如何在iPhone上高效快速地模糊图像？

Question

如果我有一个UIImage或CGContextRef或纯位图数据(直接访问解压的ARGB-8像素)，我最好的选择是尽可能快地模糊半径为10像素的图像？

Answer 1

要么使用堆栈模糊，要么使用框模糊，或者使用OpenGL纹理模糊(谷歌前两个，然后检查Apple dev示例中的后者)。

Answer 2

我已经为iOS实现了一个stackBlur算法，它与GaussianBlur很接近，但速度非常快：

https://github.com/tomsoft1/StackBluriOS

例如，请在此处查看：

Blur an UIImage on change of slider

Answer 3

https://github.com/rnystrom/RNBlurModalView

-(UIImage *)boxblurImageWithBlur:(CGFloat)blur bluringImage : (UIImage *) image
{

    int boxSize = (int)(blur * 40);
    boxSize = boxSize - (boxSize % 2) + 1;

    CGImageRef img = image.CGImage;
    enter code here
    vImage_Buffer inBuffer, outBuffer;

    vImage_Error error;

    void *pixelBuffer;


    //create vImage_Buffer with data from CGImageRef

    CGDataProviderRef inProvider = CGImageGetDataProvider(img);
    CFDataRef inBitmapData = CGDataProviderCopyData(inProvider);


    inBuffer.width = CGImageGetWidth(img);
    inBuffer.height = CGImageGetHeight(img);
    inBuffer.rowBytes = CGImageGetBytesPerRow(img);

    inBuffer.data = (void*)CFDataGetBytePtr(inBitmapData);

    //create vImage_Buffer for output

    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);

    // Create a third buffer for intermediate processing
    void *pixelBuffer2 = malloc(CGImageGetBytesPerRow(img) * CGImageGetHeight(img));
    vImage_Buffer outBuffer2;
    outBuffer2.data = pixelBuffer2;
    outBuffer2.width = CGImageGetWidth(img);
    outBuffer2.height = CGImageGetHeight(img);
    outBuffer2.rowBytes = CGImageGetBytesPerRow(img);

    //perform convolution
    error = vImageBoxConvolve_ARGB8888(&inBuffer, &outBuffer2, NULL, 0, 0, boxSize, boxSize, NULL, kvImageEdgeExtend);
    error = vImageBoxConvolve_ARGB8888(&outBuffer2, &inBuffer, NULL, 0, 0, boxSize, boxSize, NULL, kvImageEdgeExtend);
    error = vImageBoxConvolve_ARGB8888(&inBuffer, &outBuffer, NULL, 0, 0, boxSize, boxSize, NULL, kvImageEdgeExtend);

    if (error) {
        NSLog(@"error from convolution %ld", error);
    }

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef ctx = CGBitmapContextCreate(outBuffer.data,
                                            outBuffer.width,
                                            outBuffer.height,
                                            8,
                                            outBuffer.rowBytes,
                                            colorSpace,
                                            kCGImageAlphaNoneSkipLast);
    CGImageRef imageRef = CGBitmapContextCreateImage (ctx);
    UIImage *returnImage = [UIImage imageWithCGImage:imageRef];

    //clean up
    CGContextRelease(ctx);
    CGColorSpaceRelease(colorSpace);

    free(pixelBuffer);
    CFRelease(inBitmapData);

    CGImageRelease(imageRef);

    return returnImage;
}