| /* |
| * 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 "glsl/GrGLSL.h" |
| #include "glsl/GrGLSLFragmentProcessor.h" |
| #include "glsl/GrGLSLFragmentShaderBuilder.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() { |
| this->initClassID<DitherEffect>(); |
| this->setWillReadFragmentPosition(); |
| } |
| |
| GrGLSLFragmentProcessor* onCreateGLSLInstance() const override; |
| |
| void onGetGLSLProcessorKey(const GrGLSLCaps&, GrProcessorKeyBuilder*) const override; |
| |
| // 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); |
| |
| sk_sp<GrFragmentProcessor> DitherEffect::TestCreate(GrProcessorTestData*) { |
| return DitherEffect::Make(); |
| } |
| |
| ////////////////////////////////////////////////////////////////////////////// |
| |
| 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(%s.xy ,vec2(12.9898,78.233))) * 43758.5453);\n", |
| fragBuilder->fragmentPosition()); |
| fragBuilder->codeAppendf("\t\t%s = (1.0/255.0) * vec4(r, r, r, r) + %s;\n", |
| args.fOutputColor, GrGLSLExpr4(args.fInputColor).c_str()); |
| } |
| |
| ////////////////////////////////////////////////////////////////////////////// |
| |
| void DitherEffect::onGetGLSLProcessorKey(const GrGLSLCaps& caps, |
| GrProcessorKeyBuilder* b) const { |
| GLDitherEffect::GenKey(*this, caps, b); |
| } |
| |
| GrGLSLFragmentProcessor* DitherEffect::onCreateGLSLInstance() const { |
| return new GLDitherEffect; |
| } |
| |
| sk_sp<GrFragmentProcessor> GrDitherEffect::Make() { return DitherEffect::Make(); } |