michael@0: 
michael@0: /*
michael@0:  * Copyright 2008 The Android Open Source Project
michael@0:  *
michael@0:  * Use of this source code is governed by a BSD-style license that can be
michael@0:  * found in the LICENSE file.
michael@0:  */
michael@0: 
michael@0: 
michael@0: 
michael@0: 
michael@0: 
michael@0: #ifndef SkUnPreMultiply_DEFINED
michael@0: #define SkUnPreMultiply_DEFINED
michael@0: 
michael@0: #include "SkColor.h"
michael@0: 
michael@0: class SK_API SkUnPreMultiply {
michael@0: public:
michael@0:     typedef uint32_t Scale;
michael@0: 
michael@0:     // index this table with alpha [0..255]
michael@0:     static const Scale* GetScaleTable() {
michael@0:         return gTable;
michael@0:     }
michael@0: 
michael@0:     static Scale GetScale(U8CPU alpha) {
michael@0:         SkASSERT(alpha <= 255);
michael@0:         return gTable[alpha];
michael@0:     }
michael@0: 
michael@0:     /** Usage:
michael@0: 
michael@0:         const Scale* table = SkUnPreMultiply::GetScaleTable();
michael@0: 
michael@0:         for (...) {
michael@0:             unsigned a = ...
michael@0:             SkUnPreMultiply::Scale scale = table[a];
michael@0: 
michael@0:             red = SkUnPreMultiply::ApplyScale(scale, red);
michael@0:             ...
michael@0:             // now red is unpremultiplied
michael@0:         }
michael@0:     */
michael@0:     static U8CPU ApplyScale(Scale scale, U8CPU component) {
michael@0:         SkASSERT(component <= 255);
michael@0:         return (scale * component + (1 << 23)) >> 24;
michael@0:     }
michael@0: 
michael@0:     static SkColor PMColorToColor(SkPMColor c);
michael@0: 
michael@0:     static uint32_t UnPreMultiplyPreservingByteOrder(SkPMColor c);
michael@0: 
michael@0: private:
michael@0:     static const uint32_t gTable[256];
michael@0: };
michael@0: 
michael@0: #endif