reed@android.com | 8a1c16f | 2008-12-17 15:59:43 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright (C) 2008 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 | |
| 18 | |
| 19 | |
| 20 | #ifndef SkUnPreMultiply_DEFINED |
| 21 | #define SkUnPreMultiply_DEFINED |
| 22 | |
| 23 | #include "SkColor.h" |
| 24 | |
| 25 | class SkUnPreMultiply { |
| 26 | public: |
| 27 | typedef uint32_t Scale; |
| 28 | |
| 29 | // index this table with alpha [0..255] |
| 30 | static const Scale* GetScaleTable() { |
| 31 | return gTable; |
| 32 | } |
| 33 | |
| 34 | static Scale GetScale(U8CPU alpha) { |
| 35 | SkASSERT(alpha <= 255); |
| 36 | return gTable[alpha]; |
| 37 | } |
| 38 | |
| 39 | /** Usage: |
| 40 | |
| 41 | const Scale* table = SkUnPreMultiply::GetScaleTable(); |
| 42 | |
| 43 | for (...) { |
| 44 | unsigned a = ... |
| 45 | SkUnPreMultiply::Scale scale = table[a]; |
| 46 | |
| 47 | red = SkUnPreMultiply::ApplyScale(scale, red); |
| 48 | ... |
| 49 | // now red is unpremultiplied |
| 50 | } |
| 51 | */ |
| 52 | static U8CPU ApplyScale(Scale scale, U8CPU component) { |
| 53 | SkASSERT(component <= 255); |
| 54 | return (scale * component + (1 << 23)) >> 24; |
| 55 | } |
| 56 | |
| 57 | static SkColor PMColorToColor(SkPMColor c); |
| 58 | |
| 59 | private: |
| 60 | static const uint32_t gTable[256]; |
| 61 | }; |
| 62 | |
| 63 | #endif |