blob: de94bc6f86d45500194909f2ec1e211c6e4bc87e [file] [log] [blame]
/*
* 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 "src/core/SkColorSpaceXformSteps.h"
#include "include/core/SkColorSpace.h"
#include "include/core/SkTypes.h"
#include "include/private/base/SkFloatingPoint.h"
#include "modules/skcms/skcms.h"
#include "src/core/SkColorSpacePriv.h"
#include "src/core/SkRasterPipeline.h"
#include "src/core/SkVM.h"
// See skia.org/user/color (== site/user/color.md).
SkColorSpaceXformSteps::SkColorSpaceXformSteps(const SkColorSpace* src, SkAlphaType srcAT,
const SkColorSpace* dst, SkAlphaType dstAT) {
// Opaque outputs are treated as the same alpha type as the source input.
// TODO: we'd really like to have a good way of explaining why we think this is useful.
if (dstAT == kOpaque_SkAlphaType) {
dstAT = srcAT;
}
// We have some options about what to do with null src or dst here.
// This pair seems to be the most consistent with legacy expectations.
if (!src) { src = sk_srgb_singleton(); }
if (!dst) { dst = src; }
if (src->hash() == dst->hash() && srcAT == dstAT) {
SkASSERT(SkColorSpace::Equals(src,dst));
return;
}
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 && dstAT == kPremul_SkAlphaType;
if (this->flags.gamut_transform) {
skcms_Matrix3x3 src_to_dst; // TODO: switch src_to_dst_matrix to row-major
src->gamutTransformTo(dst, &src_to_dst);
this->src_to_dst_matrix[0] = src_to_dst.vals[0][0];
this->src_to_dst_matrix[1] = src_to_dst.vals[1][0];
this->src_to_dst_matrix[2] = src_to_dst.vals[2][0];
this->src_to_dst_matrix[3] = src_to_dst.vals[0][1];
this->src_to_dst_matrix[4] = src_to_dst.vals[1][1];
this->src_to_dst_matrix[5] = src_to_dst.vals[2][1];
this->src_to_dst_matrix[6] = src_to_dst.vals[0][2];
this->src_to_dst_matrix[7] = src_to_dst.vals[1][2];
this->src_to_dst_matrix[8] = src_to_dst.vals[2][2];
} else {
#ifdef SK_DEBUG
skcms_Matrix3x3 srcM, dstM;
src->toXYZD50(&srcM);
dst->toXYZD50(&dstM);
SkASSERT(0 == memcmp(&srcM, &dstM, 9*sizeof(float)) && "Hash collision");
#endif
}
// Fill out all the transfer functions we'll use.
src-> transferFn(&this->srcTF );
dst->invTransferFn(&this->dstTFInv);
// If we linearize then immediately reencode with the same transfer function, skip both.
if ( this->flags.linearize &&
!this->flags.gamut_transform &&
this->flags.encode &&
src->transferFnHash() == dst->transferFnHash())
{
#ifdef SK_DEBUG
skcms_TransferFunction dstTF;
dst->transferFn(&dstTF);
for (int i = 0; i < 7; i++) {
SkASSERT( (&srcTF.g)[i] == (&dstTF.g)[i] && "Hash collision" );
}
#endif
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) {
// I don't know why isfinite(x) stopped working on the Chromecast bots...
auto is_finite = [](float x) { return x*0 == 0; };
float invA = sk_ieee_float_divide(1.0f, rgba[3]);
invA = is_finite(invA) ? invA : 0;
rgba[0] *= invA;
rgba[1] *= invA;
rgba[2] *= invA;
}
if (flags.linearize) {
rgba[0] = skcms_TransferFunction_eval(&srcTF, rgba[0]);
rgba[1] = skcms_TransferFunction_eval(&srcTF, rgba[1]);
rgba[2] = skcms_TransferFunction_eval(&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] = skcms_TransferFunction_eval(&dstTFInv, rgba[0]);
rgba[1] = skcms_TransferFunction_eval(&dstTFInv, rgba[1]);
rgba[2] = skcms_TransferFunction_eval(&dstTFInv, rgba[2]);
}
if (flags.premul) {
rgba[0] *= rgba[3];
rgba[1] *= rgba[3];
rgba[2] *= rgba[3];
}
}
void SkColorSpaceXformSteps::apply(SkRasterPipeline* p) const {
if (flags.unpremul) { p->append(SkRasterPipelineOp::unpremul); }
if (flags.linearize) { p->append_transfer_function(srcTF); }
if (flags.gamut_transform) { p->append(SkRasterPipelineOp::matrix_3x3, &src_to_dst_matrix); }
if (flags.encode) { p->append_transfer_function(dstTFInv); }
if (flags.premul) { p->append(SkRasterPipelineOp::premul); }
}
skvm::F32 sk_program_transfer_fn(
skvm::F32 v, skcms_TFType tf_type,
skvm::F32 G, skvm::F32 A, skvm::F32 B, skvm::F32 C, skvm::F32 D, skvm::F32 E, skvm::F32 F)
{
// Strip off the sign bit and save it for later.
skvm::I32 bits = pun_to_I32(v),
sign = bits & 0x80000000;
v = pun_to_F32(bits ^ sign);
switch (tf_type) {
case skcms_TFType_Invalid: SkASSERT(false); break;
case skcms_TFType_sRGBish: {
v = select(v <= D, C*v + F
, approx_powf(A*v + B, G) + E);
} break;
case skcms_TFType_PQish: {
skvm::F32 vC = approx_powf(v, C);
v = approx_powf(max(B * vC + A, 0.0f) / (E * vC + D), F);
} break;
case skcms_TFType_HLGish: {
skvm::F32 vA = v*A,
K = F + 1.0f;
v = K*select(vA <= 1.0f, approx_powf(vA, B)
, approx_exp((v-E) * C + D));
} break;
case skcms_TFType_HLGinvish: {
skvm::F32 K = F + 1.0f;
v /= K;
v = select(v <= 1.0f, A * approx_powf(v, B)
, C * approx_log(v-D) + E);
} break;
}
// Re-apply the original sign bit on our way out the door.
return pun_to_F32(sign | pun_to_I32(v));
}
skvm::Color sk_program_transfer_fn(skvm::Builder* p, skvm::Uniforms* uniforms,
const skcms_TransferFunction& tf, skvm::Color c) {
skvm::F32 G = p->uniformF(uniforms->pushF(tf.g)),
A = p->uniformF(uniforms->pushF(tf.a)),
B = p->uniformF(uniforms->pushF(tf.b)),
C = p->uniformF(uniforms->pushF(tf.c)),
D = p->uniformF(uniforms->pushF(tf.d)),
E = p->uniformF(uniforms->pushF(tf.e)),
F = p->uniformF(uniforms->pushF(tf.f));
skcms_TFType tf_type = skcms_TransferFunction_getType(&tf);
return {
sk_program_transfer_fn(c.r, tf_type, G,A,B,C,D,E,F),
sk_program_transfer_fn(c.g, tf_type, G,A,B,C,D,E,F),
sk_program_transfer_fn(c.b, tf_type, G,A,B,C,D,E,F),
c.a,
};
}
skvm::Color SkColorSpaceXformSteps::program(skvm::Builder* p, skvm::Uniforms* uniforms,
skvm::Color c) const {
if (flags.unpremul) {
c = unpremul(c);
}
if (flags.linearize) {
c = sk_program_transfer_fn(p, uniforms, srcTF, c);
}
if (flags.gamut_transform) {
auto m = [&](int index) {
return p->uniformF(uniforms->pushF(src_to_dst_matrix[index]));
};
auto R = c.r * m(0) + c.g * m(3) + c.b * m(6),
G = c.r * m(1) + c.g * m(4) + c.b * m(7),
B = c.r * m(2) + c.g * m(5) + c.b * m(8);
c = {R, G, B, c.a};
}
if (flags.encode) {
c = sk_program_transfer_fn(p, uniforms, dstTFInv, c);
}
if (flags.premul) {
c = premul(c);
}
return c;
}