253 lines
9.6 KiB
C++
253 lines
9.6 KiB
C++
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/*
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* Copyright 2006 The Android Open Source Project
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkXfermode_DEFINED
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#define SkXfermode_DEFINED
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#include "SkFlattenable.h"
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#include "SkColor.h"
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class GrFragmentProcessor;
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class GrTexture;
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class GrXPFactory;
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class SkString;
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/** \class SkXfermode
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*
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* SkXfermode is the base class for objects that are called to implement custom
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* "transfer-modes" in the drawing pipeline. The static function Create(Modes)
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* can be called to return an instance of any of the predefined subclasses as
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* specified in the Modes enum. When an SkXfermode is assigned to an SkPaint,
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* then objects drawn with that paint have the xfermode applied.
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*
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* All subclasses are required to be reentrant-safe : it must be legal to share
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* the same instance between several threads.
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*/
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class SK_API SkXfermode : public SkFlattenable {
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public:
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virtual void xfer32(SkPMColor dst[], const SkPMColor src[], int count,
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const SkAlpha aa[]) const;
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virtual void xfer16(uint16_t dst[], const SkPMColor src[], int count,
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const SkAlpha aa[]) const;
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virtual void xferA8(SkAlpha dst[], const SkPMColor src[], int count,
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const SkAlpha aa[]) const;
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/** Enum of possible coefficients to describe some xfermodes
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*/
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enum Coeff {
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kZero_Coeff, /** 0 */
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kOne_Coeff, /** 1 */
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kSC_Coeff, /** src color */
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kISC_Coeff, /** inverse src color (i.e. 1 - sc) */
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kDC_Coeff, /** dst color */
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kIDC_Coeff, /** inverse dst color (i.e. 1 - dc) */
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kSA_Coeff, /** src alpha */
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kISA_Coeff, /** inverse src alpha (i.e. 1 - sa) */
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kDA_Coeff, /** dst alpha */
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kIDA_Coeff, /** inverse dst alpha (i.e. 1 - da) */
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kCoeffCount
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};
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/** List of predefined xfermodes.
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The algebra for the modes uses the following symbols:
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Sa, Sc - source alpha and color
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Da, Dc - destination alpha and color (before compositing)
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[a, c] - Resulting (alpha, color) values
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For these equations, the colors are in premultiplied state.
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If no xfermode is specified, kSrcOver is assumed.
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The modes are ordered by those that can be expressed as a pair of Coeffs, followed by those
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that aren't Coeffs but have separable r,g,b computations, and finally
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those that are not separable.
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*/
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enum Mode {
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kClear_Mode, //!< [0, 0]
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kSrc_Mode, //!< [Sa, Sc]
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kDst_Mode, //!< [Da, Dc]
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kSrcOver_Mode, //!< [Sa + Da * (1 - Sa), Sc + Dc * (1 - Sa)]
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kDstOver_Mode, //!< [Da + Sa * (1 - Da), Dc + Sc * (1 - Da)]
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kSrcIn_Mode, //!< [Sa * Da, Sc * Da]
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kDstIn_Mode, //!< [Da * Sa, Dc * Sa]
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kSrcOut_Mode, //!< [Sa * (1 - Da), Sc * (1 - Da)]
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kDstOut_Mode, //!< [Da * (1 - Sa), Dc * (1 - Sa)]
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kSrcATop_Mode, //!< [Da, Sc * Da + Dc * (1 - Sa)]
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kDstATop_Mode, //!< [Sa, Dc * Sa + Sc * (1 - Da)]
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kXor_Mode, //!< [Sa + Da - 2 * Sa * Da, Sc * (1 - Da) + Dc * (1 - Sa)]
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kPlus_Mode, //!< [Sa + Da, Sc + Dc]
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kModulate_Mode, // multiplies all components (= alpha and color)
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// Following blend modes are defined in the CSS Compositing standard:
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// https://dvcs.w3.org/hg/FXTF/rawfile/tip/compositing/index.html#blending
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kScreen_Mode,
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kLastCoeffMode = kScreen_Mode,
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kOverlay_Mode,
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kDarken_Mode,
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kLighten_Mode,
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kColorDodge_Mode,
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kColorBurn_Mode,
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kHardLight_Mode,
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kSoftLight_Mode,
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kDifference_Mode,
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kExclusion_Mode,
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kMultiply_Mode,
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kLastSeparableMode = kMultiply_Mode,
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kHue_Mode,
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kSaturation_Mode,
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kColor_Mode,
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kLuminosity_Mode,
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kLastMode = kLuminosity_Mode
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};
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/**
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* Gets the name of the Mode as a string.
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*/
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static const char* ModeName(Mode);
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/**
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* If the xfermode is one of the modes in the Mode enum, then asMode()
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* returns true and sets (if not null) mode accordingly. Otherwise it
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* returns false and ignores the mode parameter.
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*/
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virtual bool asMode(Mode* mode) const;
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/**
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* The same as calling xfermode->asMode(mode), except that this also checks
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* if the xfermode is NULL, and if so, treats it as kSrcOver_Mode.
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*/
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static bool AsMode(const SkXfermode*, Mode* mode);
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/**
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* Returns true if the xfermode claims to be the specified Mode. This works
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* correctly even if the xfermode is NULL (which equates to kSrcOver.) Thus
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* you can say this without checking for a null...
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*
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* If (SkXfermode::IsMode(paint.getXfermode(),
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* SkXfermode::kDstOver_Mode)) {
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* ...
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* }
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*/
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static bool IsMode(const SkXfermode* xfer, Mode mode);
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/** Return an SkXfermode object for the specified mode.
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*/
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static SkXfermode* Create(Mode mode);
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/** Return a function pointer to a routine that applies the specified
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porter-duff transfer mode.
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*/
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static SkXfermodeProc GetProc(Mode mode);
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/**
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* If the specified mode can be represented by a pair of Coeff, then return
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* true and set (if not NULL) the corresponding coeffs. If the mode is
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* not representable as a pair of Coeffs, return false and ignore the
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* src and dst parameters.
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*/
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static bool ModeAsCoeff(Mode mode, Coeff* src, Coeff* dst);
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SK_ATTR_DEPRECATED("use AsMode(...)")
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static bool IsMode(const SkXfermode* xfer, Mode* mode) {
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return AsMode(xfer, mode);
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}
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/**
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* Returns whether or not the xfer mode can support treating coverage as alpha
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*/
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virtual bool supportsCoverageAsAlpha() const;
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/**
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* The same as calling xfermode->supportsCoverageAsAlpha(), except that this also checks if
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* the xfermode is NULL, and if so, treats it as kSrcOver_Mode.
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*/
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static bool SupportsCoverageAsAlpha(const SkXfermode* xfer);
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enum SrcColorOpacity {
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// The src color is known to be opaque (alpha == 255)
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kOpaque_SrcColorOpacity = 0,
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// The src color is known to be fully transparent (color == 0)
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kTransparentBlack_SrcColorOpacity = 1,
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// The src alpha is known to be fully transparent (alpha == 0)
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kTransparentAlpha_SrcColorOpacity = 2,
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// The src color opacity is unknown
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kUnknown_SrcColorOpacity = 3
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};
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/**
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* Returns whether or not the result of the draw with the xfer mode will be opaque or not. The
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* input to this call is an enum describing known information about the opacity of the src color
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* that will be given to the xfer mode.
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*/
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virtual bool isOpaque(SrcColorOpacity opacityType) const;
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/**
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* The same as calling xfermode->isOpaque(...), except that this also checks if
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* the xfermode is NULL, and if so, treats it as kSrcOver_Mode.
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*/
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static bool IsOpaque(const SkXfermode* xfer, SrcColorOpacity opacityType);
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/** Used to do in-shader blending between two colors computed in the shader via a
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GrFragmentProcessor. The input to the returned FP is the src color. The dst color is
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provided by the dst param which becomes a child FP of the returned FP. If the params are
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null then this is just a query of whether the SkXfermode could support this functionality.
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It is legal for the function to succeed but return a null output. This indicates that
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the output of the blend is simply the src color.
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*/
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virtual bool asFragmentProcessor(const GrFragmentProcessor** output,
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const GrFragmentProcessor* dst) const;
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/** A subclass may implement this factory function to work with the GPU backend. It is legal
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to call this with xpf NULL to simply test the return value. If xpf is non-NULL then the
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xfermode may optionally allocate a factory to return to the caller as *xpf. The caller
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will install it and own a ref to it. Since the xfermode may or may not assign *xpf, the
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caller should set *xpf to NULL beforehand. XferProcessors cannot use a background texture.
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*/
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virtual bool asXPFactory(GrXPFactory** xpf) const;
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/** Returns true if the xfermode can be expressed as an xfer processor factory (xpFactory).
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This helper calls the asXPFactory() virtual. If the xfermode is NULL, it is treated as
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kSrcOver_Mode. It is legal to call this with xpf param NULL to simply test the return value.
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*/
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static inline bool AsXPFactory(SkXfermode* xfermode, GrXPFactory** xpf) {
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if (nullptr == xfermode) {
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if (xpf) {
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*xpf = nullptr;
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}
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return true;
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}
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return xfermode->asXPFactory(xpf);
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}
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SK_TO_STRING_PUREVIRT()
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SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
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SK_DEFINE_FLATTENABLE_TYPE(SkXfermode)
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protected:
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SkXfermode() {}
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/** The default implementation of xfer32/xfer16/xferA8 in turn call this
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method, 1 color at a time (upscaled to a SkPMColor). The default
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implementation of this method just returns dst. If performance is
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important, your subclass should override xfer32/xfer16/xferA8 directly.
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This method will not be called directly by the client, so it need not
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be implemented if your subclass has overridden xfer32/xfer16/xferA8
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*/
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virtual SkPMColor xferColor(SkPMColor src, SkPMColor dst) const;
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private:
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enum {
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kModeCount = kLastMode + 1
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};
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typedef SkFlattenable INHERITED;
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};
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#endif
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