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/*
* Copyright 2018 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "SkColorSpaceXformSteps.h"
// TODO: explain
SkColorSpaceXformSteps::SkColorSpaceXformSteps(SkColorSpace* src, SkAlphaType srcAT,
SkColorSpace* dst) {
// Set all bools to false, all floats to 0.0f.
memset(this, 0, sizeof(*this));
// We have some options about what to do with null src or dst here.
SkASSERT(src && dst);
this->flags.unpremul = srcAT == kPremul_SkAlphaType;
this->flags.linearize = !src->gammaIsLinear();
this->flags.gamut_transform = src->toXYZD50Hash() != dst->toXYZD50Hash();
this->flags.encode = !dst->gammaIsLinear();
this->flags.premul = srcAT != kOpaque_SkAlphaType;
if (this->flags.gamut_transform && src->toXYZD50() && dst->fromXYZD50()) {
auto xform = SkMatrix44(*dst->fromXYZD50(), *src->toXYZD50());
if (xform.get(3,0) == 0 && xform.get(3,1) == 0 && xform.get(3,2) == 0 &&
xform.get(3,3) == 1 &&
xform.get(0,3) == 0 && xform.get(1,3) == 0 && xform.get(2,3) == 0) {
for (int r = 0; r < 3; r++)
for (int c = 0; c < 3; c++) {
this->src_to_dst_matrix[3*c+r] = xform.get(r,c);
}
}
}
// Fill out all the transfer functions we'll use:
SkColorSpaceTransferFn srcTF, dstTF;
SkAssertResult(src->isNumericalTransferFn(&srcTF));
SkAssertResult(dst->isNumericalTransferFn(&dstTF));
this->srcTF = srcTF;
this->dstTFInv = dstTF.invert();
// If we linearize then immediately reencode with the same transfer function, skip both.
if ( this->flags.linearize &&
!this->flags.gamut_transform &&
this->flags.encode &&
0 == memcmp(&srcTF, &dstTF, sizeof(SkColorSpaceTransferFn)))
{
this->flags.linearize = false;
this->flags.encode = false;
}
// Skip unpremul...premul if there are no non-linear operations between.
if ( this->flags.unpremul &&
!this->flags.linearize &&
!this->flags.encode &&
this->flags.premul)
{
this->flags.unpremul = false;
this->flags.premul = false;
}
}
void SkColorSpaceXformSteps::apply(float* rgba) const {
if (flags.unpremul) {
float invA = isfinite(1.0f / rgba[3]) ? 1.0f / rgba[3] : 0;
rgba[0] *= invA;
rgba[1] *= invA;
rgba[2] *= invA;
}
if (flags.linearize) {
rgba[0] = srcTF(rgba[0]);
rgba[1] = srcTF(rgba[1]);
rgba[2] = srcTF(rgba[2]);
}
if (flags.gamut_transform) {
float temp[3] = { rgba[0], rgba[1], rgba[2] };
for (int i = 0; i < 3; ++i) {
rgba[i] = src_to_dst_matrix[ i] * temp[0] +
src_to_dst_matrix[3 + i] * temp[1] +
src_to_dst_matrix[6 + i] * temp[2];
}
}
if (flags.encode) {
rgba[0] = dstTFInv(rgba[0]);
rgba[1] = dstTFInv(rgba[1]);
rgba[2] = dstTFInv(rgba[2]);
}
if (flags.premul) {
rgba[0] *= rgba[3];
rgba[1] *= rgba[3];
rgba[2] *= rgba[3];
}
}
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