| Flutter Impeller |

Public Member Functions | Static Public Member Functions | List of all members
impeller::GaussianBlurFilterContents Class Referencefinal

`#include <gaussian_blur_filter_contents.h>`

Inheritance diagram for impeller::GaussianBlurFilterContents:

## Public Member Functions
| GaussianBlurFilterContents (Scalar sigma_x, Scalar sigma_y, Entity::TileMode tile_mode)
Scalar | GetSigmaX () const
Scalar | GetSigmaY () const
std::optional< Rect > | GetFilterSourceCoverage (const Matrix &effect_transform, const Rect &output_limit) const override
| Internal utility method for |GetSourceCoverage| that computes the inverse effect of this transform on the specified output coverage, ignoring the inputs which will be accommodated by the caller. More...
std::optional< Rect > | GetFilterCoverage (const FilterInput::Vector &inputs, const Entity &entity, const Matrix &effect_transform) const override
| Internal utility method for |GetLocalCoverage| that computes the output coverage of this filter across the specified inputs, ignoring the coverage hint. More...
Public Member Functions inherited from impeller::FilterContents
| FilterContents ()
| ~FilterContents () override
void | SetInputs (FilterInput::Vector inputs)
| The input texture sources for this filter. Each input's emitted texture is expected to have premultiplied alpha colors. More...
void | SetEffectTransform (const Matrix &effect_transform)
| Sets the transform which gets appended to the effect of this filter. Note that this is in addition to the entity's transform. More...
std::optional< Entity > | GetEntity (const ContentContext &renderer, const Entity &entity, const std::optional< Rect > &coverage_hint) const
| Create an Entity that renders this filter's output. More...
bool | Render (const ContentContext &renderer, const Entity &entity, RenderPass &pass) const override
std::optional< Rect > | GetCoverage (const Entity &entity) const override
| Get the area of the render pass that will be affected when this contents is rendered. More...
void | PopulateGlyphAtlas (const std::shared_ptr< LazyGlyphAtlas > &lazy_glyph_atlas, Scalar scale) override
| Add any text data to the specified lazy atlas. The scale parameter must be used again later when drawing the text. More...
std::optional< Snapshot > | RenderToSnapshot (const ContentContext &renderer, const Entity &entity, std::optional< Rect > coverage_limit=std::nullopt, const std::optional< SamplerDescriptor > &sampler_descriptor=std::nullopt, bool msaa_enabled=true, const std::string &label="Filter Snapshot") const override
| Render this contents to a snapshot, respecting the entity's transform, path, clip depth, and blend mode. The result texture size is always the size of `GetCoverage(entity)`. More...
const FilterContents * | AsFilter () const override
| Cast to a filter. Returns `nullptr` if this Contents is not a filter. More...
std::optional< Rect > | GetSourceCoverage (const Matrix &effect_transform, const Rect &output_limit) const
| Determines the coverage of source pixels that will be needed to produce results for the specified |output_limit| under the specified |effect_transform|. This is essentially a reverse of the |GetCoverage| method computing a source coverage from an intended |output_limit| coverage. More...
virtual Matrix | GetLocalTransform (const Matrix &parent_transform) const
Matrix | GetTransform (const Matrix &parent_transform) const
virtual bool | IsTranslationOnly () const
| Returns true if this filter graph doesn't perform any basis transforms to the filtered content. For example: Rotating, scaling, and skewing are all basis transforms, but translating is not. More...
bool | IsLeaf () const
| Returns `true` if this filter does not have any `FilterInput` children. More...
void | SetLeafInputs (const FilterInput::Vector &inputs)
| Replaces the set of all leaf `FilterContents` with a new set of `FilterInput`s. More...
virtual void | SetRenderingMode (Entity::RenderingMode rendering_mode)
| Marks this filter chain as applying in a subpass scenario. More...
Public Member Functions inherited from impeller::Contents
| Contents ()
virtual | ~Contents ()
void | SetCoverageHint (std::optional< Rect > coverage_hint)
| Hint that specifies the coverage area of this Contents that will actually be used during rendering. This is for optimization purposes only and can not be relied on as a clip. May optionally affect the result of `GetCoverage()`. More...
const std::optional< Rect > & | GetCoverageHint () const
virtual bool | IsOpaque () const
| Whether this Contents only emits opaque source colors from the fragment stage. This value does not account for any entity properties (e.g. the blend mode), clips/visibility culling, or inherited opacity. More...
virtual ClipCoverage | GetClipCoverage (const Entity &entity, const std::optional< Rect > &current_clip_coverage) const
| Given the current pass space bounding rectangle of the clip buffer, return the expected clip coverage after this draw call. This should only be implemented for contents that may write to the clip buffer. More...
virtual bool | ShouldRender (const Entity &entity, const std::optional< Rect > clip_coverage) const
std::optional< Size > | GetColorSourceSize () const
| Return the color source's intrinsic size, if available. More...
void | SetColorSourceSize (Size size)
virtual bool | CanInheritOpacity (const Entity &entity) const
| Whether or not this contents can accept the opacity peephole optimization. More...
virtual void | SetInheritedOpacity (Scalar opacity)
| Inherit the provided opacity. More...
virtual std::optional< Color > | AsBackgroundColor (const Entity &entity, ISize target_size) const
| Returns a color if this Contents will flood the given `target_size` with a color. This output color is the "Source" color that will be used for the Entity's blend operation. More...
virtual bool | ApplyColorFilter (const ColorFilterProc &color_filter_proc)
| If possible, applies a color filter to this contents inputs on the CPU. More...

## Static Public Member Functions
static Scalar | CalculateBlurRadius (Scalar sigma)
static Quad | CalculateUVs (const std::shared_ptr< FilterInput > &filter_input, const Entity &entity, const Rect &source_rect, const ISize &texture_size)
static Scalar | CalculateScale (Scalar sigma)
static Scalar | ScaleSigma (Scalar sigma)
Static Public Member Functions inherited from impeller::FilterContents
static std::shared_ptr< FilterContents > | MakeDirectionalGaussianBlur (FilterInput::Ref input, Sigma sigma, Vector2 direction, BlurStyle blur_style=BlurStyle::kNormal, Entity::TileMode tile_mode=Entity::TileMode::kDecal, bool is_second_pass=false, Sigma secondary_sigma={})
static std::shared_ptr< FilterContents > | MakeGaussianBlur (const FilterInput::Ref &input, Sigma sigma_x, Sigma sigma_y, BlurStyle blur_style=BlurStyle::kNormal, Entity::TileMode tile_mode=Entity::TileMode::kDecal)
static std::shared_ptr< FilterContents > | MakeBorderMaskBlur (FilterInput::Ref input, Sigma sigma_x, Sigma sigma_y, BlurStyle blur_style=BlurStyle::kNormal)
static std::shared_ptr< FilterContents > | MakeDirectionalMorphology (FilterInput::Ref input, Radius radius, Vector2 direction, MorphType morph_type)
static std::shared_ptr< FilterContents > | MakeMorphology (FilterInput::Ref input, Radius radius_x, Radius radius_y, MorphType morph_type)
static std::shared_ptr< FilterContents > | MakeMatrixFilter (FilterInput::Ref input, const Matrix &matrix, const SamplerDescriptor &desc)
static std::shared_ptr< FilterContents > | MakeLocalMatrixFilter (FilterInput::Ref input, const Matrix &matrix)
static std::shared_ptr< FilterContents > | MakeYUVToRGBFilter (std::shared_ptr< Texture > y_texture, std::shared_ptr< Texture > uv_texture, YUVColorSpace yuv_color_space)
Static Public Member Functions inherited from impeller::Contents
static std::shared_ptr< Contents > | MakeAnonymous (RenderProc render_proc, CoverageProc coverage_proc)

## Additional Inherited Members
Public Types inherited from impeller::FilterContents
enum | BlurStyle { BlurStyle::kNormal, BlurStyle::kSolid, BlurStyle::kOuter, BlurStyle::kInner }
enum | MorphType { MorphType::kDilate, MorphType::kErode }
Public Types inherited from impeller::Contents
using | ColorFilterProc = std::function< Color(Color)>
using | RenderProc = std::function< bool(const ContentContext &renderer, const Entity &entity, RenderPass &pass)>
using | CoverageProc = std::function< std::optional< Rect >(const Entity &entity)>

## Detailed Description

Performs a bidirectional Gaussian blur.

This is accomplished by rendering multiple passes in multiple directions. Note: This will replace `DirectionalGaussianBlurFilterContents`.

Definition at line 28 of file gaussian_blur_filter_contents.h.

## Constructor & Destructor Documentation

## ◆ GaussianBlurFilterContents()

impeller::GaussianBlurFilterContents::GaussianBlurFilterContents | ( | Scalar | sigma_x,
|  | Scalar | sigma_y,
|  | Entity::TileMode | tile_mode
| ) |  |
| explicit

Definition at line 198 of file gaussian_blur_filter_contents.cc.

202 : sigma_x_(sigma_x), sigma_y_(sigma_y), tile_mode_(tile_mode) {}

## Member Function Documentation

## ◆ CalculateBlurRadius()

Scalar impeller::GaussianBlurFilterContents::CalculateBlurRadius | ( | Scalar | sigma | ) |
| static

Given a sigma (standard deviation) calculate the blur radius (1/2 the kernel size).

Definition at line 405 of file gaussian_blur_filter_contents.cc.

405 {
406 return static_cast<Radius>(Sigma(sigma)).radius;
407 }

Referenced by GetFilterCoverage(), GetFilterSourceCoverage(), and impeller::testing::TEST().

## ◆ CalculateScale()

Scalar impeller::GaussianBlurFilterContents::CalculateScale | ( | Scalar | sigma | ) |
| static

Calculate the scale factor for the downsample pass given a sigma value.

Visible for testing.

Definition at line 207 of file gaussian_blur_filter_contents.cc.

207 {
208 if (sigma <= 4) {
209 return 1.0;
210 }
211 return 4.0 / sigma;
212 };

Referenced by impeller::testing::TEST().

## ◆ CalculateUVs()

Quad impeller::GaussianBlurFilterContents::CalculateUVs | ( | const std::shared_ptr< FilterInput > & | filter_input,
|  | const Entity & | entity,
|  | const Rect & | source_rect,
|  | const ISize & | texture_size
| ) |  |
| static

Calculate the UV coordinates for rendering the filter_input.

Parameters

  filter_input | The FilterInput that should be rendered.
  entity | The associated entity for the filter_input.
  source_rect | The rect in source coordinates to convert to uvs.
  texture_size | The rect to convert in source coordinates.

Definition at line 409 of file gaussian_blur_filter_contents.cc.

413 {
414 Matrix input_transform = filter_input->GetLocalTransform(entity);
415 Quad coverage_quad = source_rect.GetTransformedPoints(input_transform);
416
417 Matrix uv_transform = Matrix::MakeScale(
418 {1.0f / texture_size.width, 1.0f / texture_size.height, 1.0f});
419 return uv_transform.Transform(coverage_quad);
420 }

References impeller::TRect< T >::GetTransformedPoints(), impeller::TSize< T >::height, impeller::Matrix::MakeScale(), impeller::Matrix::Transform(), and impeller::TSize< T >::width.

Referenced by impeller::testing::TEST_P().

## ◆ GetFilterCoverage()

std::optional< Rect > impeller::GaussianBlurFilterContents::GetFilterCoverage | ( | const FilterInput::Vector & | inputs,
|  | const Entity & | entity,
|  | const Matrix & | effect_transform
| ) |  | const
| override virtual

Internal utility method for |GetLocalCoverage| that computes the output coverage of this filter across the specified inputs, ignoring the coverage hint.

Reimplemented from impeller::FilterContents.

Definition at line 225 of file gaussian_blur_filter_contents.cc.

228 {
229 if (inputs.empty()) {
230 return {};
231 }
232
233 std::optional<Rect> input_coverage = inputs[0]->GetCoverage(entity);
234 if (!input_coverage.has_value()) {
235 return {};
236 }
237
238 Vector2 scaled_sigma = {ScaleSigma(sigma_x_), ScaleSigma(sigma_y_)};
239 Vector2 blur_radius = {CalculateBlurRadius(scaled_sigma.x),
240 CalculateBlurRadius(scaled_sigma.y)};
241 Vector3 blur_radii =
242 (inputs[0]->GetTransform(entity).Basis() * effect_transform.Basis() *
243 Vector3{blur_radius.x, blur_radius.y, 0.0})
244 .Abs();
245 return input_coverage.value().Expand(Point(blur_radii.x, blur_radii.y));
246 }

References impeller::Matrix::Basis(), CalculateBlurRadius(), ScaleSigma(), impeller::Vector3::x, impeller::TPoint< T >::x, impeller::Vector3::y, and impeller::TPoint< T >::y.

Referenced by impeller::testing::TEST(), and impeller::testing::TEST_P().

## ◆ GetFilterSourceCoverage()

std::optional< Rect > impeller::GaussianBlurFilterContents::GetFilterSourceCoverage | ( | const Matrix & | effect_transform,
|  | const Rect & | output_limit
| ) |  | const
| override virtual

Internal utility method for |GetSourceCoverage| that computes the inverse effect of this transform on the specified output coverage, ignoring the inputs which will be accommodated by the caller.

Implements impeller::FilterContents.

Definition at line 214 of file gaussian_blur_filter_contents.cc.

216 {
217 Vector2 scaled_sigma = {ScaleSigma(sigma_x_), ScaleSigma(sigma_y_)};
218 Vector2 blur_radius = {CalculateBlurRadius(scaled_sigma.x),
219 CalculateBlurRadius(scaled_sigma.y)};
220 Vector3 blur_radii =
221 effect_transform.Basis() * Vector3{blur_radius.x, blur_radius.y, 0.0};
222 return output_limit.Expand(Point(blur_radii.x, blur_radii.y));
223 }

References impeller::Matrix::Basis(), CalculateBlurRadius(), impeller::TRect< T >::Expand(), ScaleSigma(), impeller::Vector3::x, impeller::TPoint< T >::x, impeller::Vector3::y, and impeller::TPoint< T >::y.

## ◆ GetSigmaX()

Scalar impeller::GaussianBlurFilterContents::GetSigmaX | ( |  | ) | const
| inline

Definition at line 34 of file gaussian_blur_filter_contents.h.

34 { return sigma_x_; }

Referenced by impeller::testing::TEST().

## ◆ GetSigmaY()

Scalar impeller::GaussianBlurFilterContents::GetSigmaY | ( |  | ) | const
| inline

Definition at line 35 of file gaussian_blur_filter_contents.h.

35 { return sigma_y_; }

Referenced by impeller::testing::TEST().

## ◆ ScaleSigma()

Scalar impeller::GaussianBlurFilterContents::ScaleSigma | ( | Scalar | sigma | ) |
| static

Scales down the sigma value to match Skia's behavior.

effective_blur_radius = CalculateBlurRadius(ScaleSigma(sigma_));

This function was calculated by observing Skia's behavior. Its blur at 500 seemed to be 0.15. Since we clamp at 500 I solved the quadratic equation that puts the minima there and a f(0)=1.

Definition at line 425 of file gaussian_blur_filter_contents.cc.

425 {
426 // Limit the kernel size to 1000x1000 pixels, like Skia does.
427 Scalar clamped = std::min(sigma, 500.0f);
428 constexpr Scalar a = 3.4e-06;
429 constexpr Scalar b = -3.4e-3;
430 constexpr Scalar c = 1.f;
431 Scalar scalar = c + b * clamped + a * clamped * clamped;
432 return clamped * scalar;
433 }

Referenced by GetFilterCoverage(), GetFilterSourceCoverage(), and impeller::testing::TEST().

The documentation for this class was generated from the following files:

- impeller/entity/contents/filters/gaussian_blur_filter_contents.h
- impeller/entity/contents/filters/gaussian_blur_filter_contents.cc

impeller::Scalar
float Scalar
Definition: scalar.h:18
impeller::Vector2
Point Vector2
Definition: point.h:312
impeller::GaussianBlurFilterContents::CalculateBlurRadius
static Scalar CalculateBlurRadius(Scalar sigma)
Definition: gaussian_blur_filter_contents.cc:405
impeller::Point
TPoint< Scalar > Point
Definition: point.h:308
impeller::Quad
std::array< Point, 4 > Quad
Definition: point.h:313
impeller::Matrix::Transform
constexpr Quad Transform(const Quad &quad) const
Definition: matrix.h:449
impeller::Matrix::MakeScale
static constexpr Matrix MakeScale(const Vector3 &s)
Definition: matrix.h:104
impeller::GaussianBlurFilterContents::ScaleSigma
static Scalar ScaleSigma(Scalar sigma)
Definition: gaussian_blur_filter_contents.cc:425