skia2/include/gpu/GrPaint.h
2014-07-08 06:52:35 -07:00

255 lines
8.6 KiB
C++

/*
* Copyright 2011 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef GrPaint_DEFINED
#define GrPaint_DEFINED
#include "GrColor.h"
#include "GrEffectStage.h"
#include "SkXfermode.h"
/**
* The paint describes how color and coverage are computed at each pixel by GrContext draw
* functions and the how color is blended with the destination pixel.
*
* The paint allows installation of custom color and coverage stages. New types of stages are
* created by subclassing GrEffect.
*
* The primitive color computation starts with the color specified by setColor(). This color is the
* input to the first color stage. Each color stage feeds its output to the next color stage. The
* final color stage's output color is input to the color filter specified by
* setXfermodeColorFilter which produces the final source color, S.
*
* Fractional pixel coverage follows a similar flow. The coverage is initially the value specified
* by setCoverage(). This is input to the first coverage stage. Coverage stages are chained
* together in the same manner as color stages. The output of the last stage is modulated by any
* fractional coverage produced by anti-aliasing. This last step produces the final coverage, C.
*
* setBlendFunc() specifies blending coefficients for S (described above) and D, the initial value
* of the destination pixel, labeled Bs and Bd respectively. The final value of the destination
* pixel is then D' = (1-C)*D + C*(Bd*D + Bs*S).
*
* Note that the coverage is applied after the blend. This is why they are computed as distinct
* values.
*
* TODO: Encapsulate setXfermodeColorFilter in a GrEffect and remove from GrPaint.
*/
class GrPaint {
public:
GrPaint() { this->reset(); }
GrPaint(const GrPaint& paint) { *this = paint; }
~GrPaint() {}
/**
* Sets the blending coefficients to use to blend the final primitive color with the
* destination color. Defaults to kOne for src and kZero for dst (i.e. src mode).
*/
void setBlendFunc(GrBlendCoeff srcCoeff, GrBlendCoeff dstCoeff) {
fSrcBlendCoeff = srcCoeff;
fDstBlendCoeff = dstCoeff;
}
GrBlendCoeff getSrcBlendCoeff() const { return fSrcBlendCoeff; }
GrBlendCoeff getDstBlendCoeff() const { return fDstBlendCoeff; }
/**
* The initial color of the drawn primitive. Defaults to solid white.
*/
void setColor(GrColor color) { fColor = color; }
GrColor getColor() const { return fColor; }
/**
* Applies fractional coverage to the entire drawn primitive. Defaults to 0xff.
*/
void setCoverage(uint8_t coverage) { fCoverage = coverage; }
uint8_t getCoverage() const { return fCoverage; }
/**
* Should primitives be anti-aliased or not. Defaults to false.
*/
void setAntiAlias(bool aa) { fAntiAlias = aa; }
bool isAntiAlias() const { return fAntiAlias; }
/**
* Should dithering be applied. Defaults to false.
*/
void setDither(bool dither) { fDither = dither; }
bool isDither() const { return fDither; }
/**
* Appends an additional color effect to the color computation.
*/
const GrEffect* addColorEffect(const GrEffect* effect, int attr0 = -1, int attr1 = -1) {
SkASSERT(NULL != effect);
if (!effect->willUseInputColor()) {
fColorStages.reset();
}
SkNEW_APPEND_TO_TARRAY(&fColorStages, GrEffectStage, (effect, attr0, attr1));
return effect;
}
/**
* Appends an additional coverage effect to the coverage computation.
*/
const GrEffect* addCoverageEffect(const GrEffect* effect, int attr0 = -1, int attr1 = -1) {
SkASSERT(NULL != effect);
if (!effect->willUseInputColor()) {
fCoverageStages.reset();
}
SkNEW_APPEND_TO_TARRAY(&fCoverageStages, GrEffectStage, (effect, attr0, attr1));
return effect;
}
/**
* Helpers for adding color or coverage effects that sample a texture. The matrix is applied
* to the src space position to compute texture coordinates.
*/
void addColorTextureEffect(GrTexture* texture, const SkMatrix& matrix);
void addCoverageTextureEffect(GrTexture* texture, const SkMatrix& matrix);
void addColorTextureEffect(GrTexture* texture,
const SkMatrix& matrix,
const GrTextureParams& params);
void addCoverageTextureEffect(GrTexture* texture,
const SkMatrix& matrix,
const GrTextureParams& params);
int numColorStages() const { return fColorStages.count(); }
int numCoverageStages() const { return fCoverageStages.count(); }
int numTotalStages() const { return this->numColorStages() + this->numCoverageStages(); }
const GrEffectStage& getColorStage(int s) const { return fColorStages[s]; }
const GrEffectStage& getCoverageStage(int s) const { return fCoverageStages[s]; }
GrPaint& operator=(const GrPaint& paint) {
fSrcBlendCoeff = paint.fSrcBlendCoeff;
fDstBlendCoeff = paint.fDstBlendCoeff;
fAntiAlias = paint.fAntiAlias;
fDither = paint.fDither;
fColor = paint.fColor;
fCoverage = paint.fCoverage;
fColorStages = paint.fColorStages;
fCoverageStages = paint.fCoverageStages;
return *this;
}
/**
* Resets the paint to the defaults.
*/
void reset() {
this->resetBlend();
this->resetOptions();
this->resetColor();
this->resetCoverage();
this->resetStages();
}
/**
* Determines whether the drawing with this paint is opaque with respect to both color blending
* and fractional coverage. It does not consider whether AA has been enabled on the paint or
* not. Depending upon whether multisampling or coverage-based AA is in use, AA may make the
* result only apply to the interior of primitives.
*
*/
bool isOpaque() const;
/**
* Returns true if isOpaque would return true and the paint represents a solid constant color
* draw. If the result is true, constantColor will be updated to contain the constant color.
*/
bool isOpaqueAndConstantColor(GrColor* constantColor) const;
private:
/**
* Helper for isOpaque and isOpaqueAndConstantColor.
*/
bool getOpaqueAndKnownColor(GrColor* solidColor, uint32_t* solidColorKnownComponents) const;
/**
* Called when the source coord system from which geometry is rendered changes. It ensures that
* the local coordinates seen by effects remains unchanged. oldToNew gives the transformation
* from the previous coord system to the new coord system.
*/
void localCoordChange(const SkMatrix& oldToNew) {
for (int i = 0; i < fColorStages.count(); ++i) {
fColorStages[i].localCoordChange(oldToNew);
}
for (int i = 0; i < fCoverageStages.count(); ++i) {
fCoverageStages[i].localCoordChange(oldToNew);
}
}
bool localCoordChangeInverse(const SkMatrix& newToOld) {
SkMatrix oldToNew;
bool computed = false;
for (int i = 0; i < fColorStages.count(); ++i) {
if (!computed && !newToOld.invert(&oldToNew)) {
return false;
} else {
computed = true;
}
fColorStages[i].localCoordChange(oldToNew);
}
for (int i = 0; i < fCoverageStages.count(); ++i) {
if (!computed && !newToOld.invert(&oldToNew)) {
return false;
} else {
computed = true;
}
fCoverageStages[i].localCoordChange(oldToNew);
}
return true;
}
friend class GrContext; // To access above two functions
friend class GrStencilAndCoverTextContext; // To access above two functions
SkSTArray<4, GrEffectStage> fColorStages;
SkSTArray<2, GrEffectStage> fCoverageStages;
GrBlendCoeff fSrcBlendCoeff;
GrBlendCoeff fDstBlendCoeff;
bool fAntiAlias;
bool fDither;
GrColor fColor;
uint8_t fCoverage;
void resetBlend() {
fSrcBlendCoeff = kOne_GrBlendCoeff;
fDstBlendCoeff = kZero_GrBlendCoeff;
}
void resetOptions() {
fAntiAlias = false;
fDither = false;
}
void resetColor() {
fColor = GrColorPackRGBA(0xff, 0xff, 0xff, 0xff);
}
void resetCoverage() {
fCoverage = 0xff;
}
void resetStages() {
fColorStages.reset();
fCoverageStages.reset();
}
};
#endif