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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 "SkRect.h"
#include "glsl/GrGLSLFragmentProcessor.h"
#include "glsl/GrGLSLFragmentShaderBuilder.h"
#include "../private/GrGLSL.h"
//////////////////////////////////////////////////////////////////////////////
class DitherEffect : public GrFragmentProcessor {
public:
static sk_sp<GrFragmentProcessor> Make() {
return sk_sp<GrFragmentProcessor>(new DitherEffect);
}
virtual ~DitherEffect() {}
const char* name() const override { return "Dither"; }
private:
DitherEffect() : INHERITED(kNone_OptimizationFlags) { this->initClassID<DitherEffect>(); }
GrGLSLFragmentProcessor* onCreateGLSLInstance() const override;
void onGetGLSLProcessorKey(const GrShaderCaps&, GrProcessorKeyBuilder*) const override;
// All dither effects are equal
bool onIsEqual(const GrFragmentProcessor&) const override { return true; }
GR_DECLARE_FRAGMENT_PROCESSOR_TEST;
typedef GrFragmentProcessor INHERITED;
};
//////////////////////////////////////////////////////////////////////////////
GR_DEFINE_FRAGMENT_PROCESSOR_TEST(DitherEffect);
#if GR_TEST_UTILS
sk_sp<GrFragmentProcessor> DitherEffect::TestCreate(GrProcessorTestData*) {
return DitherEffect::Make();
}
#endif
//////////////////////////////////////////////////////////////////////////////
class GLDitherEffect : public GrGLSLFragmentProcessor {
public:
void emitCode(EmitArgs& args) override;
private:
typedef GrGLSLFragmentProcessor INHERITED;
};
void GLDitherEffect::emitCode(EmitArgs& args) {
GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
// 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.
fragBuilder->codeAppendf("\t\tfloat r = "
"fract(sin(dot(sk_FragCoord.xy, vec2(12.9898,78.233))) * "
"43758.5453);\n");
fragBuilder->codeAppendf("\t\t%s = clamp((1.0/255.0) * vec4(r, r, r, r) + %s, 0, 1);\n",
args.fOutputColor, GrGLSLExpr4(args.fInputColor).c_str());
}
//////////////////////////////////////////////////////////////////////////////
void DitherEffect::onGetGLSLProcessorKey(const GrShaderCaps& caps,
GrProcessorKeyBuilder* b) const {
GLDitherEffect::GenKey(*this, caps, b);
}
GrGLSLFragmentProcessor* DitherEffect::onCreateGLSLInstance() const {
return new GLDitherEffect;
}
sk_sp<GrFragmentProcessor> GrDitherEffect::Make() { return DitherEffect::Make(); }
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