1 /* 2 * Copyright (C) 2006 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef SkXfermode_DEFINED 18 #define SkXfermode_DEFINED 19 20 #include "SkFlattenable.h" 21 #include "SkColor.h" 22 23 /** \class SkXfermode 24 25 SkXfermode is the base class for objects that are called to implement custom 26 "transfer-modes" in the drawing pipeline. The static function Create(Modes) 27 can be called to return an instance of any of the predefined subclasses as 28 specified in the Modes enum. When an SkXfermode is assigned to an SkPaint, 29 then objects drawn with that paint have the xfermode applied. 30 */ 31 class SkXfermode : public SkFlattenable { 32 public: 33 SkXfermode() {} 34 35 virtual void xfer32(SkPMColor dst[], const SkPMColor src[], int count, 36 const SkAlpha aa[]); 37 virtual void xfer16(uint16_t dst[], const SkPMColor src[], int count, 38 const SkAlpha aa[]); 39 virtual void xfer4444(uint16_t dst[], const SkPMColor src[], int count, 40 const SkAlpha aa[]); 41 virtual void xferA8(SkAlpha dst[], const SkPMColor src[], int count, 42 const SkAlpha aa[]); 43 44 /** Enum of possible coefficients to describe some xfermodes 45 */ 46 enum Coeff { 47 kZero_Coeff, /** 0 */ 48 kOne_Coeff, /** 1 */ 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) */ 57 58 kCoeffCount 59 }; 60 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 63 dst accordingly. 64 65 result = src_coeff * src_color + dst_coeff * dst_color; 66 67 As examples, here are some of the porterduff coefficients 68 69 MODE SRC_COEFF DST_COEFF 70 clear zero zero 71 src one zero 72 dst zero one 73 srcover one isa 74 dstover ida one 75 */ 76 virtual bool asCoeff(Coeff* src, Coeff* dst); 77 78 /** List of predefined xfermodes. 79 The algebra for the modes uses the following symbols: 80 Sa, Sc - source alpha and color 81 Da, Dc - destination alpha and color (before compositing) 82 [a, c] - Resulting (alpha, color) values 83 For these equations, the colors are in premultiplied state. 84 If no xfermode is specified, kSrcOver is assumed. 85 */ 86 enum Mode { 87 kClear_Mode, //!< [0, 0] 88 kSrc_Mode, //!< [Sa, Sc] 89 kDst_Mode, //!< [Da, Dc] 90 kSrcOver_Mode, //!< [Sa + Da - Sa*Da, Rc = Sc + (1 - Sa)*Dc] 91 kDstOver_Mode, //!< [Sa + Da - Sa*Da, Rc = Dc + (1 - Da)*Sc] 92 kSrcIn_Mode, //!< [Sa * Da, Sc * Da] 93 kDstIn_Mode, //!< [Sa * Da, Sa * Dc] 94 kSrcOut_Mode, //!< [Sa * (1 - Da), Sc * (1 - Da)] 95 kDstOut_Mode, //!< [Da * (1 - Sa), Dc * (1 - Sa)] 96 kSrcATop_Mode, //!< [Da, Sc * Da + (1 - Sa) * Dc] 97 kDstATop_Mode, //!< [Sa, Sa * Dc + Sc * (1 - Da)] 98 kXor_Mode, //!< [Sa + Da - 2 * Sa * Da, Sc * (1 - Da) + (1 - Sa) * Dc] 99 100 // these modes are defined in the SVG Compositing standard 101 // http://www.w3.org/TR/2009/WD-SVGCompositing-20090430/ 102 kPlus_Mode, 103 kMultiply_Mode, 104 kScreen_Mode, 105 kOverlay_Mode, 106 kDarken_Mode, 107 kLighten_Mode, 108 kColorDodge_Mode, 109 kColorBurn_Mode, 110 kHardLight_Mode, 111 kSoftLight_Mode, 112 kDifference_Mode, 113 kExclusion_Mode, 114 115 kLastMode = kExclusion_Mode 116 }; 117 118 /** Return an SkXfermode object for the specified mode. 119 */ 120 static SkXfermode* Create(Mode mode); 121 122 /** Return a function pointer to a routine that applies the specified 123 porter-duff transfer mode. 124 */ 125 static SkXfermodeProc GetProc(Mode mode); 126 127 /** Return a function pointer to a routine that applies the specified 128 porter-duff transfer mode and srcColor to a 16bit device color. Note, 129 if the mode+srcColor might return a non-opaque color, then there is not 130 16bit proc, and this will return NULL. 131 */ 132 static SkXfermodeProc16 GetProc16(Mode mode, SkColor srcColor); 133 134 /** If the specified xfermode advertises itself as one of the porterduff 135 modes (via SkXfermode::Coeff), return true and if not null, set mode 136 to the corresponding porterduff mode. If it is not recognized as a one, 137 return false and ignore the mode parameter. 138 */ 139 static bool IsMode(SkXfermode*, Mode* mode); 140 141 protected: 142 SkXfermode(SkFlattenableReadBuffer& rb) : SkFlattenable(rb) {} 143 144 /** The default implementation of xfer32/xfer16/xferA8 in turn call this 145 method, 1 color at a time (upscaled to a SkPMColor). The default 146 implmentation of this method just returns dst. If performance is 147 important, your subclass should override xfer32/xfer16/xferA8 directly. 148 149 This method will not be called directly by the client, so it need not 150 be implemented if your subclass has overridden xfer32/xfer16/xferA8 151 */ 152 virtual SkPMColor xferColor(SkPMColor src, SkPMColor dst); 153 154 private: 155 enum { 156 kModeCount = kLastMode + 1 157 }; 158 typedef SkFlattenable INHERITED; 159 }; 160 161 /////////////////////////////////////////////////////////////////////////////// 162 163 /** \class SkProcXfermode 164 165 SkProcXfermode is a xfermode that applies the specified proc to its colors. 166 This class is not exported to java. 167 */ 168 class SkProcXfermode : public SkXfermode { 169 public: 170 SkProcXfermode(SkXfermodeProc proc) : fProc(proc) {} 171 172 // overrides from SkXfermode 173 virtual void xfer32(SkPMColor dst[], const SkPMColor src[], int count, 174 const SkAlpha aa[]); 175 virtual void xfer16(uint16_t dst[], const SkPMColor src[], int count, 176 const SkAlpha aa[]); 177 virtual void xfer4444(uint16_t dst[], const SkPMColor src[], int count, 178 const SkAlpha aa[]); 179 virtual void xferA8(SkAlpha dst[], const SkPMColor src[], int count, 180 const SkAlpha aa[]); 181 182 // overrides from SkFlattenable 183 virtual Factory getFactory() { return CreateProc; } 184 virtual void flatten(SkFlattenableWriteBuffer&); 185 186 protected: 187 SkProcXfermode(SkFlattenableReadBuffer&); 188 189 private: 190 SkXfermodeProc fProc; 191 192 static SkFlattenable* CreateProc(SkFlattenableReadBuffer& buffer) { 193 return SkNEW_ARGS(SkProcXfermode, (buffer)); } 194 195 typedef SkXfermode INHERITED; 196 }; 197 198 #endif 199 200
