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 SkPorterDuff_DEFINED 18 #define SkPorterDuff_DEFINED 19 20 #include "SkColor.h" 21 22 class SkXfermode; 23 24 class SkPorterDuff { 25 public: 26 /** List of predefined xfermodes. In general, the algebra for the modes 27 uses the following symbols: 28 Sa, Sc - source alpha and color 29 Da, Dc - destination alpha and color (before compositing) 30 [a, c] - Resulting (alpha, color) values 31 For these equations, the colors are in premultiplied state. 32 If no xfermode is specified, kSrcOver is assumed. 33 */ 34 enum Mode { 35 kClear_Mode, //!< [0, 0] 36 kSrc_Mode, //!< [Sa, Sc] 37 kDst_Mode, //!< [Da, Dc] 38 kSrcOver_Mode, //!< [Sa + Da - Sa*Da, Rc = Sc + (1 - Sa)*Dc] 39 kDstOver_Mode, //!< [Sa + Da - Sa*Da, Rc = Dc + (1 - Da)*Sc] 40 kSrcIn_Mode, //!< [Sa * Da, Sc * Da] 41 kDstIn_Mode, //!< [Sa * Da, Sa * Dc] 42 kSrcOut_Mode, //!< [Sa * (1 - Da), Sc * (1 - Da)] 43 kDstOut_Mode, //!< [Da * (1 - Sa), Dc * (1 - Sa)] 44 kSrcATop_Mode, //!< [Da, Sc * Da + (1 - Sa) * Dc] 45 kDstATop_Mode, //!< [Sa, Sa * Dc + Sc * (1 - Da)] 46 kXor_Mode, //!< [Sa + Da - 2 * Sa * Da, Sc * (1 - Da) + (1 - Sa) * Dc] 47 kDarken_Mode, //!< [Sa + Da - Sa*Da, Sc*(1 - Da) + Dc*(1 - Sa) + min(Sc, Dc)] 48 kLighten_Mode, //!< [Sa + Da - Sa*Da, Sc*(1 - Da) + Dc*(1 - Sa) + max(Sc, Dc)] 49 kMultiply_Mode, //!< [Sa * Da, Sc * Dc] 50 kScreen_Mode, //!< [Sa + Da - Sa * Da, Sc + Dc - Sc * Dc] 51 52 kModeCount 53 }; 54 /** Return an SkXfermode object for the specified mode. 55 */ 56 static SkXfermode* CreateXfermode(Mode mode); 57 58 /** Return a function pointer to a routine that applies the specified 59 porter-duff transfer mode. 60 */ 61 static SkXfermodeProc GetXfermodeProc(Mode mode); 62 63 /** Return a function pointer to a routine that applies the specified 64 porter-duff transfer mode and srcColor to a 16bit device color. Note, 65 if the mode+srcColor might return a non-opaque color, then there is not 66 16bit proc, and this will return NULL. 67 */ 68 static SkXfermodeProc16 GetXfermodeProc16(Mode mode, SkColor srcColor); 69 70 /** If the specified xfermode advertises itself as one of the porterduff 71 modes (via SkXfermode::Coeff), return true and if not null, set mode 72 to the corresponding porterduff mode. If it is not recognized as a one, 73 return false and ignore the mode parameter. 74 */ 75 static bool IsMode(SkXfermode*, Mode* mode); 76 }; 77 78 #endif 79 80