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* Copyright 2006 The Android Open Source Project
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#ifndef SkColorFilter_DEFINED
#define SkColorFilter_DEFINED
#include "SkBlendMode.h"
#include "SkColor.h"
#include "SkFlattenable.h"
#include "SkRefCnt.h"
class GrContext;
class GrFragmentProcessor;
class SkArenaAlloc;
class SkBitmap;
class SkColorSpace;
class SkColorSpaceXformer;
class SkRasterPipeline;
* ColorFilters are optional objects in the drawing pipeline. When present in
* a paint, they are called with the "src" colors, and return new colors, which
* are then passed onto the next stage (either ImageFilter or Xfermode).
* All subclasses are required to be reentrant-safe : it must be legal to share
* the same instance between several threads.
class SK_API SkColorFilter : public SkFlattenable {
* If the filter can be represented by a source color plus Mode, this
* returns true, and sets (if not NULL) the color and mode appropriately.
* If not, this returns false and ignores the parameters.
virtual bool asColorMode(SkColor* color, SkBlendMode* bmode) const;
* If the filter can be represented by a 5x4 matrix, this
* returns true, and sets the matrix appropriately.
* If not, this returns false and ignores the parameter.
virtual bool asColorMatrix(SkScalar matrix[20]) const;
* If the filter can be represented by per-component table, return true,
* and if table is not null, copy the bitmap containing the table into it.
* The table bitmap will be in SkBitmap::kA8_Config. Each row corresponding
* to each component in ARGB order. e.g. row[0] == alpha, row[1] == red,
* etc. To transform a color, you (logically) perform the following:
* a' = *table.getAddr8(a, 0);
* r' = *table.getAddr8(r, 1);
* g' = *table.getAddr8(g, 2);
* b' = *table.getAddr8(b, 3);
* The original component value is the horizontal index for a given row,
* and the stored value at that index is the new value for that component.
virtual bool asComponentTable(SkBitmap* table) const;
void appendStages(SkRasterPipeline*, SkColorSpace*, SkArenaAlloc*, bool shaderIsOpaque) const;
enum Flags {
/** If set the filter methods will not change the alpha channel of the colors.
kAlphaUnchanged_Flag = 1 << 0,
/** Returns the flags for this filter. Override in subclasses to return custom flags.
virtual uint32_t getFlags() const { return 0; }
* If this subclass can optimally createa composition with the inner filter, return it as
* a new filter (which the caller must unref() when it is done). If no such optimization
* is known, return NULL.
* e.g. result(color) == this_filter(inner(color))
virtual sk_sp<SkColorFilter> makeComposed(sk_sp<SkColorFilter>) const { return nullptr; }
SkColor filterColor(SkColor) const;
SkColor4f filterColor4f(const SkColor4f&) const;
/** Create a colorfilter that uses the specified color and mode.
If the Mode is DST, this function will return NULL (since that
mode will have no effect on the result).
@param c The source color used with the specified mode
@param mode The blend that is applied to each color in
the colorfilter's filterSpan[16,32] methods
@return colorfilter object that applies the src color and mode,
or NULL if the mode will have no effect.
static sk_sp<SkColorFilter> MakeModeFilter(SkColor c, SkBlendMode mode);
/** Construct a colorfilter whose effect is to first apply the inner filter and then apply
* the outer filter to the result of the inner's.
* The reference counts for outer and inner are incremented.
* Due to internal limits, it is possible that this will return NULL, so the caller must
* always check.
static sk_sp<SkColorFilter> MakeComposeFilter(sk_sp<SkColorFilter> outer,
sk_sp<SkColorFilter> inner);
/** Construct a color filter that transforms a color by a 4x5 matrix. The matrix is in row-
* major order and the translation column is specified in unnormalized, 0...255, space.
static sk_sp<SkColorFilter> MakeMatrixFilterRowMajor255(const SkScalar array[20]);
/** Construct a colorfilter that applies the srgb gamma curve to the RGB channels */
static sk_sp<SkColorFilter> MakeLinearToSRGBGamma();
/** Construct a colorfilter that applies the inverse of the srgb gamma curve to the
* RGB channels
static sk_sp<SkColorFilter> MakeSRGBToLinearGamma();
* A subclass may implement this factory function to work with the GPU backend. It returns
* a GrFragmentProcessor that implemets the color filter in GPU shader code.
* The fragment processor receives a premultiplied input color and produces a premultiplied
* output color.
* A null return indicates that the color filter isn't implemented for the GPU backend.
virtual sk_sp<GrFragmentProcessor> asFragmentProcessor(GrContext*,
SkColorSpace* dstColorSpace) const;
bool affectsTransparentBlack() const {
return this->filterColor(0) != 0;
SkColorFilter() {}
sk_sp<SkColorFilter> makeColorSpace(SkColorSpaceXformer* xformer) const {
return this->onMakeColorSpace(xformer);
virtual sk_sp<SkColorFilter> onMakeColorSpace(SkColorSpaceXformer*) const {
return sk_ref_sp(const_cast<SkColorFilter*>(this));
* Returns 1 if this is a single filter (not a composition of other filters), otherwise it
* reutrns the number of leaf-node filters in a composition. This should be the same value
* as the number of GrFragmentProcessors returned by asFragmentProcessors's array parameter.
* e.g. compose(filter, compose(compose(filter, filter), filter)) --> 4
virtual int privateComposedFilterCount() const { return 1; }
virtual void onAppendStages(SkRasterPipeline*, SkColorSpace*, SkArenaAlloc*,
bool shaderIsOpaque) const = 0;
friend class SkColorSpaceXformer;
friend class SkComposeColorFilter;
typedef SkFlattenable INHERITED;