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Diffstat (limited to 'gfx/skia/skia/include/core/SkUnPreMultiply.h')
-rw-r--r-- | gfx/skia/skia/include/core/SkUnPreMultiply.h | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/gfx/skia/skia/include/core/SkUnPreMultiply.h b/gfx/skia/skia/include/core/SkUnPreMultiply.h new file mode 100644 index 0000000000..b492619d07 --- /dev/null +++ b/gfx/skia/skia/include/core/SkUnPreMultiply.h @@ -0,0 +1,56 @@ + +/* + * Copyright 2008 The Android Open Source Project + * + * Use of this source code is governed by a BSD-style license that can be + * found in the LICENSE file. + */ + + + + + +#ifndef SkUnPreMultiply_DEFINED +#define SkUnPreMultiply_DEFINED + +#include "include/core/SkColor.h" + +class SK_API SkUnPreMultiply { +public: + typedef uint32_t Scale; + + // index this table with alpha [0..255] + static const Scale* GetScaleTable() { + return gTable; + } + + static Scale GetScale(U8CPU alpha) { + SkASSERT(alpha <= 255); + return gTable[alpha]; + } + + /** Usage: + + const Scale* table = SkUnPreMultiply::GetScaleTable(); + + for (...) { + unsigned a = ... + SkUnPreMultiply::Scale scale = table[a]; + + red = SkUnPreMultiply::ApplyScale(scale, red); + ... + // now red is unpremultiplied + } + */ + static U8CPU ApplyScale(Scale scale, U8CPU component) { + SkASSERT(component <= 255); + return (scale * component + (1 << 23)) >> 24; + } + + static SkColor PMColorToColor(SkPMColor c); + +private: + static const uint32_t gTable[256]; +}; + +#endif |