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Fix the sd_colorAtPoint return wrong value on pre-multiplied CGImage 

Should always un-multiplied the color to match CGColor/UIColor documentation
This commit is contained in:
DreamPiggy 2023-11-15 17:46:53 +08:00
parent 213be11357
commit 9efacfed97
2 changed files with 62 additions and 8 deletions
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2
SDWebImage/Core/UIImage+Transform.h
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@ -107,6 +107,7 @@ typedef NS_OPTIONS(NSUInteger, SDRectCorner) {
/**
Return the pixel color at specify position. The point is from the top-left to the bottom-right and 0-based. The returned the color is always be RGBA format. The image must be CG-based.
@note The point's x/y will be converted into integer.
@note The point's x/y should not be smaller than 0, or greater than or equal to width/height.
@note The overhead of object creation means this method is best suited for infrequent color sampling. For heavy image processing, grab the raw bitmap data and process yourself.
@ -117,6 +118,7 @@ typedef NS_OPTIONS(NSUInteger, SDRectCorner) {
/**
Return the pixel color array with specify rectangle. The rect is from the top-left to the bottom-right and 0-based. The returned the color is always be RGBA format. The image must be CG-based.
@note The rect's origin and size will be converted into integer.
@note The rect's width/height should not be smaller than or equal to 0. The minX/minY should not be smaller than 0. The maxX/maxY should not be greater than width/height. Attention this limit is different from `sd_colorAtPoint:` (point: (0, 0) like rect: (0, 0, 1, 1))
@note The overhead of object creation means this method is best suited for infrequent color sampling. For heavy image processing, grab the raw bitmap data and process yourself.

68
SDWebImage/Core/UIImage+Transform.m
View File

@ -169,7 +169,32 @@ static inline UIColor * SDGetColorFromRGBA(Pixel_8888 pixel, CGBitmapInfo bitmap
default: break;
}
switch (alphaInfo) {
case kCGImageAlphaPremultipliedFirst:
case kCGImageAlphaPremultipliedFirst: {
if (byteOrderNormal) {
// ARGB8888-premultiplied
a = pixel[0] / 255.0;
r = pixel[1] / 255.0;
g = pixel[2] / 255.0;
b = pixel[3] / 255.0;
if (a > 0) {
r /= a;
g /= a;
b /= a;
}
} else {
// BGRA8888-premultiplied
b = pixel[0] / 255.0;
g = pixel[1] / 255.0;
r = pixel[2] / 255.0;
a = pixel[3] / 255.0;
if (a > 0) {
r /= a;
g /= a;
b /= a;
}
}
break;
}
case kCGImageAlphaFirst: {
if (byteOrderNormal) {
// ARGB8888
@ -186,7 +211,32 @@ static inline UIColor * SDGetColorFromRGBA(Pixel_8888 pixel, CGBitmapInfo bitmap
}
}
break;
case kCGImageAlphaPremultipliedLast:
case kCGImageAlphaPremultipliedLast: {
if (byteOrderNormal) {
// RGBA8888-premultiplied
r = pixel[0] / 255.0;
g = pixel[1] / 255.0;
b = pixel[2] / 255.0;
a = pixel[3] / 255.0;
if (a > 0) {
r /= a;
g /= a;
b /= a;
}
} else {
// ABGR8888-premultiplied
a = pixel[0] / 255.0;
b = pixel[1] / 255.0;
g = pixel[2] / 255.0;
r = pixel[3] / 255.0;
if (a > 0) {
r /= a;
g /= a;
b /= a;
}
}
break;
}
case kCGImageAlphaLast: {
if (byteOrderNormal) {
// RGBA8888
@ -546,9 +596,11 @@ static inline CGImageRef _Nullable SDCreateCGImageFromCIImage(CIImage * _Nonnull
}
// Check point
CGFloat width = CGImageGetWidth(imageRef);
CGFloat height = CGImageGetHeight(imageRef);
if (point.x < 0 || point.y < 0 || point.x >= width || point.y >= height) {
size_t width = CGImageGetWidth(imageRef);
size_t height = CGImageGetHeight(imageRef);
size_t x = point.x;
size_t y = point.y;
if (x < 0 || y < 0 || x >= width || y >= height) {
CGImageRelease(imageRef);
return nil;
}
@ -570,7 +622,7 @@ static inline CGImageRef _Nullable SDCreateCGImageFromCIImage(CIImage * _Nonnull
size_t components = CGImageGetBitsPerPixel(imageRef) / CGImageGetBitsPerComponent(imageRef);
CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
CFRange range = CFRangeMake(bytesPerRow * point.y + components * point.x, components);
CFRange range = CFRangeMake(bytesPerRow * y + components * x, components);
if (CFDataGetLength(data) < range.location + range.length) {
CFRelease(data);
CGImageRelease(imageRef);
@ -620,8 +672,8 @@ static inline CGImageRef _Nullable SDCreateCGImageFromCIImage(CIImage * _Nonnull
}
// Check rect
CGFloat width = CGImageGetWidth(imageRef);
CGFloat height = CGImageGetHeight(imageRef);
size_t width = CGImageGetWidth(imageRef);
size_t height = CGImageGetHeight(imageRef);
if (CGRectGetWidth(rect) <= 0 || CGRectGetHeight(rect) <= 0 || CGRectGetMinX(rect) < 0 || CGRectGetMinY(rect) < 0 || CGRectGetMaxX(rect) > width || CGRectGetMaxY(rect) > height) {
CGImageRelease(imageRef);
return nil;