLine(p0, p1)
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.SetConvexity(Convexity::kConvex)
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.TakePath();
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Paint paint = p;
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paint.style = Paint::Style::kStroke;
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canvas.DrawPath(path, paint);
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};
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// Registration marks for the edge of the SaveLayer
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DrawLine(Point(75, 100), Point(225, 100), {.color = Color::White()});
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DrawLine(Point(75, 200), Point(225, 200), {.color = Color::White()});
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DrawLine(Point(100, 75), Point(100, 225), {.color = Color::White()});
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DrawLine(Point(200, 75), Point(200, 225), {.color = Color::White()});
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canvas.SaveLayer({.image_filter = filter},
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Rect::MakeLTRB(100, 100, 200, 200));
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{
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// DrawPaint to verify correct behavior when the contents are unbounded.
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canvas.DrawPaint({.color = Color::Yellow()});
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// Contrasting rectangle to see interior blurring
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canvas.DrawRect(Rect::MakeLTRB(125, 125, 175, 175),
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{.color = Color::Blue()});
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}
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canvas.Restore();
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};
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test(ImageFilter::MakeBlur(Sigma{10.0}, Sigma{10.0},
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FilterContents::BlurStyle::kNormal,
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Entity::TileMode::kDecal));
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canvas.Translate({200.0, 0.0});
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test(ImageFilter::MakeDilate(Radius{10.0}, Radius{10.0}));
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canvas.Translate({200.0, 0.0});
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test(ImageFilter::MakeErode(Radius{10.0}, Radius{10.0}));
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canvas.Translate({-400.0, 200.0});
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auto rotate_filter =
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ImageFilter::MakeMatrix(Matrix::MakeTranslation({150, 150}) *
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Matrix::MakeRotationZ(Degrees{10.0}) *
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Matrix::MakeTranslation({-150, -150}),
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SamplerDescriptor{});
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test(rotate_filter);
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canvas.Translate({200.0, 0.0});
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auto rgb_swap_filter = ImageFilter::MakeFromColorFilter(
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*ColorFilter::MakeMatrix({.array = {
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0, 1, 0, 0, 0, //
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0, 0, 1, 0, 0, //
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1, 0, 0, 0, 0, //
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0, 0, 0, 1, 0 //
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}}));
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test(rgb_swap_filter);
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canvas.Translate({200.0, 0.0});
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test(ImageFilter::MakeCompose(*rotate_filter, *rgb_swap_filter));
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canvas.Translate({-400.0, 200.0});
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test(ImageFilter::MakeLocalMatrix(Matrix::MakeTranslation({25.0, 25.0}),
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*rotate_filter));
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canvas.Translate({200.0, 0.0});
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test(ImageFilter::MakeLocalMatrix(Matrix::MakeTranslation({25.0, 25.0}),
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*rgb_swap_filter));
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canvas.Translate({200.0, 0.0});
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test(ImageFilter::MakeLocalMatrix(
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Matrix::MakeTranslation({25.0, 25.0}),
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*ImageFilter::MakeCompose(*rotate_filter, *rgb_swap_filter)));
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ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
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}
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TEST_P(AiksTest, ImageFilteredUnboundedSaveLayerWithUnboundedContents) {
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Canvas canvas;
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canvas.Scale(GetContentScale());
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auto blur_filter = ImageFilter::MakeBlur(Sigma{10.0}, Sigma{10.0},
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FilterContents::BlurStyle::kNormal,
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Entity::TileMode::kDecal);
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canvas.SaveLayer({.image_filter = blur_filter}, std::nullopt);
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{
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// DrawPaint to verify correct behavior when the contents are unbounded.
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canvas.DrawPaint({.color = Color::Yellow()});
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// Contrasting rectangle to see interior blurring
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canvas.DrawRect(Rect::MakeLTRB(125, 125, 175, 175),
2867+
{.color = Color::Blue()});
2868+
}
2869+
canvas.Restore();
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2871+
ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
2872+
}
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27632874
TEST_P(AiksTest, TranslucentSaveLayerImageDrawsCorrectly) {
27642875
Canvas canvas;
27652876

‎impeller/entity/contents/filters/border_mask_blur_filter_contents.cc‎

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Original file line numberDiff line numberDiff line change
@@ -169,4 +169,15 @@ std::optional<Rect> BorderMaskBlurFilterContents::GetFilterCoverage(
169169
Size(extent.x, extent.y));
170170
}
171171

172+
std::optional<Rect> BorderMaskBlurFilterContents::GetFilterSourceCoverage(
173+
const Matrix& effect_transform,
174+
const Rect& output_limit) const {
175+
auto transformed_blur_vector =
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effect_transform.TransformDirection(Vector2(Radius{sigma_x_}.radius, 0))
177+
.Abs() +
178+
effect_transform.TransformDirection(Vector2(0, Radius{sigma_y_}.radius))
179+
.Abs();
180+
return output_limit.Expand(transformed_blur_vector);
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}
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172183
} // namespace impeller

‎impeller/entity/contents/filters/border_mask_blur_filter_contents.h‎

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@@ -27,6 +27,11 @@ class BorderMaskBlurFilterContents final : public FilterContents {
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const Entity& entity,
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const Matrix& effect_transform) const override;
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30+
// |FilterContents|
31+
std::optional<Rect> GetFilterSourceCoverage(
32+
const Matrix& effect_transform,
33+
const Rect& output_limit) const override;
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3035
private:
3136
// |FilterContents|
3237
std::optional<Entity> RenderFilter(

‎impeller/entity/contents/filters/color_filter_contents.cc‎

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@@ -99,4 +99,10 @@ std::optional<Scalar> ColorFilterContents::GetAlpha() const {
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return alpha_;
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}
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102+
std::optional<Rect> ColorFilterContents::GetFilterSourceCoverage(
103+
const Matrix& effect_transform,
104+
const Rect& output_limit) const {
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return output_limit;
106+
}
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102108
} // namespace impeller

‎impeller/entity/contents/filters/color_filter_contents.h‎

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@@ -44,6 +44,11 @@ class ColorFilterContents : public FilterContents {
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4545
std::optional<Scalar> GetAlpha() const;
4646

47+
// |FilterContents|
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std::optional<Rect> GetFilterSourceCoverage(
49+
const Matrix& effect_transform,
50+
const Rect& output_limit) const override;
51+
4752
private:
4853
AbsorbOpacity absorb_opacity_ = AbsorbOpacity::kNo;
4954
std::optional<Scalar> alpha_;

‎impeller/entity/contents/filters/directional_gaussian_blur_filter_contents.cc‎

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@@ -273,6 +273,17 @@ std::optional<Entity> DirectionalGaussianBlurFilterContents::RenderFilter(
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entity.GetBlendMode(), entity.GetClipDepth());
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}
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276+
std::optional<Rect>
277+
DirectionalGaussianBlurFilterContents::GetFilterSourceCoverage(
278+
const Matrix& effect_transform,
279+
const Rect& output_limit) const {
280+
auto transform = effect_transform.Basis();
281+
auto transformed_blur_vector =
282+
transform.TransformDirection(blur_direction_ * Radius{blur_sigma_}.radius)
283+
.Abs();
284+
return output_limit.Expand(transformed_blur_vector);
285+
}
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276287
std::optional<Rect> DirectionalGaussianBlurFilterContents::GetFilterCoverage(
277288
const FilterInput::Vector& inputs,
278289
const Entity& entity,

‎impeller/entity/contents/filters/directional_gaussian_blur_filter_contents.h‎

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@@ -69,6 +69,11 @@ class DirectionalGaussianBlurFilterContents final : public FilterContents {
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/// beginning of the chain.
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void SetIsSecondPass(bool is_second_pass);
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72+
// |FilterContents|
73+
std::optional<Rect> GetFilterSourceCoverage(
74+
const Matrix& effect_transform,
75+
const Rect& output_limit) const override;
76+
7277
// |FilterContents|
7378
std::optional<Rect> GetFilterCoverage(
7479
const FilterInput::Vector& inputs,

‎impeller/entity/contents/filters/filter_contents.cc‎

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Original file line numberDiff line numberDiff line change
@@ -229,6 +229,28 @@ std::optional<Rect> FilterContents::GetFilterCoverage(
229229
return result;
230230
}
231231

232+
std::optional<Rect> FilterContents::GetSourceCoverage(
233+
const Matrix& effect_transform,
234+
const Rect& output_limit) const {
235+
auto filter_input_coverage =
236+
GetFilterSourceCoverage(effect_transform_, output_limit);
237+
238+
if (!filter_input_coverage.has_value()) {
239+
return std::nullopt;
240+
}
241+
242+
std::optional<Rect> inputs_coverage;
243+
for (auto input : inputs_) {
244+
auto input_coverage = input->GetSourceCoverage(
245+
effect_transform, filter_input_coverage.value());
246+
if (!input_coverage.has_value()) {
247+
return std::nullopt;
248+
}
249+
inputs_coverage = Union(inputs_coverage, input_coverage.value());
250+
}
251+
return inputs_coverage;
252+
}
253+
232254
std::optional<Entity> FilterContents::GetEntity(
233255
const ContentContext& renderer,
234256
const Entity& entity,

‎impeller/entity/contents/filters/filter_contents.h‎

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@@ -132,6 +132,20 @@ class FilterContents : public Contents {
132132
// |Contents|
133133
const FilterContents* AsFilter() const override;
134134

135+
/// @brief Determines the coverage of source pixels that will be needed
136+
/// to apply this filter under the given transform and produce
137+
/// results anywhere within the indicated coverage limit.
138+
///
139+
/// This is useful for subpass rendering scenarios where a filter
140+
/// will be applied to the output of the subpass and we need to
141+
/// determine how large of a render target to allocate in order
142+
/// to collect all pixels that might affect the supplied output
143+
/// coverage limit. While we might clip the rendering of the subpass,
144+
/// we want to avoid clipping out any pixels that contribute to
145+
/// the output limit via the filtering operation.
146+
std::optional<Rect> GetSourceCoverage(const Matrix& effect_transform,
147+
const Rect& output_limit) const;
148+
135149
virtual Matrix GetLocalTransform(const Matrix& parent_transform) const;
136150

137151
Matrix GetTransform(const Matrix& parent_transform) const;
@@ -169,6 +183,10 @@ class FilterContents : public Contents {
169183
const Entity& entity,
170184
const Matrix& effect_transform) const;
171185

186+
virtual std::optional<Rect> GetFilterSourceCoverage(
187+
const Matrix& effect_transform,
188+
const Rect& output_limit) const = 0;
189+
172190
/// @brief Converts zero or more filter inputs into a render instruction.
173191
virtual std::optional<Entity> RenderFilter(
174192
const FilterInput::Vector& inputs,

‎impeller/entity/contents/filters/inputs/filter_contents_filter_input.cc‎

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@@ -43,6 +43,12 @@ std::optional<Rect> FilterContentsFilterInput::GetCoverage(
4343
return filter_->GetCoverage(entity);
4444
}
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46+
std::optional<Rect> FilterContentsFilterInput::GetSourceCoverage(
47+
const Matrix& effect_transform,
48+
const Rect& output_limit) const {
49+
return filter_->GetSourceCoverage(effect_transform, output_limit);
50+
}
51+
4652
Matrix FilterContentsFilterInput::GetLocalTransform(
4753
const Entity& entity) const {
4854
return filter_->GetLocalTransform(entity.GetTransformation());

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