1 /*
2 * Copyright 2014 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8 #include "GrDitherEffect.h"
9 #include "GrFragmentProcessor.h"
10 #include "GrInvariantOutput.h"
11 #include "SkRect.h"
12 #include "gl/GrGLProcessor.h"
13 #include "gl/GrGLSL.h"
14 #include "gl/builders/GrGLProgramBuilder.h"
15
16 //////////////////////////////////////////////////////////////////////////////
17
18 class DitherEffect : public GrFragmentProcessor {
19 public:
Create()20 static GrFragmentProcessor* Create() {
21 GR_CREATE_STATIC_PROCESSOR(gDitherEffect, DitherEffect, ())
22 return SkRef(gDitherEffect);
23 }
24
~DitherEffect()25 virtual ~DitherEffect() {};
26
name() const27 const char* name() const override { return "Dither"; }
28
29 void getGLProcessorKey(const GrGLSLCaps&, GrProcessorKeyBuilder*) const override;
30
31 GrGLFragmentProcessor* createGLInstance() const override;
32
33 private:
DitherEffect()34 DitherEffect() {
35 this->initClassID<DitherEffect>();
36 this->setWillReadFragmentPosition();
37 }
38
39 // All dither effects are equal
onIsEqual(const GrFragmentProcessor &) const40 bool onIsEqual(const GrFragmentProcessor&) const override { return true; }
41
42 void onComputeInvariantOutput(GrInvariantOutput* inout) const override;
43
44 GR_DECLARE_FRAGMENT_PROCESSOR_TEST;
45
46 typedef GrFragmentProcessor INHERITED;
47 };
48
onComputeInvariantOutput(GrInvariantOutput * inout) const49 void DitherEffect::onComputeInvariantOutput(GrInvariantOutput* inout) const {
50 inout->setToUnknown(GrInvariantOutput::kWill_ReadInput);
51 }
52
53 //////////////////////////////////////////////////////////////////////////////
54
55 GR_DEFINE_FRAGMENT_PROCESSOR_TEST(DitherEffect);
56
TestCreate(SkRandom *,GrContext *,const GrDrawTargetCaps &,GrTexture * [])57 GrFragmentProcessor* DitherEffect::TestCreate(SkRandom*,
58 GrContext*,
59 const GrDrawTargetCaps&,
60 GrTexture*[]) {
61 return DitherEffect::Create();
62 }
63
64 //////////////////////////////////////////////////////////////////////////////
65
66 class GLDitherEffect : public GrGLFragmentProcessor {
67 public:
68 GLDitherEffect(const GrProcessor&);
69
70 virtual void emitCode(GrGLFPBuilder* builder,
71 const GrFragmentProcessor& fp,
72 const char* outputColor,
73 const char* inputColor,
74 const TransformedCoordsArray&,
75 const TextureSamplerArray&) override;
76
77 private:
78 typedef GrGLFragmentProcessor INHERITED;
79 };
80
GLDitherEffect(const GrProcessor &)81 GLDitherEffect::GLDitherEffect(const GrProcessor&) {
82 }
83
emitCode(GrGLFPBuilder * builder,const GrFragmentProcessor & fp,const char * outputColor,const char * inputColor,const TransformedCoordsArray &,const TextureSamplerArray & samplers)84 void GLDitherEffect::emitCode(GrGLFPBuilder* builder,
85 const GrFragmentProcessor& fp,
86 const char* outputColor,
87 const char* inputColor,
88 const TransformedCoordsArray&,
89 const TextureSamplerArray& samplers) {
90 GrGLFragmentBuilder* fsBuilder = builder->getFragmentShaderBuilder();
91 // Generate a random number based on the fragment position. For this
92 // random number generator, we use the "GLSL rand" function
93 // that seems to be floating around on the internet. It works under
94 // the assumption that sin(<big number>) oscillates with high frequency
95 // and sampling it will generate "randomness". Since we're using this
96 // for rendering and not cryptography it should be OK.
97
98 // For each channel c, add the random offset to the pixel to either bump
99 // it up or let it remain constant during quantization.
100 fsBuilder->codeAppendf("\t\tfloat r = "
101 "fract(sin(dot(%s.xy ,vec2(12.9898,78.233))) * 43758.5453);\n",
102 fsBuilder->fragmentPosition());
103 fsBuilder->codeAppendf("\t\t%s = (1.0/255.0) * vec4(r, r, r, r) + %s;\n",
104 outputColor, GrGLSLExpr4(inputColor).c_str());
105 }
106
107 //////////////////////////////////////////////////////////////////////////////
108
getGLProcessorKey(const GrGLSLCaps & caps,GrProcessorKeyBuilder * b) const109 void DitherEffect::getGLProcessorKey(const GrGLSLCaps& caps,
110 GrProcessorKeyBuilder* b) const {
111 GLDitherEffect::GenKey(*this, caps, b);
112 }
113
createGLInstance() const114 GrGLFragmentProcessor* DitherEffect::createGLInstance() const {
115 return SkNEW_ARGS(GLDitherEffect, (*this));
116 }
117
Create()118 GrFragmentProcessor* GrDitherEffect::Create() { return DitherEffect::Create(); }
119