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Merge pull request #299 from Reflejo/master 

Fix "Alpha on JPEG with no alpha" when decoding
This commit is contained in:
Olivier Poitrey 2013-02-16 10:41:14 -08:00
parent b27d5719c2 de19c24241
commit 5f535602f1
1 changed files with 35 additions and 2 deletions
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37
SDWebImage/SDWebImageDecoder.m
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@ -18,8 +18,41 @@
CGSize imageSize = CGSizeMake(CGImageGetWidth(imageRef), CGImageGetHeight(imageRef));
CGRect imageRect = (CGRect){.origin = CGPointZero, .size = imageSize};
CGColorSpaceRef colorSpace = CGImageGetColorSpace(imageRef);
CGContextRef context = CGBitmapContextCreate(NULL, imageSize.width, imageSize.height, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpace, CGImageGetBitmapInfo(imageRef));
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
int infoMask = (bitmapInfo & kCGBitmapAlphaInfoMask);
BOOL anyNonAlpha = (infoMask == kCGImageAlphaNone ||
infoMask == kCGImageAlphaNoneSkipFirst ||
infoMask == kCGImageAlphaNoneSkipLast);
// CGBitmapContextCreate doesn't support kCGImageAlphaNone with RGB.
// https://developer.apple.com/library/mac/#qa/qa1037/_index.html
if (infoMask == kCGImageAlphaNone && CGColorSpaceGetNumberOfComponents(colorSpace) > 1)
{
// Unset the old alpha info.
bitmapInfo &= ~kCGBitmapAlphaInfoMask;
// Set noneSkipFirst.
bitmapInfo |= kCGImageAlphaNoneSkipFirst;
}
// Some PNGs tell us they have alpha but only 3 components. Odd.
else if (!anyNonAlpha && CGColorSpaceGetNumberOfComponents(colorSpace) == 3)
{
// Unset the old alpha info.
bitmapInfo &= ~kCGBitmapAlphaInfoMask;
bitmapInfo |= kCGImageAlphaPremultipliedFirst;
}
// It calculates the bytes-per-row based on the bitsPerComponent and width arguments.
CGContextRef context = CGBitmapContextCreate(NULL,
imageSize.width,
imageSize.height,
CGImageGetBitsPerComponent(imageRef),
0,
colorSpace,
bitmapInfo);
CGColorSpaceRelease(colorSpace);
// If failed, return undecompressed image
if (!context) return image;