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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 "GrDitherEffect.h"
#include "GrFragmentProcessor.h"
#include "GrInvariantOutput.h"
#include "SkRect.h"
#include "gl/GrGLFragmentProcessor.h"
#include "gl/builders/GrGLProgramBuilder.h"
//////////////////////////////////////////////////////////////////////////////
class DitherEffect : public GrFragmentProcessor {
public:
static GrFragmentProcessor* Create() {
GR_CREATE_STATIC_PROCESSOR(gDitherEffect, DitherEffect, ())
return SkRef(gDitherEffect);
}
virtual ~DitherEffect() {};
const char* name() const override { return "Dither"; }
void getGLProcessorKey(const GrGLSLCaps&, GrProcessorKeyBuilder*) const override;
GrGLFragmentProcessor* createGLInstance() const override;
private:
DitherEffect() {
this->initClassID<DitherEffect>();
this->setWillReadFragmentPosition();
}
// All dither effects are equal
bool onIsEqual(const GrFragmentProcessor&) const override { return true; }
void onComputeInvariantOutput(GrInvariantOutput* inout) const override;
GR_DECLARE_FRAGMENT_PROCESSOR_TEST;
typedef GrFragmentProcessor INHERITED;
};
void DitherEffect::onComputeInvariantOutput(GrInvariantOutput* inout) const {
inout->setToUnknown(GrInvariantOutput::kWill_ReadInput);
}
//////////////////////////////////////////////////////////////////////////////
GR_DEFINE_FRAGMENT_PROCESSOR_TEST(DitherEffect);
GrFragmentProcessor* DitherEffect::TestCreate(GrProcessorTestData*) {
return DitherEffect::Create();
}
//////////////////////////////////////////////////////////////////////////////
class GLDitherEffect : public GrGLFragmentProcessor {
public:
GLDitherEffect(const GrProcessor&);
virtual void emitCode(EmitArgs& args) override;
private:
typedef GrGLFragmentProcessor INHERITED;
};
GLDitherEffect::GLDitherEffect(const GrProcessor&) {
}
void GLDitherEffect::emitCode(EmitArgs& args) {
GrGLFragmentBuilder* fsBuilder = args.fBuilder->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",
args.fOutputColor, GrGLSLExpr4(args.fInputColor).c_str());
}
//////////////////////////////////////////////////////////////////////////////
void DitherEffect::getGLProcessorKey(const GrGLSLCaps& caps,
GrProcessorKeyBuilder* b) const {
GLDitherEffect::GenKey(*this, caps, b);
}
GrGLFragmentProcessor* DitherEffect::createGLInstance() const {
return SkNEW_ARGS(GLDitherEffect, (*this));
}
GrFragmentProcessor* GrDitherEffect::Create() { return DitherEffect::Create(); }
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