blob: 2589c3bb1e39974b190c5bfed9fc9a3e017b5f85 [file] [log] [blame]
* 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/GrGLProcessor.h"
#include "gl/GrGLSL.h"
#include "gl/builders/GrGLProgramBuilder.h"
class DitherEffect : public GrFragmentProcessor {
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;
DitherEffect() {
// All dither effects are equal
bool onIsEqual(const GrFragmentProcessor&) const override { return true; }
void onComputeInvariantOutput(GrInvariantOutput* inout) const override;
typedef GrFragmentProcessor INHERITED;
void DitherEffect::onComputeInvariantOutput(GrInvariantOutput* inout) const {
GrFragmentProcessor* DitherEffect::TestCreate(SkRandom*,
const GrCaps&,
GrTexture*[]) {
return DitherEffect::Create();
class GLDitherEffect : public GrGLFragmentProcessor {
GLDitherEffect(const GrProcessor&);
virtual void emitCode(GrGLFPBuilder* builder,
const GrFragmentProcessor& fp,
const char* outputColor,
const char* inputColor,
const TransformedCoordsArray&,
const TextureSamplerArray&) override;
typedef GrGLFragmentProcessor INHERITED;
GLDitherEffect::GLDitherEffect(const GrProcessor&) {
void GLDitherEffect::emitCode(GrGLFPBuilder* builder,
const GrFragmentProcessor& fp,
const char* outputColor,
const char* inputColor,
const TransformedCoordsArray&,
const TextureSamplerArray& samplers) {
GrGLFragmentBuilder* 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->codeAppendf("\t\t%s = (1.0/255.0) * vec4(r, r, r, r) + %s;\n",
outputColor, GrGLSLExpr4(inputColor).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(); }