void colorizeImage( QImage & grayImage, const QColor & color, unsigned int destAlpha )
{
// Make sure that the image is Format_ARGB32_Premultiplied
if ( grayImage.format() != QImage::Format_ARGB32_Premultiplied )
grayImage = grayImage.convertToFormat( QImage::Format_ARGB32_Premultiplied );
// iterate over all pixels changing the alpha component value
unsigned int * data = (unsigned int *)grayImage.bits();
unsigned int pixels = grayImage.width() * grayImage.height();
int red = color.red(),
green = color.green(),
blue = color.blue();
int source, sourceSat, sourceAlpha;
for( unsigned int i = 0; i < pixels; ++i )
{ // optimize this loop keeping byte order into account
source = data[i];
sourceSat = qRed( source );
int newR = qt_div_255( sourceSat * red ),
newG = qt_div_255( sourceSat * green ),
newB = qt_div_255( sourceSat * blue );
if ( (sourceAlpha = qAlpha( source )) == 255 )
{
// use destAlpha
data[i] = qRgba( newR, newG, newB, destAlpha );
}
else
{
// use destAlpha * sourceAlpha product
if ( destAlpha < 255 )
sourceAlpha = qt_div_255( destAlpha * sourceAlpha );
data[i] = qRgba( newR, newG, newB, sourceAlpha );
}
}
}
void forceSetAlphaChannel(QImage &image, const QImage &alphaChannel)
{
int w = image.width();
int h = image.height();
if (w != alphaChannel.width() || h != alphaChannel.height()) {
qWarning("forceSetAlphaChannel: "
"Alpha channel must have same dimensions as the target image");
return;
}
const QImage sourceImage = alphaChannel.convertToFormat(QImage::Format_RGB32);
const uchar *src_data = sourceImage.bits();
const uchar *dest_data = image.bits();
for (int y=0; y<h; ++y)
{
const QRgb *src = (const QRgb *) src_data;
QRgb *dest = (QRgb *) dest_data;
for (int x=0; x<w; ++x)
{
int alpha = qGray(*src);
int destAlpha = qt_div_255(alpha * 255); //qAlpha(*dest));
*dest = ((destAlpha << 24)
| (qt_div_255(qRed(*dest) * alpha) << 16)
| (qt_div_255(qGreen(*dest) * alpha) << 8)
| (qt_div_255(qBlue(*dest) * alpha)));
++dest;
++src;
}
src_data += sourceImage.bytesPerLine();
dest_data += image.bytesPerLine();
}
}
