vImage Blur Example

blur.m

- (UIImage *)boxblurImage:(UIImage *)image boxSize:(int)boxSize
{
    CGImageRef originalImageRef = image.CGImage;
    CGColorSpaceRef originalColorSpace = CGColorSpaceRetain(CGImageGetColorSpace(originalImageRef));

    if (_pixelBuffer == NULL) {
        _pixelBuffer = malloc(CGImageGetBytesPerRow(originalImageRef) * CGImageGetHeight(originalImageRef));
    }

    vImage_CGImageFormat inputImageFormat =
    {
        .bitsPerComponent = (uint32_t) CGImageGetBitsPerComponent(originalImageRef),
        .bitsPerPixel = (uint32_t) CGImageGetBitsPerComponent(originalImageRef) * (uint32_t)(CGColorSpaceGetNumberOfComponents(originalColorSpace) + (kCGImageAlphaNone != CGImageGetAlphaInfo(originalImageRef))),
        .colorSpace = originalColorSpace,
        .bitmapInfo = CGImageGetBitmapInfo(originalImageRef),
        .version = 0,
        .decode = NULL,
        .renderingIntent = kCGRenderingIntentDefault
    };
    vImage_Buffer inputImageBuffer;
    vImageBuffer_InitWithCGImage(&inputImageBuffer, &inputImageFormat, NULL, originalImageRef, kvImageNoFlags);

    vImage_Buffer outputImageBuffer = {
        .data = _pixelBuffer,
        .width = CGImageGetWidth(originalImageRef),
        .height = CGImageGetHeight(originalImageRef),
        .rowBytes = CGImageGetBytesPerRow(originalImageRef)
    };
    
    vImage_Error error;
    error = vImageBoxConvolve_ARGB8888(&inputImageBuffer,
                                       &outputImageBuffer,
                                       NULL,
                                       0,
                                       0,
                                       boxSize,
                                       boxSize,
                                       NULL,
                                       kvImageEdgeExtend);
    if (error) {
        NSLog(@"vImage error %zd", error);
    }

    vImage_CGImageFormat outFormat =
    {
        .bitsPerComponent = (uint32_t) CGImageGetBitsPerComponent(originalImageRef),
        .bitsPerPixel = (uint32_t) CGImageGetBitsPerComponent(originalImageRef) * (uint32_t)(CGColorSpaceGetNumberOfComponents(originalColorSpace) + (kCGImageAlphaNone != CGImageGetAlphaInfo(originalImageRef))),
        .colorSpace = originalColorSpace,
        .bitmapInfo = CGImageGetBitmapInfo(originalImageRef),
        .version = 0,
        .decode = NULL,
        .renderingIntent = kCGRenderingIntentDefault
    };
    CGImageRef modifiedImageRef = vImageCreateCGImageFromBuffer(&outputImageBuffer,
                                                                &outFormat,
                                                                NULL,
                                                                NULL,
                                                                kvImageNoFlags,
                                                                &error);
    CGColorSpaceRelease(originalColorSpace);

    UIImage *returnImage = [UIImage imageWithCGImage:modifiedImageRef];
    CGImageRelease(modifiedImageRef);
    free(inputImageBuffer.data);

    return returnImage;
}