// pre-conditions:
// - bottom and top image have the same size
// - bottom image format is ARGB32_Premultiplied
void IndependentChannelBlending::blend( QImage * const bottom,
TextureTile const * const top ) const
{
QImage const * const topImage = top->image();
Q_ASSERT( topImage );
Q_ASSERT( bottom->size() == topImage->size() );
Q_ASSERT( bottom->format() == QImage::Format_ARGB32_Premultiplied );
int const width = bottom->width();
int const height = bottom->height();
QImage const topImagePremult = topImage->convertToFormat( QImage::Format_ARGB32_Premultiplied );
for ( int y = 0; y < height; ++y ) {
for ( int x = 0; x < width; ++x ) {
QRgb const bottomPixel = bottom->pixel( x, y );
QRgb const topPixel = topImagePremult.pixel( x, y );
qreal const resultRed = blendChannel( qRed( bottomPixel ) / 255.0,
qRed( topPixel ) / 255.0 );
qreal const resultGreen = blendChannel( qGreen( bottomPixel ) / 255.0,
qGreen( topPixel ) / 255.0 );
qreal const resultBlue = blendChannel( qBlue( bottomPixel ) / 255.0,
qBlue( topPixel ) / 255.0 );
bottom->setPixel( x, y, qRgb( resultRed * 255.0,
resultGreen * 255.0,
resultBlue * 255.0 ));
}
}
}
inline uint32_t blendSrcOverDstNonPremultiplied(uint32_t src, uint32_t dst)
{
uint8_t srcA = SkGetPackedA32(src);
if (srcA == 0)
return dst;
uint8_t dstA = SkGetPackedA32(dst);
uint8_t dstFactorA = (dstA * SkAlpha255To256(255 - srcA)) >> 8;
ASSERT(srcA + dstFactorA < (1U << 8));
uint8_t blendA = srcA + dstFactorA;
unsigned scale = (1UL << 24) / blendA;
uint8_t blendR = blendChannel(SkGetPackedR32(src), srcA, SkGetPackedR32(dst), dstFactorA, scale);
uint8_t blendG = blendChannel(SkGetPackedG32(src), srcA, SkGetPackedG32(dst), dstFactorA, scale);
uint8_t blendB = blendChannel(SkGetPackedB32(src), srcA, SkGetPackedB32(dst), dstFactorA, scale);
return SkPackARGB32NoCheck(blendA, blendR, blendG, blendB);
}
