reed@android.com | 8a1c16f | 2008-12-17 15:59:43 +0000 | [diff] [blame^] | 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 | |