3 * Copyright 2006 The Android Open Source Project
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
10 #ifndef SkXfermode_DEFINED
11 #define SkXfermode_DEFINED
13 #include "SkFlattenable.h"
22 * SkXfermode is the base class for objects that are called to implement custom
23 * "transfer-modes" in the drawing pipeline. The static function Create(Modes)
24 * can be called to return an instance of any of the predefined subclasses as
25 * specified in the Modes enum. When an SkXfermode is assigned to an SkPaint,
26 * then objects drawn with that paint have the xfermode applied.
28 * All subclasses are required to be reentrant-safe : it must be legal to share
29 * the same instance between several threads.
31 class SK_API SkXfermode : public SkFlattenable {
33 SK_DECLARE_INST_COUNT(SkXfermode)
37 virtual void xfer32(SkPMColor dst[], const SkPMColor src[], int count,
38 const SkAlpha aa[]) const;
39 virtual void xfer16(uint16_t dst[], const SkPMColor src[], int count,
40 const SkAlpha aa[]) const;
41 virtual void xferA8(SkAlpha dst[], const SkPMColor src[], int count,
42 const SkAlpha aa[]) const;
44 /** Enum of possible coefficients to describe some xfermodes
49 kSC_Coeff, /** src color */
50 kISC_Coeff, /** inverse src color (i.e. 1 - sc) */
51 kDC_Coeff, /** dst color */
52 kIDC_Coeff, /** inverse dst color (i.e. 1 - dc) */
53 kSA_Coeff, /** src alpha */
54 kISA_Coeff, /** inverse src alpha (i.e. 1 - sa) */
55 kDA_Coeff, /** dst alpha */
56 kIDA_Coeff, /** inverse dst alpha (i.e. 1 - da) */
61 /** If the xfermode can be expressed as an equation using the coefficients
62 in Coeff, then asCoeff() returns true, and sets (if not null) src and
65 result = src_coeff * src_color + dst_coeff * dst_color;
67 As examples, here are some of the porterduff coefficients
69 MODE SRC_COEFF DST_COEFF
76 virtual bool asCoeff(Coeff* src, Coeff* dst) const;
79 * The same as calling xfermode->asCoeff(..), except that this also checks
80 * if the xfermode is NULL, and if so, treats it as kSrcOver_Mode.
82 static bool AsCoeff(const SkXfermode*, Coeff* src, Coeff* dst);
84 /** List of predefined xfermodes.
85 The algebra for the modes uses the following symbols:
86 Sa, Sc - source alpha and color
87 Da, Dc - destination alpha and color (before compositing)
88 [a, c] - Resulting (alpha, color) values
89 For these equations, the colors are in premultiplied state.
90 If no xfermode is specified, kSrcOver is assumed.
91 The modes are ordered by those that can be expressed as a pair of Coeffs, followed by those
92 that aren't Coeffs but have separable r,g,b computations, and finally
93 those that are not separable.
96 kClear_Mode, //!< [0, 0]
97 kSrc_Mode, //!< [Sa, Sc]
98 kDst_Mode, //!< [Da, Dc]
99 kSrcOver_Mode, //!< [Sa + Da - Sa*Da, Rc = Sc + (1 - Sa)*Dc]
100 kDstOver_Mode, //!< [Sa + Da - Sa*Da, Rc = Dc + (1 - Da)*Sc]
101 kSrcIn_Mode, //!< [Sa * Da, Sc * Da]
102 kDstIn_Mode, //!< [Sa * Da, Sa * Dc]
103 kSrcOut_Mode, //!< [Sa * (1 - Da), Sc * (1 - Da)]
104 kDstOut_Mode, //!< [Da * (1 - Sa), Dc * (1 - Sa)]
105 kSrcATop_Mode, //!< [Da, Sc * Da + (1 - Sa) * Dc]
106 kDstATop_Mode, //!< [Sa, Sa * Dc + Sc * (1 - Da)]
107 kXor_Mode, //!< [Sa + Da - 2 * Sa * Da, Sc * (1 - Da) + (1 - Sa) * Dc]
108 kPlus_Mode, //!< [Sa + Da, Sc + Dc]
109 kModulate_Mode, // multiplies all components (= alpha and color)
111 // Following blend modes are defined in the CSS Compositing standard:
112 // https://dvcs.w3.org/hg/FXTF/rawfile/tip/compositing/index.html#blending
114 kLastCoeffMode = kScreen_Mode,
126 kLastSeparableMode = kMultiply_Mode,
132 kLastMode = kLuminosity_Mode
136 * Gets the name of the Mode as a string.
138 static const char* ModeName(Mode);
141 * If the xfermode is one of the modes in the Mode enum, then asMode()
142 * returns true and sets (if not null) mode accordingly. Otherwise it
143 * returns false and ignores the mode parameter.
145 virtual bool asMode(Mode* mode) const;
148 * The same as calling xfermode->asMode(mode), except that this also checks
149 * if the xfermode is NULL, and if so, treats it as kSrcOver_Mode.
151 static bool AsMode(const SkXfermode*, Mode* mode);
154 * Returns true if the xfermode claims to be the specified Mode. This works
155 * correctly even if the xfermode is NULL (which equates to kSrcOver.) Thus
156 * you can say this without checking for a null...
158 * If (SkXfermode::IsMode(paint.getXfermode(),
159 * SkXfermode::kDstOver_Mode)) {
163 static bool IsMode(const SkXfermode* xfer, Mode mode);
165 /** Return an SkXfermode object for the specified mode.
167 static SkXfermode* Create(Mode mode);
169 /** Return a function pointer to a routine that applies the specified
170 porter-duff transfer mode.
172 static SkXfermodeProc GetProc(Mode mode);
174 /** Return a function pointer to a routine that applies the specified
175 porter-duff transfer mode and srcColor to a 16bit device color. Note,
176 if the mode+srcColor might return a non-opaque color, then there is not
177 16bit proc, and this will return NULL.
179 static SkXfermodeProc16 GetProc16(Mode mode, SkColor srcColor);
182 * If the specified mode can be represented by a pair of Coeff, then return
183 * true and set (if not NULL) the corresponding coeffs. If the mode is
184 * not representable as a pair of Coeffs, return false and ignore the
185 * src and dst parameters.
187 static bool ModeAsCoeff(Mode mode, Coeff* src, Coeff* dst);
189 SK_ATTR_DEPRECATED("use AsMode(...)")
190 static bool IsMode(const SkXfermode* xfer, Mode* mode) {
191 return AsMode(xfer, mode);
194 /** A subclass may implement this factory function to work with the GPU backend. It is legal
195 to call this with all params NULL to simply test the return value. If effect is non-NULL
196 then the xfermode may optionally allocate an effect to return and the caller as *effect.
197 The caller will install it and own a ref to it. Since the xfermode may or may not assign
198 *effect, the caller should set *effect to NULL beforehand. background specifies the
199 texture to use as the background for compositing, and should be accessed in the effect's
200 fragment shader. If NULL, the effect should request access to destination color
201 (setWillReadDstColor()), and use that in the fragment shader (builder->dstColor()).
203 virtual bool asNewEffect(GrEffectRef** effect, GrTexture* background = NULL) const;
205 /** Returns true if the xfermode can be expressed as coeffs (src, dst), or as an effect
206 (effect). This helper calls the asCoeff() and asNewEffect() virtuals. If the xfermode is
207 NULL, it is treated as kSrcOver_Mode. It is legal to call this with all params NULL to
208 simply test the return value. effect, src, and dst must all be NULL or all non-NULL.
210 static bool AsNewEffectOrCoeff(SkXfermode*,
211 GrEffectRef** effect,
214 GrTexture* background = NULL);
216 SkDEVCODE(virtual void toString(SkString* str) const = 0;)
217 SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
218 SK_DEFINE_FLATTENABLE_TYPE(SkXfermode)
221 SkXfermode(SkReadBuffer& rb) : SkFlattenable(rb) {}
223 /** The default implementation of xfer32/xfer16/xferA8 in turn call this
224 method, 1 color at a time (upscaled to a SkPMColor). The default
225 implmentation of this method just returns dst. If performance is
226 important, your subclass should override xfer32/xfer16/xferA8 directly.
228 This method will not be called directly by the client, so it need not
229 be implemented if your subclass has overridden xfer32/xfer16/xferA8
231 virtual SkPMColor xferColor(SkPMColor src, SkPMColor dst) const;
235 kModeCount = kLastMode + 1
238 friend class SkGraphics;
241 typedef SkFlattenable INHERITED;
244 ///////////////////////////////////////////////////////////////////////////////
246 /** \class SkProcXfermode
248 SkProcXfermode is a xfermode that applies the specified proc to its colors.
249 This class is not exported to java.
251 class SkProcXfermode : public SkXfermode {
253 SkProcXfermode(SkXfermodeProc proc) : fProc(proc) {}
255 // overrides from SkXfermode
256 virtual void xfer32(SkPMColor dst[], const SkPMColor src[], int count,
257 const SkAlpha aa[]) const SK_OVERRIDE;
258 virtual void xfer16(uint16_t dst[], const SkPMColor src[], int count,
259 const SkAlpha aa[]) const SK_OVERRIDE;
260 virtual void xferA8(SkAlpha dst[], const SkPMColor src[], int count,
261 const SkAlpha aa[]) const SK_OVERRIDE;
263 SK_DEVELOPER_TO_STRING()
264 SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkProcXfermode)
267 SkProcXfermode(SkReadBuffer&);
268 virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
270 // allow subclasses to update this after we unflatten
271 void setProc(SkXfermodeProc proc) {
275 SkXfermodeProc getProc() const {
280 SkXfermodeProc fProc;
282 typedef SkXfermode INHERITED;