iOS 高斯模糊(高性能,不会变蓝)

出自这里https://www.zhihu.com/question/21260575/answer/18401841

+ (UIImage *)accelerateBlurWithImage:(UIImage *)image
{
    NSInteger boxSize = (NSInteger)(10 * 5);
    boxSize = boxSize - (boxSize % 2) + 1;
    
    CGImageRef img = image.CGImage;
    
    vImage_Buffer inBuffer, outBuffer, rgbOutBuffer;
    vImage_Error error;
    
    void *pixelBuffer, *convertBuffer;
    
    CGDataProviderRef inProvider = CGImageGetDataProvider(img);
    CFDataRef inBitmapData = CGDataProviderCopyData(inProvider);
    
    convertBuffer = malloc( CGImageGetBytesPerRow(img) * CGImageGetHeight(img) );
    rgbOutBuffer.width = CGImageGetWidth(img);
    rgbOutBuffer.height = CGImageGetHeight(img);
    rgbOutBuffer.rowBytes = CGImageGetBytesPerRow(img);
    rgbOutBuffer.data = convertBuffer;
    
    inBuffer.width = CGImageGetWidth(img);
    inBuffer.height = CGImageGetHeight(img);
    inBuffer.rowBytes = CGImageGetBytesPerRow(img);
    inBuffer.data = (void *)CFDataGetBytePtr(inBitmapData);
    
    pixelBuffer = malloc( CGImageGetBytesPerRow(img) * CGImageGetHeight(img) );
    
    if (pixelBuffer == NULL) {
        NSLog(@"No pixelbuffer");
    }
    
    outBuffer.data = pixelBuffer;
    outBuffer.width = CGImageGetWidth(img);
    outBuffer.height = CGImageGetHeight(img);
    outBuffer.rowBytes = CGImageGetBytesPerRow(img);
    
    void *rgbConvertBuffer = malloc( CGImageGetBytesPerRow(img) * CGImageGetHeight(img) );
    vImage_Buffer outRGBBuffer;
    outRGBBuffer.width = CGImageGetWidth(img);
    outRGBBuffer.height = CGImageGetHeight(img);
    outRGBBuffer.rowBytes = 3;
    outRGBBuffer.data = rgbConvertBuffer;
    
    error = vImageBoxConvolve_ARGB8888(&inBuffer, &outBuffer, NULL, 0, 0, boxSize, boxSize, NULL, kvImageEdgeExtend);
    
    if (error) {
        NSLog(@"error from convolution %ld", error);
    }
    const uint8_t mask[] = {2, 1, 0, 3};
    
    vImagePermuteChannels_ARGB8888(&outBuffer, &rgbOutBuffer, mask, kvImageNoFlags);
    
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef ctx = CGBitmapContextCreate(rgbOutBuffer.data,
                                             rgbOutBuffer.width,
                                             rgbOutBuffer.height,
                                             8,
                                             rgbOutBuffer.rowBytes,
                                             colorSpace,
                                             kCGImageAlphaNoneSkipLast);
    CGImageRef imageRef = CGBitmapContextCreateImage(ctx);
    UIImage *returnImage = [UIImage imageWithCGImage:imageRef];
    
    //clean up
    CGContextRelease(ctx);
    
    free(pixelBuffer);
    free(convertBuffer);
    free(rgbConvertBuffer);
    CFRelease(inBitmapData);
    
    CGColorSpaceRelease(colorSpace);
    CGImageRelease(imageRef);
    
    return returnImage;
}