src/third_party/skia/src/gpu/effects/GrNonlinearColorSpaceXformEffect.h

/*
 * Copyright 2017 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef GrNonlinearColorSpaceXformEffect_DEFINED
#define GrNonlinearColorSpaceXformEffect_DEFINED

#include "GrFragmentProcessor.h"
#include "SkColorSpace.h"
#include "SkMatrix44.h"

/**
 * The output of this effect is the input, transformed into a different color space.
 * This effect is used for nonlinear blending color space support - it does not assume HW sRGB
 * capabilities, and performs both the source and destination transfer functions numerically in
 * the shader. Any parametric transfer function is supported. Because of the nonlinear blending,
 * premultiplication is also nonlinear - source pixels are unpremultiplied before the source
 * transfer function, and then premultiplied after the destination transfer function.
 */
class GrNonlinearColorSpaceXformEffect : public GrFragmentProcessor {
public:
    /**
     * The conversion effect is only well defined with a valid source and destination color space.
     * This will return nullptr if either space is nullptr, if both spaces are equal, or if either
     * space has a non-parametric transfer funcion (e.g. lookup table or A2B).
     */
    static sk_sp<GrFragmentProcessor> Make(const SkColorSpace* src, const SkColorSpace* dst);

    const char* name() const override { return "NonlinearColorSpaceXform"; }

    static const int kNumTransferFnCoeffs = 7;

    /**
     * Flags that specify which operations are performed for one particular conversion.
     * Some color space pairs may not need all operations, if one or both transfer functions
     * is linear, or if the gamuts are the same.
     */
    enum Ops {
        kSrcTransfer_Op = 0x1,
        kGamutXform_Op  = 0x2,
        kDstTransfer_Op = 0x4,
    };

    uint32_t ops() const { return fOps; }
    const float* srcTransferFnCoeffs() const { return fSrcTransferFnCoeffs; }
    const float* dstTransferFnCoeffs() const { return fDstTransferFnCoeffs; }
    const SkMatrix44& gamutXform() const { return fGamutXform; }

private:
    GrNonlinearColorSpaceXformEffect(uint32_t ops,
                                     const SkColorSpaceTransferFn& srcTransferFn,
                                     const SkColorSpaceTransferFn& dstTransferFn,
                                     const SkMatrix44& gamutXform);

    GrGLSLFragmentProcessor* onCreateGLSLInstance() const override;
    void onGetGLSLProcessorKey(const GrShaderCaps&, GrProcessorKeyBuilder*) const override;
    bool onIsEqual(const GrFragmentProcessor&) const override;

    float fSrcTransferFnCoeffs[kNumTransferFnCoeffs];
    float fDstTransferFnCoeffs[kNumTransferFnCoeffs];
    SkMatrix44 fGamutXform;
    uint32_t fOps;

    GR_DECLARE_FRAGMENT_PROCESSOR_TEST

    typedef GrFragmentProcessor INHERITED;
};

#endif