michael@0: /* -*- Mode: c++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #include "LayerUtils.h"
michael@0: #include "PremultiplyTables.h"
michael@0: #include "mozilla/Endian.h"
michael@0: 
michael@0: namespace mozilla {
michael@0: namespace layers {
michael@0: 
michael@0: using namespace mozilla::gfx;
michael@0: 
michael@0: static inline const uint8_t PremultiplyValue(uint8_t a, uint8_t v) {
michael@0:   return PremultiplyTable[a*256+v];
michael@0: }
michael@0: 
michael@0: static inline const uint8_t UnpremultiplyValue(uint8_t a, uint8_t v) {
michael@0:   return UnpremultiplyTable[a*256+v];
michael@0: }
michael@0: 
michael@0: #ifdef DEBUG
michael@0: static bool IsLittleEndian()
michael@0: {
michael@0:     // Violate strict aliasing, because violating strict aliasing is how
michael@0:     // we always pack and unpack between uint32_t and uint8_t[].
michael@0:     uint16_t testShort;
michael@0:     static const uint8_t testBytes[2] = { 0xAA, 0xBB };
michael@0:     memcpy(&testShort, testBytes, sizeof(testBytes));
michael@0:     return testShort == 0xBBAA;
michael@0: }
michael@0: #endif // DEBUG
michael@0: 
michael@0: #ifdef MOZ_LITTLE_ENDIAN
michael@0: #define ASSERT_ENDIAN() MOZ_ASSERT(IsLittleEndian(), "Defined as little endian, but actually big!")
michael@0: #else
michael@0: #define ASSERT_ENDIAN() MOZ_ASSERT(!IsLittleEndian(), "Defined as big endian, but actually little!")
michael@0: #endif
michael@0: 
michael@0: void
michael@0: PremultiplySurface(DataSourceSurface* srcSurface,
michael@0:                    DataSourceSurface* destSurface)
michael@0: {
michael@0:   if (!destSurface)
michael@0:     destSurface = srcSurface;
michael@0: 
michael@0:   IntSize srcSize = srcSurface->GetSize();
michael@0:   MOZ_ASSERT(srcSurface->GetFormat() == destSurface->GetFormat() &&
michael@0:              srcSize.width  == destSurface->GetSize().width &&
michael@0:              srcSize.height  == destSurface->GetSize().height &&
michael@0:              srcSurface->Stride() == destSurface->Stride(),
michael@0:              "Source and destination surfaces don't have identical characteristics");
michael@0: 
michael@0:   MOZ_ASSERT(srcSurface->Stride() == srcSize.width * 4,
michael@0:              "Source surface stride isn't tightly packed");
michael@0: 
michael@0:   // Only premultiply ARGB32
michael@0:   if (srcSurface->GetFormat() != SurfaceFormat::B8G8R8A8) {
michael@0:     if (destSurface != srcSurface) {
michael@0:       memcpy(destSurface->GetData(), srcSurface->GetData(),
michael@0:              srcSurface->Stride() * srcSize.height);
michael@0:     }
michael@0:     return;
michael@0:   }
michael@0: 
michael@0:   uint8_t *src = srcSurface->GetData();
michael@0:   uint8_t *dst = destSurface->GetData();
michael@0: 
michael@0:   // Assert that our endian define is correct.
michael@0:   ASSERT_ENDIAN();
michael@0: 
michael@0:   uint32_t dim = srcSize.width * srcSize.height;
michael@0:   for (uint32_t i = 0; i < dim; ++i) {
michael@0: #ifdef MOZ_LITTLE_ENDIAN
michael@0:     uint8_t b = *src++;
michael@0:     uint8_t g = *src++;
michael@0:     uint8_t r = *src++;
michael@0:     uint8_t a = *src++;
michael@0: 
michael@0:     *dst++ = PremultiplyValue(a, b);
michael@0:     *dst++ = PremultiplyValue(a, g);
michael@0:     *dst++ = PremultiplyValue(a, r);
michael@0:     *dst++ = a;
michael@0: #else
michael@0:     uint8_t a = *src++;
michael@0:     uint8_t r = *src++;
michael@0:     uint8_t g = *src++;
michael@0:     uint8_t b = *src++;
michael@0: 
michael@0:     *dst++ = a;
michael@0:     *dst++ = PremultiplyValue(a, r);
michael@0:     *dst++ = PremultiplyValue(a, g);
michael@0:     *dst++ = PremultiplyValue(a, b);
michael@0: #endif
michael@0:   }
michael@0: }
michael@0: 
michael@0: 
michael@0: }
michael@0: }