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- /*
- * Copyright 2017 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
- #include "src/core/SkBlendModePriv.h"
- #include "src/core/SkCoverageModePriv.h"
- #include "src/core/SkRasterPipeline.h"
- bool SkBlendMode_ShouldPreScaleCoverage(SkBlendMode mode, bool rgb_coverage) {
- // The most important things we do here are:
- // 1) never pre-scale with rgb coverage if the blend mode involves a source-alpha term;
- // 2) always pre-scale Plus.
- //
- // When we pre-scale with rgb coverage, we scale each of source r,g,b, with a distinct value,
- // and source alpha with one of those three values. This process destructively updates the
- // source-alpha term, so we can't evaluate blend modes that need its original value.
- //
- // Plus always requires pre-scaling as a specific quirk of its implementation in
- // SkRasterPipeline. This lets us put the clamp inside the blend mode itself rather
- // than as a separate stage that'd come after the lerp.
- //
- // This function is a finer-grained breakdown of SkBlendMode_SupportsCoverageAsAlpha().
- switch (mode) {
- case SkBlendMode::kDst: // d --> no sa term, ok!
- case SkBlendMode::kDstOver: // d + s*inv(da) --> no sa term, ok!
- case SkBlendMode::kPlus: // clamp(s+d) --> no sa term, ok!
- return true;
- case SkBlendMode::kDstOut: // d * inv(sa)
- case SkBlendMode::kSrcATop: // s*da + d*inv(sa)
- case SkBlendMode::kSrcOver: // s + d*inv(sa)
- case SkBlendMode::kXor: // s*inv(da) + d*inv(sa)
- return !rgb_coverage;
- default: break;
- }
- return false;
- }
- // Users of this function may want to switch to the rgb-coverage aware version above.
- bool SkBlendMode_SupportsCoverageAsAlpha(SkBlendMode mode) {
- return SkBlendMode_ShouldPreScaleCoverage(mode, false);
- }
- struct CoeffRec {
- SkBlendModeCoeff fSrc;
- SkBlendModeCoeff fDst;
- };
- const CoeffRec gCoeffs[] = {
- { SkBlendModeCoeff::kZero, SkBlendModeCoeff::kZero },
- { SkBlendModeCoeff::kOne, SkBlendModeCoeff::kZero },
- { SkBlendModeCoeff::kZero, SkBlendModeCoeff::kOne },
- { SkBlendModeCoeff::kOne, SkBlendModeCoeff::kISA },
- { SkBlendModeCoeff::kIDA, SkBlendModeCoeff::kOne },
- { SkBlendModeCoeff::kDA, SkBlendModeCoeff::kZero },
- { SkBlendModeCoeff::kZero, SkBlendModeCoeff::kSA },
- { SkBlendModeCoeff::kIDA, SkBlendModeCoeff::kZero },
- { SkBlendModeCoeff::kZero, SkBlendModeCoeff::kISA },
- { SkBlendModeCoeff::kDA, SkBlendModeCoeff::kISA },
- { SkBlendModeCoeff::kIDA, SkBlendModeCoeff::kSA },
- { SkBlendModeCoeff::kIDA, SkBlendModeCoeff::kISA },
- { SkBlendModeCoeff::kOne, SkBlendModeCoeff::kOne },
- { SkBlendModeCoeff::kZero, SkBlendModeCoeff::kSC },
- { SkBlendModeCoeff::kOne, SkBlendModeCoeff::kISC }, // screen
- };
- bool SkBlendMode_AsCoeff(SkBlendMode mode, SkBlendModeCoeff* src, SkBlendModeCoeff* dst) {
- if (mode > SkBlendMode::kScreen) {
- return false;
- }
- if (src) {
- *src = gCoeffs[static_cast<int>(mode)].fSrc;
- }
- if (dst) {
- *dst = gCoeffs[static_cast<int>(mode)].fDst;
- }
- return true;
- }
- void SkBlendMode_AppendStages(SkBlendMode mode, SkRasterPipeline* p) {
- auto stage = SkRasterPipeline::srcover;
- switch (mode) {
- case SkBlendMode::kClear: stage = SkRasterPipeline::clear; break;
- case SkBlendMode::kSrc: return; // This stage is a no-op.
- case SkBlendMode::kDst: stage = SkRasterPipeline::move_dst_src; break;
- case SkBlendMode::kSrcOver: stage = SkRasterPipeline::srcover; break;
- case SkBlendMode::kDstOver: stage = SkRasterPipeline::dstover; break;
- case SkBlendMode::kSrcIn: stage = SkRasterPipeline::srcin; break;
- case SkBlendMode::kDstIn: stage = SkRasterPipeline::dstin; break;
- case SkBlendMode::kSrcOut: stage = SkRasterPipeline::srcout; break;
- case SkBlendMode::kDstOut: stage = SkRasterPipeline::dstout; break;
- case SkBlendMode::kSrcATop: stage = SkRasterPipeline::srcatop; break;
- case SkBlendMode::kDstATop: stage = SkRasterPipeline::dstatop; break;
- case SkBlendMode::kXor: stage = SkRasterPipeline::xor_; break;
- case SkBlendMode::kPlus: stage = SkRasterPipeline::plus_; break;
- case SkBlendMode::kModulate: stage = SkRasterPipeline::modulate; break;
- case SkBlendMode::kScreen: stage = SkRasterPipeline::screen; break;
- case SkBlendMode::kOverlay: stage = SkRasterPipeline::overlay; break;
- case SkBlendMode::kDarken: stage = SkRasterPipeline::darken; break;
- case SkBlendMode::kLighten: stage = SkRasterPipeline::lighten; break;
- case SkBlendMode::kColorDodge: stage = SkRasterPipeline::colordodge; break;
- case SkBlendMode::kColorBurn: stage = SkRasterPipeline::colorburn; break;
- case SkBlendMode::kHardLight: stage = SkRasterPipeline::hardlight; break;
- case SkBlendMode::kSoftLight: stage = SkRasterPipeline::softlight; break;
- case SkBlendMode::kDifference: stage = SkRasterPipeline::difference; break;
- case SkBlendMode::kExclusion: stage = SkRasterPipeline::exclusion; break;
- case SkBlendMode::kMultiply: stage = SkRasterPipeline::multiply; break;
- case SkBlendMode::kHue: stage = SkRasterPipeline::hue; break;
- case SkBlendMode::kSaturation: stage = SkRasterPipeline::saturation; break;
- case SkBlendMode::kColor: stage = SkRasterPipeline::color; break;
- case SkBlendMode::kLuminosity: stage = SkRasterPipeline::luminosity; break;
- }
- p->append(stage);
- }
- SkPMColor4f SkBlendMode_Apply(SkBlendMode mode, const SkPMColor4f& src, const SkPMColor4f& dst) {
- // special-case simple/common modes...
- switch (mode) {
- case SkBlendMode::kClear: return SK_PMColor4fTRANSPARENT;
- case SkBlendMode::kSrc: return src;
- case SkBlendMode::kDst: return dst;
- case SkBlendMode::kSrcOver: {
- Sk4f r = Sk4f::Load(src.vec()) + Sk4f::Load(dst.vec()) * Sk4f(1 - src.fA);
- return { r[0], r[1], r[2], r[3] };
- }
- default:
- break;
- }
- SkRasterPipeline_<256> p;
- SkPMColor4f src_storage = src,
- dst_storage = dst,
- res_storage;
- SkRasterPipeline_MemoryCtx src_ctx = { &src_storage, 0 },
- dst_ctx = { &dst_storage, 0 },
- res_ctx = { &res_storage, 0 };
- p.append(SkRasterPipeline::load_f32, &dst_ctx);
- p.append(SkRasterPipeline::move_src_dst);
- p.append(SkRasterPipeline::load_f32, &src_ctx);
- SkBlendMode_AppendStages(mode, &p);
- p.append(SkRasterPipeline::store_f32, &res_ctx);
- p.run(0,0, 1,1);
- return res_storage;
- }
- ///////////////////////////////////////////////////////////////////////////////////////////////////
- const SkBlendMode gUncorrelatedCoverageToBlend[] = {
- SkBlendMode::kSrcOver, // or DstOver
- SkBlendMode::kSrcIn, // or kDstIn
- SkBlendMode::kSrcOut,
- SkBlendMode::kDstOut,
- SkBlendMode::kXor,
- };
- SkBlendMode SkUncorrelatedCoverageModeToBlendMode(SkCoverageMode cm) {
- unsigned index = static_cast<unsigned>(cm);
- SkASSERT(index < SK_ARRAY_COUNT(gUncorrelatedCoverageToBlend));
- return gUncorrelatedCoverageToBlend[index];
- }
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