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Provide a way to fix libwebp’s bug during WebP progressive decoding for x86 architecture (macOS and iPhone simulator). It kept the previous decoded partial bitmap and will cause current image looks strange.

This commit is contained in:
DreamPiggy 2017-10-18 23:18:56 +08:00
parent e1a76d76bd
commit 23a174d859
1 changed files with 15 additions and 7 deletions
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22
SDWebImage/SDWebImageWebPCoder.m
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@ -190,11 +190,12 @@
return nil; return nil;
} }
int width; int width = 0;
int height; int height = 0;
uint8_t *rgba = WebPIDecGetRGB(_idec, NULL, (int *)&width, (int *)&height, NULL); int last_y = 0;
int stride = 0;
if (width + height > 0) { uint8_t *rgba = WebPIDecGetRGB(_idec, &last_y, &width, &height, &stride);
if (width + height > 0 && height >= last_y) {
// Construct a UIImage from the decoded RGBA value array // Construct a UIImage from the decoded RGBA value array
CGDataProviderRef provider = CGDataProviderRef provider =
CGDataProviderCreateWithData(NULL, rgba, 0, NULL); CGDataProviderCreateWithData(NULL, rgba, 0, NULL);
@ -203,7 +204,13 @@
CGBitmapInfo bitmapInfo = kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast; CGBitmapInfo bitmapInfo = kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast;
size_t components = 4; size_t components = 4;
CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault; CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
CGImageRef imageRef = CGImageCreate(width, height, 8, components * 8, components * width, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent); // Why to use last_y for image height is because of libwebp's bug (https://bugs.chromium.org/p/webp/issues/detail?id=362)
// It will not keep memory barrier safe on x86 architechure (macOS & iPhone simulator) but on ARM architecture (iPhone & iPad & tv & watch) it works great
// If different threads use WebPIDecGetRGB to grab rgba bitmap, it will contain the previous decoded bitmap data
// So this will cause our drawed image looks strange(above is the current part but below is the previous part)
// We only grab the last_y height and draw the last_y heigh instead of total height image
// Besides fix, this can enhance performance since we do not need to create extra bitmap
CGImageRef imageRef = CGImageCreate(width, last_y, 8, components * 8, components * width, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);
CGDataProviderRelease(provider); CGDataProviderRelease(provider);
@ -217,7 +224,8 @@
return nil; return nil;
} }
CGContextDrawImage(canvas, CGRectMake(0, 0, width, height), imageRef); // Only draw the last_y image height, keep remains transparent, in Core Graphics coordinate system
CGContextDrawImage(canvas, CGRectMake(0, height - last_y, width, last_y), imageRef);
CGImageRef newImageRef = CGBitmapContextCreateImage(canvas); CGImageRef newImageRef = CGBitmapContextCreateImage(canvas);
CGImageRelease(imageRef); CGImageRelease(imageRef);
if (!newImageRef) { if (!newImageRef) {