1 2 /* 3 * Copyright 2006 The Android Open Source Project 4 * 5 * Use of this source code is governed by a BSD-style license that can be 6 * found in the LICENSE file. 7 */ 8 9 10 #ifndef SkXfermode_DEFINED 11 #define SkXfermode_DEFINED 12 13 #include "SkFlattenable.h" 14 #include "SkColor.h" 15 16 class GrEffectRef; 17 class GrTexture; 18 class SkString; 19 20 /** \class SkXfermode 21 * 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. 27 * 28 * All subclasses are required to be reentrant-safe : it must be legal to share 29 * the same instance between several threads. 30 */ 31 class SK_API SkXfermode : public SkFlattenable { 32 public: 33 SK_DECLARE_INST_COUNT(SkXfermode) 34 35 virtual void xfer32(SkPMColor dst[], const SkPMColor src[], int count, 36 const SkAlpha aa[]) const; 37 virtual void xfer16(uint16_t dst[], const SkPMColor src[], int count, 38 const SkAlpha aa[]) const; 39 virtual void xferA8(SkAlpha dst[], const SkPMColor src[], int count, 40 const SkAlpha aa[]) const; 41 42 /** Enum of possible coefficients to describe some xfermodes 43 */ 44 enum Coeff { 45 kZero_Coeff, /** 0 */ 46 kOne_Coeff, /** 1 */ 47 kSC_Coeff, /** src color */ 48 kISC_Coeff, /** inverse src color (i.e. 1 - sc) */ 49 kDC_Coeff, /** dst color */ 50 kIDC_Coeff, /** inverse dst color (i.e. 1 - dc) */ 51 kSA_Coeff, /** src alpha */ 52 kISA_Coeff, /** inverse src alpha (i.e. 1 - sa) */ 53 kDA_Coeff, /** dst alpha */ 54 kIDA_Coeff, /** inverse dst alpha (i.e. 1 - da) */ 55 56 kCoeffCount 57 }; 58 59 /** If the xfermode can be expressed as an equation using the coefficients 60 in Coeff, then asCoeff() returns true, and sets (if not null) src and 61 dst accordingly. 62 63 result = src_coeff * src_color + dst_coeff * dst_color; 64 65 As examples, here are some of the porterduff coefficients 66 67 MODE SRC_COEFF DST_COEFF 68 clear zero zero 69 src one zero 70 dst zero one 71 srcover one isa 72 dstover ida one 73 */ 74 virtual bool asCoeff(Coeff* src, Coeff* dst) const; 75 76 /** 77 * The same as calling xfermode->asCoeff(..), except that this also checks 78 * if the xfermode is NULL, and if so, treats it as kSrcOver_Mode. 79 */ 80 static bool AsCoeff(const SkXfermode*, Coeff* src, Coeff* dst); 81 82 /** List of predefined xfermodes. 83 The algebra for the modes uses the following symbols: 84 Sa, Sc - source alpha and color 85 Da, Dc - destination alpha and color (before compositing) 86 [a, c] - Resulting (alpha, color) values 87 For these equations, the colors are in premultiplied state. 88 If no xfermode is specified, kSrcOver is assumed. 89 The modes are ordered by those that can be expressed as a pair of Coeffs, followed by those 90 that aren't Coeffs but have separable r,g,b computations, and finally 91 those that are not separable. 92 */ 93 enum Mode { 94 kClear_Mode, //!< [0, 0] 95 kSrc_Mode, //!< [Sa, Sc] 96 kDst_Mode, //!< [Da, Dc] 97 kSrcOver_Mode, //!< [Sa + Da - Sa*Da, Rc = Sc + (1 - Sa)*Dc] 98 kDstOver_Mode, //!< [Sa + Da - Sa*Da, Rc = Dc + (1 - Da)*Sc] 99 kSrcIn_Mode, //!< [Sa * Da, Sc * Da] 100 kDstIn_Mode, //!< [Sa * Da, Sa * Dc] 101 kSrcOut_Mode, //!< [Sa * (1 - Da), Sc * (1 - Da)] 102 kDstOut_Mode, //!< [Da * (1 - Sa), Dc * (1 - Sa)] 103 kSrcATop_Mode, //!< [Da, Sc * Da + (1 - Sa) * Dc] 104 kDstATop_Mode, //!< [Sa, Sa * Dc + Sc * (1 - Da)] 105 kXor_Mode, //!< [Sa + Da - 2 * Sa * Da, Sc * (1 - Da) + (1 - Sa) * Dc] 106 kPlus_Mode, //!< [Sa + Da, Sc + Dc] 107 kModulate_Mode, // multiplies all components (= alpha and color) 108 109 // Following blend modes are defined in the CSS Compositing standard: 110 // https://dvcs.w3.org/hg/FXTF/rawfile/tip/compositing/index.html#blending 111 kScreen_Mode, 112 kLastCoeffMode = kScreen_Mode, 113 114 kOverlay_Mode, 115 kDarken_Mode, 116 kLighten_Mode, 117 kColorDodge_Mode, 118 kColorBurn_Mode, 119 kHardLight_Mode, 120 kSoftLight_Mode, 121 kDifference_Mode, 122 kExclusion_Mode, 123 kMultiply_Mode, 124 kLastSeparableMode = kMultiply_Mode, 125 126 kHue_Mode, 127 kSaturation_Mode, 128 kColor_Mode, 129 kLuminosity_Mode, 130 kLastMode = kLuminosity_Mode 131 }; 132 133 /** 134 * Gets the name of the Mode as a string. 135 */ 136 static const char* ModeName(Mode); 137 138 /** 139 * If the xfermode is one of the modes in the Mode enum, then asMode() 140 * returns true and sets (if not null) mode accordingly. Otherwise it 141 * returns false and ignores the mode parameter. 142 */ 143 virtual bool asMode(Mode* mode) const; 144 145 /** 146 * The same as calling xfermode->asMode(mode), except that this also checks 147 * if the xfermode is NULL, and if so, treats it as kSrcOver_Mode. 148 */ 149 static bool AsMode(const SkXfermode*, Mode* mode); 150 151 /** 152 * Returns true if the xfermode claims to be the specified Mode. This works 153 * correctly even if the xfermode is NULL (which equates to kSrcOver.) Thus 154 * you can say this without checking for a null... 155 * 156 * If (SkXfermode::IsMode(paint.getXfermode(), 157 * SkXfermode::kDstOver_Mode)) { 158 * ... 159 * } 160 */ 161 static bool IsMode(const SkXfermode* xfer, Mode mode); 162 163 /** Return an SkXfermode object for the specified mode. 164 */ 165 static SkXfermode* Create(Mode mode); 166 167 /** Return a function pointer to a routine that applies the specified 168 porter-duff transfer mode. 169 */ 170 static SkXfermodeProc GetProc(Mode mode); 171 172 /** Return a function pointer to a routine that applies the specified 173 porter-duff transfer mode and srcColor to a 16bit device color. Note, 174 if the mode+srcColor might return a non-opaque color, then there is not 175 16bit proc, and this will return NULL. 176 */ 177 static SkXfermodeProc16 GetProc16(Mode mode, SkColor srcColor); 178 179 /** 180 * If the specified mode can be represented by a pair of Coeff, then return 181 * true and set (if not NULL) the corresponding coeffs. If the mode is 182 * not representable as a pair of Coeffs, return false and ignore the 183 * src and dst parameters. 184 */ 185 static bool ModeAsCoeff(Mode mode, Coeff* src, Coeff* dst); 186 187 SK_ATTR_DEPRECATED("use AsMode(...)") 188 static bool IsMode(const SkXfermode* xfer, Mode* mode) { 189 return AsMode(xfer, mode); 190 } 191 192 /** A subclass may implement this factory function to work with the GPU backend. It is legal 193 to call this with all params NULL to simply test the return value. If effect is non-NULL 194 then the xfermode may optionally allocate an effect to return and the caller as *effect. 195 The caller will install it and own a ref to it. Since the xfermode may or may not assign 196 *effect, the caller should set *effect to NULL beforehand. background specifies the 197 texture to use as the background for compositing, and should be accessed in the effect's 198 fragment shader. If NULL, the effect should request access to destination color 199 (setWillReadDstColor()), and use that in the fragment shader (builder->dstColor()). 200 */ 201 virtual bool asNewEffect(GrEffectRef** effect, GrTexture* background = NULL) const; 202 203 /** Returns true if the xfermode can be expressed as coeffs (src, dst), or as an effect 204 (effect). This helper calls the asCoeff() and asNewEffect() virtuals. If the xfermode is 205 NULL, it is treated as kSrcOver_Mode. It is legal to call this with all params NULL to 206 simply test the return value. effect, src, and dst must all be NULL or all non-NULL. 207 */ 208 static bool AsNewEffectOrCoeff(SkXfermode*, 209 GrEffectRef** effect, 210 Coeff* src, 211 Coeff* dst, 212 GrTexture* background = NULL); 213 214 SK_TO_STRING_PUREVIRT() 215 SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP() 216 SK_DEFINE_FLATTENABLE_TYPE(SkXfermode) 217 218 protected: 219 SkXfermode() {} 220 explicit SkXfermode(SkReadBuffer& rb) : SkFlattenable(rb) {} 221 222 /** The default implementation of xfer32/xfer16/xferA8 in turn call this 223 method, 1 color at a time (upscaled to a SkPMColor). The default 224 implmentation of this method just returns dst. If performance is 225 important, your subclass should override xfer32/xfer16/xferA8 directly. 226 227 This method will not be called directly by the client, so it need not 228 be implemented if your subclass has overridden xfer32/xfer16/xferA8 229 */ 230 virtual SkPMColor xferColor(SkPMColor src, SkPMColor dst) const; 231 232 private: 233 enum { 234 kModeCount = kLastMode + 1 235 }; 236 237 typedef SkFlattenable INHERITED; 238 }; 239 240 #endif 241
