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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 "SkColor.h"
#include "SkFlattenable.h"
#include "SkRefCnt.h"
#include "SkXfermode.h"
class GrContext;
class GrFragmentProcessor;
class SkBitmap;
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 {
public:
/**
* 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, SkXfermode::Mode* mode) 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;
/** Called with a scanline of colors, as if there was a shader installed.
The implementation writes out its filtered version into result[].
Note: shader and result may be the same buffer.
@param src array of colors, possibly generated by a shader
@param count the number of entries in the src[] and result[] arrays
@param result written by the filter
*/
virtual void filterSpan(const SkPMColor src[], int count, SkPMColor result[]) const = 0;
virtual void filterSpan4f(const SkPM4f src[], int count, SkPM4f result[]) const;
bool appendStages(SkRasterPipeline*) 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; }
/**
* Apply this colorfilter to the specified SkColor. This routine handles
* converting to SkPMColor, calling the filter, and then converting back
* to SkColor. This method is not virtual, but will call filterSpan()
* which is virtual.
*/
SkColor filterColor(SkColor) const;
/**
* Filters a single color.
*/
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 xfermode mode 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, SkXfermode::Mode mode);
static sk_sp<SkColorFilter> MakeModeFilter(SkColor c, SkBlendMode mode) {
return MakeModeFilter(c, (SkXfermode::Mode)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]);
#if SK_SUPPORT_GPU
/**
* 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*) const;
#endif
bool affectsTransparentBlack() const {
return this->filterColor(0) != 0;
}
SK_TO_STRING_PUREVIRT()
SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
SK_DEFINE_FLATTENABLE_TYPE(SkColorFilter)
protected:
SkColorFilter() {}
virtual bool onAppendStages(SkRasterPipeline*) const;
private:
/*
* 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; }
friend class SkComposeColorFilter;
typedef SkFlattenable INHERITED;
};
#endif
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