1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
|
/*
* 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 "gl/builders/GrGLProgramBuilder.h"
#include "GrDitherEffect.h"
#include "gl/GrGLProcessor.h"
#include "gl/GrGLSL.h"
#include "GrTBackendProcessorFactory.h"
#include "SkRect.h"
//////////////////////////////////////////////////////////////////////////////
class GLDitherEffect;
class DitherEffect : public GrFragmentProcessor {
public:
static GrFragmentProcessor* Create() {
GR_CREATE_STATIC_FRAGMENT_PROCESSOR(gDitherEffect, DitherEffect, ())
return SkRef(gDitherEffect);
}
virtual ~DitherEffect() {};
static const char* Name() { return "Dither"; }
typedef GLDitherEffect GLProcessor;
virtual const GrBackendFragmentProcessorFactory& getFactory() const SK_OVERRIDE {
return GrTBackendFragmentProcessorFactory<DitherEffect>::getInstance();
}
private:
DitherEffect() {
this->setWillReadFragmentPosition();
}
// All dither effects are equal
virtual bool onIsEqual(const GrProcessor&) const SK_OVERRIDE { return true; }
virtual void onComputeInvariantOutput(InvariantOutput* inout) const SK_OVERRIDE;
GR_DECLARE_FRAGMENT_PROCESSOR_TEST;
typedef GrFragmentProcessor INHERITED;
};
void DitherEffect::onComputeInvariantOutput(InvariantOutput* inout) const {
inout->fValidFlags = 0;
inout->fIsSingleComponent = false;
}
//////////////////////////////////////////////////////////////////////////////
GR_DEFINE_FRAGMENT_PROCESSOR_TEST(DitherEffect);
GrFragmentProcessor* DitherEffect::TestCreate(SkRandom*,
GrContext*,
const GrDrawTargetCaps&,
GrTexture*[]) {
return DitherEffect::Create();
}
//////////////////////////////////////////////////////////////////////////////
class GLDitherEffect : public GrGLFragmentProcessor {
public:
GLDitherEffect(const GrBackendProcessorFactory&, const GrProcessor&);
virtual void emitCode(GrGLProgramBuilder* builder,
const GrFragmentProcessor& fp,
const GrProcessorKey& key,
const char* outputColor,
const char* inputColor,
const TransformedCoordsArray&,
const TextureSamplerArray&) SK_OVERRIDE;
private:
typedef GrGLFragmentProcessor INHERITED;
};
GLDitherEffect::GLDitherEffect(const GrBackendProcessorFactory& factory,
const GrProcessor&)
: INHERITED (factory) {
}
void GLDitherEffect::emitCode(GrGLProgramBuilder* builder,
const GrFragmentProcessor& fp,
const GrProcessorKey& key,
const char* outputColor,
const char* inputColor,
const TransformedCoordsArray&,
const TextureSamplerArray& samplers) {
GrGLFragmentShaderBuilder* 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->fragmentPosition());
fsBuilder->codeAppendf("\t\t%s = (1.0/255.0) * vec4(r, r, r, r) + %s;\n",
outputColor, GrGLSLExpr4(inputColor).c_str());
}
//////////////////////////////////////////////////////////////////////////////
GrFragmentProcessor* GrDitherEffect::Create() { return DitherEffect::Create(); }
|
