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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 "SkBlendModePriv.h"
#include "SkCoverageModePriv.h"
#include "SkRasterPipeline.h"
#include "../jumper/SkJumper.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);
}
SkPM4f SkBlendMode_Apply(SkBlendMode mode, const SkPM4f& src, const SkPM4f& dst) {
// special-case simple/common modes...
switch (mode) {
case SkBlendMode::kClear: return {{ 0, 0, 0, 0 }};
case SkBlendMode::kSrc: return src;
case SkBlendMode::kDst: return dst;
case SkBlendMode::kSrcOver:
return SkPM4f::From4f(src.to4f() + dst.to4f() * Sk4f(1 - src.a()));
default:
break;
}
SkRasterPipeline_<256> p;
SkPM4f src_storage = src,
dst_storage = dst,
res_storage;
SkJumper_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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