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 "src/gpu/effects/GrSRGBEffect.h"
9
10 #include "src/gpu/GrFragmentProcessor.h"
11 #include "src/gpu/GrProcessor.h"
12 #include "src/gpu/glsl/GrGLSLFragmentProcessor.h"
13 #include "src/gpu/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("float nonZeroAlpha = max(color.a, 0.0001);");
51 fragBuilder->codeAppendf("color = float4(color.rgb / nonZeroAlpha, color.a);");
52 }
53 fragBuilder->codeAppendf("color = float4(%s(half(color.r)), %s(half(color.g)), "
54 "%s(half(color.b)), color.a);",
55 srgbFuncName.c_str(),
56 srgbFuncName.c_str(),
57 srgbFuncName.c_str());
58 if (srgbe.alpha() == GrSRGBEffect::Alpha::kPremul) {
59 fragBuilder->codeAppendf("color = float4(color.rgb, 1) * color.a;");
60 }
61 fragBuilder->codeAppendf("%s = half4(color);", args.fOutputColor);
62 }
63
GenKey(const GrProcessor & processor,const GrShaderCaps &,GrProcessorKeyBuilder * b)64 static inline void GenKey(const GrProcessor& processor, const GrShaderCaps&,
65 GrProcessorKeyBuilder* b) {
66 const GrSRGBEffect& srgbe = processor.cast<GrSRGBEffect>();
67 uint32_t key = static_cast<uint32_t>(srgbe.mode()) |
68 (static_cast<uint32_t>(srgbe.alpha()) << 1);
69 b->add32(key);
70 }
71
72 private:
73 typedef GrGLSLFragmentProcessor INHERITED;
74 };
75
76 ///////////////////////////////////////////////////////////////////////////////
77
GrSRGBEffect(Mode mode,Alpha alpha)78 GrSRGBEffect::GrSRGBEffect(Mode mode, Alpha alpha)
79 : INHERITED(kGrSRGBEffect_ClassID, kPreservesOpaqueInput_OptimizationFlag |
80 kConstantOutputForConstantInput_OptimizationFlag)
81 , fMode(mode)
82 , fAlpha(alpha)
83 {
84 }
85
clone() const86 std::unique_ptr<GrFragmentProcessor> GrSRGBEffect::clone() const { return Make(fMode, fAlpha); }
87
onIsEqual(const GrFragmentProcessor & s) const88 bool GrSRGBEffect::onIsEqual(const GrFragmentProcessor& s) const {
89 const GrSRGBEffect& other = s.cast<GrSRGBEffect>();
90 return other.fMode == fMode;
91 }
92
srgb_to_linear(float srgb)93 static inline float srgb_to_linear(float srgb) {
94 return (srgb <= 0.04045f) ? srgb / 12.92f : powf((srgb + 0.055f) / 1.055f, 2.4f);
95 }
linear_to_srgb(float linear)96 static inline float linear_to_srgb(float linear) {
97 return (linear <= 0.0031308) ? linear * 12.92f : 1.055f * powf(linear, 1.f / 2.4f) - 0.055f;
98 }
99
constantOutputForConstantInput(const SkPMColor4f & inColor) const100 SkPMColor4f GrSRGBEffect::constantOutputForConstantInput(const SkPMColor4f& inColor) const {
101 SkColor4f color = inColor.unpremul();
102 switch (fMode) {
103 case Mode::kLinearToSRGB:
104 color = { linear_to_srgb(color.fR), linear_to_srgb(color.fG), linear_to_srgb(color.fB),
105 color.fA };
106 break;
107 case Mode::kSRGBToLinear:
108 color = { srgb_to_linear(color.fR), srgb_to_linear(color.fG), srgb_to_linear(color.fB),
109 color.fA };
110 break;
111 }
112 return color.premul();
113 }
114
115 ///////////////////////////////////////////////////////////////////////////////
116
117 GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrSRGBEffect);
118
119 #if GR_TEST_UTILS
TestCreate(GrProcessorTestData * d)120 std::unique_ptr<GrFragmentProcessor> GrSRGBEffect::TestCreate(GrProcessorTestData* d) {
121 Mode testMode = static_cast<Mode>(d->fRandom->nextRangeU(0, 1));
122 return GrSRGBEffect::Make(testMode, Alpha::kPremul);
123 }
124 #endif
125
126 ///////////////////////////////////////////////////////////////////////////////
127
onGetGLSLProcessorKey(const GrShaderCaps & caps,GrProcessorKeyBuilder * b) const128 void GrSRGBEffect::onGetGLSLProcessorKey(const GrShaderCaps& caps,
129 GrProcessorKeyBuilder* b) const {
130 GrGLSRGBEffect::GenKey(*this, caps, b);
131 }
132
onCreateGLSLInstance() const133 GrGLSLFragmentProcessor* GrSRGBEffect::onCreateGLSLInstance() const {
134 return new GrGLSRGBEffect;
135 }
136
137