1/*
2 * Copyright 2017 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/core/SkBlendModePriv.h"
9#include "src/core/SkRasterPipeline.h"
10
11bool SkBlendMode_ShouldPreScaleCoverage(SkBlendMode mode, bool rgb_coverage) {
12 // The most important things we do here are:
13 // 1) never pre-scale with rgb coverage if the blend mode involves a source-alpha term;
14 // 2) always pre-scale Plus.
15 //
16 // When we pre-scale with rgb coverage, we scale each of source r,g,b, with a distinct value,
17 // and source alpha with one of those three values. This process destructively updates the
18 // source-alpha term, so we can't evaluate blend modes that need its original value.
19 //
20 // Plus always requires pre-scaling as a specific quirk of its implementation in
21 // SkRasterPipeline. This lets us put the clamp inside the blend mode itself rather
22 // than as a separate stage that'd come after the lerp.
23 //
24 // This function is a finer-grained breakdown of SkBlendMode_SupportsCoverageAsAlpha().
25 switch (mode) {
26 case SkBlendMode::kDst: // d --> no sa term, ok!
27 case SkBlendMode::kDstOver: // d + s*inv(da) --> no sa term, ok!
28 case SkBlendMode::kPlus: // clamp(s+d) --> no sa term, ok!
29 return true;
30
31 case SkBlendMode::kDstOut: // d * inv(sa)
32 case SkBlendMode::kSrcATop: // s*da + d*inv(sa)
33 case SkBlendMode::kSrcOver: // s + d*inv(sa)
34 case SkBlendMode::kXor: // s*inv(da) + d*inv(sa)
35 return !rgb_coverage;
36
37 default: break;
38 }
39 return false;
40}
41
42// Users of this function may want to switch to the rgb-coverage aware version above.
43bool SkBlendMode_SupportsCoverageAsAlpha(SkBlendMode mode) {
44 return SkBlendMode_ShouldPreScaleCoverage(mode, false);
45}
46
47struct CoeffRec {
48 SkBlendModeCoeff fSrc;
49 SkBlendModeCoeff fDst;
50};
51
52const CoeffRec gCoeffs[] = {
53 // For Porter-Duff blend functions, color = src * src coeff + dst * dst coeff
54 // src coeff dst coeff blend func
55 // ---------------------- ----------------------- ----------
56 { SkBlendModeCoeff::kZero, SkBlendModeCoeff::kZero }, // clear
57 { SkBlendModeCoeff::kOne, SkBlendModeCoeff::kZero }, // src
58 { SkBlendModeCoeff::kZero, SkBlendModeCoeff::kOne }, // dst
59 { SkBlendModeCoeff::kOne, SkBlendModeCoeff::kISA }, // src-over
60 { SkBlendModeCoeff::kIDA, SkBlendModeCoeff::kOne }, // dst-over
61 { SkBlendModeCoeff::kDA, SkBlendModeCoeff::kZero }, // src-in
62 { SkBlendModeCoeff::kZero, SkBlendModeCoeff::kSA }, // dst-in
63 { SkBlendModeCoeff::kIDA, SkBlendModeCoeff::kZero }, // src-out
64 { SkBlendModeCoeff::kZero, SkBlendModeCoeff::kISA }, // dst-out
65 { SkBlendModeCoeff::kDA, SkBlendModeCoeff::kISA }, // src-atop
66 { SkBlendModeCoeff::kIDA, SkBlendModeCoeff::kSA }, // dst-atop
67 { SkBlendModeCoeff::kIDA, SkBlendModeCoeff::kISA }, // xor
68
69 { SkBlendModeCoeff::kOne, SkBlendModeCoeff::kOne }, // plus
70 { SkBlendModeCoeff::kZero, SkBlendModeCoeff::kSC }, // modulate
71 { SkBlendModeCoeff::kOne, SkBlendModeCoeff::kISC }, // screen
72};
73
74bool SkBlendMode_AsCoeff(SkBlendMode mode, SkBlendModeCoeff* src, SkBlendModeCoeff* dst) {
75 if (mode > SkBlendMode::kScreen) {
76 return false;
77 }
78 if (src) {
79 *src = gCoeffs[static_cast<int>(mode)].fSrc;
80 }
81 if (dst) {
82 *dst = gCoeffs[static_cast<int>(mode)].fDst;
83 }
84 return true;
85}
86
87void SkBlendMode_AppendStages(SkBlendMode mode, SkRasterPipeline* p) {
88 auto stage = SkRasterPipeline::srcover;
89 switch (mode) {
90 case SkBlendMode::kClear: stage = SkRasterPipeline::clear; break;
91 case SkBlendMode::kSrc: return; // This stage is a no-op.
92 case SkBlendMode::kDst: stage = SkRasterPipeline::move_dst_src; break;
93 case SkBlendMode::kSrcOver: stage = SkRasterPipeline::srcover; break;
94 case SkBlendMode::kDstOver: stage = SkRasterPipeline::dstover; break;
95 case SkBlendMode::kSrcIn: stage = SkRasterPipeline::srcin; break;
96 case SkBlendMode::kDstIn: stage = SkRasterPipeline::dstin; break;
97 case SkBlendMode::kSrcOut: stage = SkRasterPipeline::srcout; break;
98 case SkBlendMode::kDstOut: stage = SkRasterPipeline::dstout; break;
99 case SkBlendMode::kSrcATop: stage = SkRasterPipeline::srcatop; break;
100 case SkBlendMode::kDstATop: stage = SkRasterPipeline::dstatop; break;
101 case SkBlendMode::kXor: stage = SkRasterPipeline::xor_; break;
102 case SkBlendMode::kPlus: stage = SkRasterPipeline::plus_; break;
103 case SkBlendMode::kModulate: stage = SkRasterPipeline::modulate; break;
104
105 case SkBlendMode::kScreen: stage = SkRasterPipeline::screen; break;
106 case SkBlendMode::kOverlay: stage = SkRasterPipeline::overlay; break;
107 case SkBlendMode::kDarken: stage = SkRasterPipeline::darken; break;
108 case SkBlendMode::kLighten: stage = SkRasterPipeline::lighten; break;
109 case SkBlendMode::kColorDodge: stage = SkRasterPipeline::colordodge; break;
110 case SkBlendMode::kColorBurn: stage = SkRasterPipeline::colorburn; break;
111 case SkBlendMode::kHardLight: stage = SkRasterPipeline::hardlight; break;
112 case SkBlendMode::kSoftLight: stage = SkRasterPipeline::softlight; break;
113 case SkBlendMode::kDifference: stage = SkRasterPipeline::difference; break;
114 case SkBlendMode::kExclusion: stage = SkRasterPipeline::exclusion; break;
115 case SkBlendMode::kMultiply: stage = SkRasterPipeline::multiply; break;
116
117 case SkBlendMode::kHue: stage = SkRasterPipeline::hue; break;
118 case SkBlendMode::kSaturation: stage = SkRasterPipeline::saturation; break;
119 case SkBlendMode::kColor: stage = SkRasterPipeline::color; break;
120 case SkBlendMode::kLuminosity: stage = SkRasterPipeline::luminosity; break;
121 }
122 p->append(stage);
123}
124
125SkPMColor4f SkBlendMode_Apply(SkBlendMode mode, const SkPMColor4f& src, const SkPMColor4f& dst) {
126 // special-case simple/common modes...
127 switch (mode) {
128 case SkBlendMode::kClear: return SK_PMColor4fTRANSPARENT;
129 case SkBlendMode::kSrc: return src;
130 case SkBlendMode::kDst: return dst;
131 case SkBlendMode::kSrcOver: {
132 Sk4f r = Sk4f::Load(src.vec()) + Sk4f::Load(dst.vec()) * Sk4f(1 - src.fA);
133 return { r[0], r[1], r[2], r[3] };
134 }
135 default:
136 break;
137 }
138
139 SkRasterPipeline_<256> p;
140 SkPMColor4f src_storage = src,
141 dst_storage = dst,
142 res_storage;
143 SkRasterPipeline_MemoryCtx src_ctx = { &src_storage, 0 },
144 dst_ctx = { &dst_storage, 0 },
145 res_ctx = { &res_storage, 0 };
146
147 p.append(SkRasterPipeline::load_f32, &dst_ctx);
148 p.append(SkRasterPipeline::move_src_dst);
149 p.append(SkRasterPipeline::load_f32, &src_ctx);
150 SkBlendMode_AppendStages(mode, &p);
151 p.append(SkRasterPipeline::store_f32, &res_ctx);
152 p.run(0,0, 1,1);
153 return res_storage;
154}
155