1 /*
2 * Copyright 2016 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 "GrSRGBEffect.h"
9
10 #include "GrFragmentProcessor.h"
11 #include "GrProcessor.h"
12 #include "glsl/GrGLSLFragmentProcessor.h"
13 #include "glsl/GrGLSLFragmentShaderBuilder.h"
14
15 class GrGLSRGBEffect : public GrGLSLFragmentProcessor {
16 public:
emitCode(EmitArgs & args)17 void emitCode(EmitArgs& args) override {
18 const GrSRGBEffect& srgbe = args.fFp.cast<GrSRGBEffect>();
19 GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
20
21 SkString srgbFuncName;
22 const GrShaderVar gSrgbArgs[] = {
23 GrShaderVar("x", kHalf_GrSLType),
24 };
25 switch (srgbe.mode()) {
26 case GrSRGBEffect::Mode::kLinearToSRGB:
27 fragBuilder->emitFunction(kHalf_GrSLType,
28 "linear_to_srgb",
29 SK_ARRAY_COUNT(gSrgbArgs),
30 gSrgbArgs,
31 "return (x <= 0.0031308) ? (x * 12.92) "
32 ": (1.055 * pow(x, 0.416666667) - 0.055);",
33 &srgbFuncName);
34 break;
35 case GrSRGBEffect::Mode::kSRGBToLinear:
36 fragBuilder->emitFunction(kHalf_GrSLType,
37 "srgb_to_linear",
38 SK_ARRAY_COUNT(gSrgbArgs),
39 gSrgbArgs,
40 "return (x <= 0.04045) ? (x / 12.92) "
41 ": pow((x + 0.055) / 1.055, 2.4);",
42 &srgbFuncName);
43 break;
44 }
45
46 // Mali Bifrost uses fp16 for mediump. Making the intermediate color variable highp causes
47 // calculations to be performed with sufficient precision.
48 fragBuilder->codeAppendf("float4 color = %s;", args.fInputColor);
49 if (srgbe.alpha() == GrSRGBEffect::Alpha::kPremul) {
50 fragBuilder->codeAppendf("half nonZeroAlpha = max(color.a, 0.00001);");
51 fragBuilder->codeAppendf("color = half4(color.rgb / nonZeroAlpha, color.a);");
52 }
53 fragBuilder->codeAppendf("color = half4(%s(color.r), %s(color.g), %s(color.b), color.a);",
54 srgbFuncName.c_str(),
55 srgbFuncName.c_str(),
56 srgbFuncName.c_str());
57 if (srgbe.alpha() == GrSRGBEffect::Alpha::kPremul) {
58 fragBuilder->codeAppendf("color = half4(color.rgb, 1) * color.a;");
59 }
60 fragBuilder->codeAppendf("%s = color;", args.fOutputColor);
61 }
62
GenKey(const GrProcessor & processor,const GrShaderCaps &,GrProcessorKeyBuilder * b)63 static inline void GenKey(const GrProcessor& processor, const GrShaderCaps&,
64 GrProcessorKeyBuilder* b) {
65 const GrSRGBEffect& srgbe = processor.cast<GrSRGBEffect>();
66 uint32_t key = static_cast<uint32_t>(srgbe.mode()) |
67 (static_cast<uint32_t>(srgbe.alpha()) << 1);
68 b->add32(key);
69 }
70
71 private:
72 typedef GrGLSLFragmentProcessor INHERITED;
73 };
74
75 ///////////////////////////////////////////////////////////////////////////////
76
GrSRGBEffect(Mode mode,Alpha alpha)77 GrSRGBEffect::GrSRGBEffect(Mode mode, Alpha alpha)
78 : INHERITED(kGrSRGBEffect_ClassID, kPreservesOpaqueInput_OptimizationFlag |
79 kConstantOutputForConstantInput_OptimizationFlag)
80 , fMode(mode)
81 , fAlpha(alpha)
82 {
83 }
84
clone() const85 std::unique_ptr<GrFragmentProcessor> GrSRGBEffect::clone() const { return Make(fMode, fAlpha); }
86
onIsEqual(const GrFragmentProcessor & s) const87 bool GrSRGBEffect::onIsEqual(const GrFragmentProcessor& s) const {
88 const GrSRGBEffect& other = s.cast<GrSRGBEffect>();
89 return other.fMode == fMode;
90 }
91
srgb_to_linear(float srgb)92 static inline float srgb_to_linear(float srgb) {
93 return (srgb <= 0.04045f) ? srgb / 12.92f : powf((srgb + 0.055f) / 1.055f, 2.4f);
94 }
linear_to_srgb(float linear)95 static inline float linear_to_srgb(float linear) {
96 return (linear <= 0.0031308) ? linear * 12.92f : 1.055f * powf(linear, 1.f / 2.4f) - 0.055f;
97 }
98
constantOutputForConstantInput(const SkPMColor4f & inColor) const99 SkPMColor4f GrSRGBEffect::constantOutputForConstantInput(const SkPMColor4f& inColor) const {
100 SkColor4f color = inColor.unpremul();
101 switch (fMode) {
102 case Mode::kLinearToSRGB:
103 color = { linear_to_srgb(color.fR), linear_to_srgb(color.fG), linear_to_srgb(color.fB),
104 color.fA };
105 break;
106 case Mode::kSRGBToLinear:
107 color = { srgb_to_linear(color.fR), srgb_to_linear(color.fG), srgb_to_linear(color.fB),
108 color.fA };
109 break;
110 }
111 return color.premul();
112 }
113
114 ///////////////////////////////////////////////////////////////////////////////
115
116 GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrSRGBEffect);
117
118 #if GR_TEST_UTILS
TestCreate(GrProcessorTestData * d)119 std::unique_ptr<GrFragmentProcessor> GrSRGBEffect::TestCreate(GrProcessorTestData* d) {
120 Mode testMode = static_cast<Mode>(d->fRandom->nextRangeU(0, 1));
121 return GrSRGBEffect::Make(testMode, Alpha::kPremul);
122 }
123 #endif
124
125 ///////////////////////////////////////////////////////////////////////////////
126
onGetGLSLProcessorKey(const GrShaderCaps & caps,GrProcessorKeyBuilder * b) const127 void GrSRGBEffect::onGetGLSLProcessorKey(const GrShaderCaps& caps,
128 GrProcessorKeyBuilder* b) const {
129 GrGLSRGBEffect::GenKey(*this, caps, b);
130 }
131
onCreateGLSLInstance() const132 GrGLSLFragmentProcessor* GrSRGBEffect::onCreateGLSLInstance() const {
133 return new GrGLSRGBEffect;
134 }
135
136