SkXfermode.h

/*
 * Copyright 2006 The Android Open Source Project
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkXfermode_DEFINED
#define SkXfermode_DEFINED

#include "SkFlattenable.h"
#include "SkColor.h"

class GrFragmentProcessor;
class GrTexture;
class GrXPFactory;
class SkRasterPipeline;
class SkString;

struct SkPM4f;
typedef SkPM4f (*SkXfermodeProc4f)(const SkPM4f& src, const SkPM4f& dst);

class SK_API SkXfermode : public SkFlattenable {
public:
    virtual void xfer32(SkPMColor dst[], const SkPMColor src[], int count,
                        const SkAlpha aa[]) const;
    virtual void xfer16(uint16_t dst[], const SkPMColor src[], int count,
                        const SkAlpha aa[]) const;
    virtual void xferA8(SkAlpha dst[], const SkPMColor src[], int count,
                        const SkAlpha aa[]) const;

    enum Coeff {
        kZero_Coeff,    
        kOne_Coeff,     
        kSC_Coeff,      
        kISC_Coeff,     
        kDC_Coeff,      
        kIDC_Coeff,     
        kSA_Coeff,      
        kISA_Coeff,     
        kDA_Coeff,      
        kIDA_Coeff,     
        kCoeffCount
    };

    enum Mode {
        kClear_Mode,    
        kSrc_Mode,      
        kDst_Mode,      
        kSrcOver_Mode,  
        kDstOver_Mode,  
        kSrcIn_Mode,    
        kDstIn_Mode,    
        kSrcOut_Mode,   
        kDstOut_Mode,   
        kSrcATop_Mode,  
        kDstATop_Mode,  
        kXor_Mode,      
        kPlus_Mode,     
        kModulate_Mode, // multiplies all components (= alpha and color)

        // Following blend modes are defined in the CSS Compositing standard:
        // https://dvcs.w3.org/hg/FXTF/rawfile/tip/compositing/index.html#blending
        kScreen_Mode,
        kLastCoeffMode = kScreen_Mode,

        kOverlay_Mode,
        kDarken_Mode,
        kLighten_Mode,
        kColorDodge_Mode,
        kColorBurn_Mode,
        kHardLight_Mode,
        kSoftLight_Mode,
        kDifference_Mode,
        kExclusion_Mode,
        kMultiply_Mode,
        kLastSeparableMode = kMultiply_Mode,

        kHue_Mode,
        kSaturation_Mode,
        kColor_Mode,
        kLuminosity_Mode,
        kLastMode = kLuminosity_Mode
    };

    static const char* ModeName(Mode);

    virtual bool asMode(Mode* mode) const;

    static bool AsMode(const SkXfermode*, Mode* mode);
    static bool AsMode(const sk_sp<SkXfermode>& xfer, Mode* mode) {
        return AsMode(xfer.get(), mode);
    }

    static bool IsMode(const SkXfermode* xfer, Mode mode);
    static bool IsMode(const sk_sp<SkXfermode>& xfer, Mode mode) {
        return IsMode(xfer.get(), mode);
    }

    static sk_sp<SkXfermode> Make(Mode);
#ifdef SK_SUPPORT_LEGACY_XFERMODE_PTR
    static SkXfermode* Create(Mode mode) {
        return Make(mode).release();
    }
    SK_ATTR_DEPRECATED("use AsMode(...)")
    static bool IsMode(const SkXfermode* xfer, Mode* mode) {
        return AsMode(xfer, mode);
    }
#endif

    static SkXfermodeProc GetProc(Mode mode);
    static SkXfermodeProc4f GetProc4f(Mode);

    virtual SkXfermodeProc4f getProc4f() const;

    bool appendStages(SkRasterPipeline*) const;

    static bool ModeAsCoeff(Mode mode, Coeff* src, Coeff* dst);

    virtual bool supportsCoverageAsAlpha() const;

    static bool SupportsCoverageAsAlpha(const SkXfermode* xfer);
    static bool SupportsCoverageAsAlpha(const sk_sp<SkXfermode>& xfer) {
        return SupportsCoverageAsAlpha(xfer.get());
    }

    enum SrcColorOpacity {
        // The src color is known to be opaque (alpha == 255)
        kOpaque_SrcColorOpacity = 0,
        // The src color is known to be fully transparent (color == 0)
        kTransparentBlack_SrcColorOpacity = 1,
        // The src alpha is known to be fully transparent (alpha == 0)
        kTransparentAlpha_SrcColorOpacity = 2,
        // The src color opacity is unknown
        kUnknown_SrcColorOpacity = 3
    };

    virtual bool isOpaque(SrcColorOpacity opacityType) const;

    static bool IsOpaque(const SkXfermode* xfer, SrcColorOpacity opacityType);
    static bool IsOpaque(const sk_sp<SkXfermode>& xfer, SrcColorOpacity opacityType) {
        return IsOpaque(xfer.get(), opacityType);
    }

#if SK_SUPPORT_GPU

    virtual sk_sp<GrFragmentProcessor> makeFragmentProcessorForImageFilter(
                                                            sk_sp<GrFragmentProcessor> dst) const;

    virtual sk_sp<GrXPFactory> asXPFactory() const;
#endif

    SK_TO_STRING_PUREVIRT()
    SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
    SK_DEFINE_FLATTENABLE_TYPE(SkXfermode)

    enum D32Flags {
        kSrcIsOpaque_D32Flag  = 1 << 0,
        kSrcIsSingle_D32Flag  = 1 << 1,
        kDstIsSRGB_D32Flag    = 1 << 2,
    };
    typedef void (*D32Proc)(const SkXfermode*, uint32_t dst[], const SkPM4f src[],
                            int count, const SkAlpha coverage[]);
    static D32Proc GetD32Proc(SkXfermode*, uint32_t flags);
    static D32Proc GetD32Proc(const sk_sp<SkXfermode>& xfer, uint32_t flags) {
        return GetD32Proc(xfer.get(), flags);
    }

    enum F16Flags {
        kSrcIsOpaque_F16Flag  = 1 << 0,
        kSrcIsSingle_F16Flag  = 1 << 1,
    };
    typedef void (*F16Proc)(const SkXfermode*, uint64_t dst[], const SkPM4f src[], int count,
                            const SkAlpha coverage[]);
    static F16Proc GetF16Proc(SkXfermode*, uint32_t flags);
    static F16Proc GetF16Proc(const sk_sp<SkXfermode>& xfer, uint32_t flags) {
        return GetF16Proc(xfer.get(), flags);
    }

    enum LCDFlags {
        kSrcIsOpaque_LCDFlag    = 1 << 0,   // else src(s) may have alpha < 1
        kSrcIsSingle_LCDFlag    = 1 << 1,   // else src[count]
        kDstIsSRGB_LCDFlag      = 1 << 2,   // else l32 or f16
    };
    typedef void (*LCD32Proc)(uint32_t* dst, const SkPM4f* src, int count, const uint16_t lcd[]);
    typedef void (*LCDF16Proc)(uint64_t* dst, const SkPM4f* src, int count, const uint16_t lcd[]);
    static LCD32Proc GetLCD32Proc(uint32_t flags);
    static LCDF16Proc GetLCDF16Proc(uint32_t) { return nullptr; }

protected:
    SkXfermode() {}
    virtual SkPMColor xferColor(SkPMColor src, SkPMColor dst) const;

    virtual D32Proc onGetD32Proc(uint32_t flags) const;
    virtual F16Proc onGetF16Proc(uint32_t flags) const;
    virtual bool onAppendStages(SkRasterPipeline*) const;

private:
    enum {
        kModeCount = kLastMode + 1
    };

    typedef SkFlattenable INHERITED;
};

#endif