unsigned offset = (alpha==kCGImageAlphaNoneSkipFirst);
CFRange range = CFRangeMake(offset, CFDataGetLength(image_data)-offset);
CFDataGetBytes(image_data, range, reinterpret_cast<UInt8 *>(data.pixels));
unsigned offset = (alpha==kCGImageAlphaNoneSkipFirst);
CFRange range = CFRangeMake(offset, CFDataGetLength(image_data)-offset);
CFDataGetBytes(image_data, range, reinterpret_cast<UInt8 *>(data.pixels));