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* Copyright 2016 Google Inc.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#ifndef SkColorSpace_A2B_DEFINED
#define SkColorSpace_A2B_DEFINED
#include "SkColorSpace_Base.h"
#include <vector>
// An alternative SkColorSpace that represents all the color space data that
// is stored in an A2B0 ICC tag. This allows us to use alternative profile
// connection spaces (CIELAB instead of just CIEXYZ), use color-lookup-tables
// to do color space transformations not representable as TRC functions or
// matrix operations, as well as have multiple TRC functions. The CLUT also
// allows conversion between non-3-channel input color spaces ie CMYK(4) to
// a workable PCS (ie XYZ).
// AtoBType, lut8Type and lut16Type A2B0 tag types are supported. There are
// also MPET (multi-processing-elements) A2B0 tags in the standard which allow
// you to combine these 3 primitives (TRC, CLUT, matrix) in any order/quantity.
// MPET tags are currently unsupported by the MakeICC parser, could be supported
// here by the nature of the design.
class SkColorSpace_A2B : public SkColorSpace_Base {
const SkMatrix44* toXYZD50() const override {
// the matrix specified in A2B0 profiles is not necessarily
// a to-XYZ matrix, as to-Lab is supported as well so returning
// that could be misleading. Additionally, B-curves are applied
// after the matrix is, but a toXYZD50 matrix is the last thing
// applied in order to get into the (XYZ) profile connection space.
return nullptr;
uint32_t toXYZD50Hash() const override {
// See toXYZD50()'s comment.
return 0;
const SkMatrix44* fromXYZD50() const override {
// See toXYZD50()'s comment. Also, A2B0 profiles are not supported
// as destination color spaces, so an inverse matrix is never wanted.
return nullptr;
// There is no single gamma curve in an A2B0 profile
bool onGammaCloseToSRGB() const override { return false; }
bool onGammaIsLinear() const override { return false; }
bool onIsNumericalTransferFn(SkColorSpaceTransferFn* coeffs) const override { return false; }
bool onIsCMYK() const override { return kCMYK_ICCTypeFlag == fICCType; }
sk_sp<SkColorSpace> makeLinearGamma() const override {
// TODO: Analyze the extrema of our projection into XYZ and use suitable primaries?
// For now, just fall back to a default, because we don't have a good answer.
return SkColorSpace::MakeSRGBLinear();
sk_sp<SkColorSpace> makeSRGBGamma() const override {
// See comment in makeLinearGamma
return SkColorSpace::MakeSRGB();
Type type() const override { return Type::kA2B; }
class Element {
Element(SkGammaNamed gammaNamed, int channelCount)
: fType(Type::kGammaNamed)
, fGammaNamed(gammaNamed)
, fMatrix(SkMatrix44::kUninitialized_Constructor)
, fInputChannels(channelCount)
, fOutputChannels(channelCount) {
SkASSERT(gammaNamed != kNonStandard_SkGammaNamed);
explicit Element(sk_sp<SkGammas> gammas)
: fType(Type::kGammas)
, fGammas(std::move(gammas))
, fMatrix(SkMatrix44::kUninitialized_Constructor)
, fInputChannels(fGammas->channels())
, fOutputChannels(fGammas->channels()) {
for (int i = 0; i < fGammas->channels(); ++i) {
if (SkGammas::Type::kTable_Type == fGammas->type(i)) {
SkASSERT(fGammas->data(i).fTable.fSize >= 2);
explicit Element(sk_sp<SkColorLookUpTable> colorLUT)
: fType(Type::kCLUT)
, fCLUT(std::move(colorLUT))
, fMatrix(SkMatrix44::kUninitialized_Constructor)
, fInputChannels(fCLUT->inputChannels())
, fOutputChannels(fCLUT->outputChannels())
explicit Element(const SkMatrix44& matrix)
: fType(Type::kMatrix)
, fMatrix(matrix)
, fInputChannels(3)
, fOutputChannels(3)
enum class Type {
Type type() const { return fType; }
SkGammaNamed gammaNamed() const {
SkASSERT(Type::kGammaNamed == fType);
return fGammaNamed;
const SkGammas& gammas() const {
SkASSERT(Type::kGammas == fType);
return *fGammas;
const SkColorLookUpTable& colorLUT() const {
SkASSERT(Type::kCLUT == fType);
return *fCLUT;
const SkMatrix44& matrix() const {
SkASSERT(Type::kMatrix == fType);
return fMatrix;
int inputChannels() const { return fInputChannels; }
int outputChannels() const { return fOutputChannels; }
Type fType;
SkGammaNamed fGammaNamed;
sk_sp<SkGammas> fGammas;
sk_sp<SkColorLookUpTable> fCLUT;
SkMatrix44 fMatrix;
int fInputChannels;
int fOutputChannels;
const Element& element(int i) const { return fElements[i]; }
int count() const { return (int)fElements.size(); }
// the intermediate profile connection space that this color space
// represents the transformation to
enum class PCS : uint8_t {
PCS pcs() const { return fPCS; }
ICCTypeFlag iccType() const { return fICCType; }
SkColorSpace_A2B(ICCTypeFlag iccType, std::vector<Element> elements, PCS pcs,
sk_sp<SkData> profileData);
ICCTypeFlag fICCType;
std::vector<Element> fElements;
friend class SkColorSpace_Base;
friend class ColorSpaceXformTest;
typedef SkColorSpace_Base INHERITED;