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/*
* Copyright 2014 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "gl/builders/GrGLProgramBuilder.h"
#include "GrDitherEffect.h"
#include "gl/GrGLEffect.h"
#include "gl/GrGLSL.h"
#include "GrTBackendEffectFactory.h"
#include "SkRect.h"
//////////////////////////////////////////////////////////////////////////////
class GLDitherEffect;
class DitherEffect : public GrEffect {
public:
static GrEffect* Create() {
GR_CREATE_STATIC_EFFECT(gDitherEffect, DitherEffect, ())
return SkRef(gDitherEffect);
}
virtual ~DitherEffect() {};
static const char* Name() { return "Dither"; }
typedef GLDitherEffect GLEffect;
virtual void getConstantColorComponents(GrColor* color, uint32_t* validFlags) const SK_OVERRIDE;
virtual const GrBackendEffectFactory& getFactory() const SK_OVERRIDE {
return GrTBackendEffectFactory<DitherEffect>::getInstance();
}
private:
DitherEffect() {
this->setWillReadFragmentPosition();
}
// All dither effects are equal
virtual bool onIsEqual(const GrEffect&) const SK_OVERRIDE { return true; }
GR_DECLARE_EFFECT_TEST;
typedef GrEffect INHERITED;
};
void DitherEffect::getConstantColorComponents(GrColor* color, uint32_t* validFlags) const {
*validFlags = 0;
}
//////////////////////////////////////////////////////////////////////////////
GR_DEFINE_EFFECT_TEST(DitherEffect);
GrEffect* DitherEffect::TestCreate(SkRandom*,
GrContext*,
const GrDrawTargetCaps&,
GrTexture*[]) {
return DitherEffect::Create();
}
//////////////////////////////////////////////////////////////////////////////
class GLDitherEffect : public GrGLEffect {
public:
GLDitherEffect(const GrBackendEffectFactory&, const GrDrawEffect&);
virtual void emitCode(GrGLProgramBuilder* builder,
const GrDrawEffect& drawEffect,
const GrEffectKey& key,
const char* outputColor,
const char* inputColor,
const TransformedCoordsArray&,
const TextureSamplerArray&) SK_OVERRIDE;
private:
typedef GrGLEffect INHERITED;
};
GLDitherEffect::GLDitherEffect(const GrBackendEffectFactory& factory,
const GrDrawEffect& drawEffect)
: INHERITED (factory) {
}
void GLDitherEffect::emitCode(GrGLProgramBuilder* builder,
const GrDrawEffect& drawEffect,
const GrEffectKey& key,
const char* outputColor,
const char* inputColor,
const TransformedCoordsArray&,
const TextureSamplerArray& samplers) {
GrGLFragmentShaderBuilder* fsBuilder = builder->getFragmentShaderBuilder();
// Generate a random number based on the fragment position. For this
// random number generator, we use the "GLSL rand" function
// that seems to be floating around on the internet. It works under
// the assumption that sin(<big number>) oscillates with high frequency
// and sampling it will generate "randomness". Since we're using this
// for rendering and not cryptography it should be OK.
// For each channel c, add the random offset to the pixel to either bump
// it up or let it remain constant during quantization.
fsBuilder->codeAppendf("\t\tfloat r = "
"fract(sin(dot(%s.xy ,vec2(12.9898,78.233))) * 43758.5453);\n",
fsBuilder->fragmentPosition());
fsBuilder->codeAppendf("\t\t%s = (1.0/255.0) * vec4(r, r, r, r) + %s;\n",
outputColor, GrGLSLExpr4(inputColor).c_str());
}
//////////////////////////////////////////////////////////////////////////////
GrEffect* GrDitherEffect::Create() { return DitherEffect::Create(); }
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