iphone - slider 变化时模糊 UIImage

Question

我已经尝试过高斯模糊并检查了 stackoverflow 上的所有问题，但没有一个解决了我的崩溃问题。请帮助除了高斯模糊算法之外还有其他方法可以模糊图像。我的图像大小是 768x1024，循环迭代了 2*1024*768 次，这是不可行的。

CGContextRef NYXImageCreateARGBBitmapContext(const size_t width, const size_t height, const size_t bytesPerRow)
{
/// Use the generic RGB color space
/// We avoid the NULL check because CGColorSpaceRelease() NULL check the value anyway, and worst case scenario = fail to create context
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

/// Create the bitmap context, we want pre-multiplied ARGB, 8-bits per component
CGContextRef bmContext = CGBitmapContextCreate(NULL, width, height, 8/*Bits per component*/, bytesPerRow, colorSpace, kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedFirst);

CGColorSpaceRelease(colorSpace);

return bmContext;
}



 -(UIImage*)blurredImageUsingGaussFactor:(NSUInteger)gaussFactor andPixelRadius:(NSUInteger)pixelRadius
{
CGImageRef cgImage = self.CGImage;
const size_t originalWidth = CGImageGetWidth(cgImage);
const size_t originalHeight = CGImageGetHeight(cgImage);
const size_t bytesPerRow = originalWidth * 4;
CGContextRef context = NYXImageCreateARGBBitmapContext(originalWidth, originalHeight, bytesPerRow);
if (!context) 
    return nil;

unsigned char *srcData, *destData, *finalData;

size_t width = CGBitmapContextGetWidth(context);
size_t height = CGBitmapContextGetHeight(context);
size_t bpr = CGBitmapContextGetBytesPerRow(context);
size_t bpp = CGBitmapContextGetBitsPerPixel(context) / 8;
CGRect rect = {{0.0f, 0.0f}, {width, height}}; 

CGContextDrawImage(context, rect, cgImage); 

// Now we can get a pointer to the image data associated with the bitmap
// context.
srcData = (unsigned char*)CGBitmapContextGetData(context);
if (srcData != NULL)
{
    size_t dataSize = bpr * height;
    finalData = malloc(dataSize);
    destData = malloc(dataSize);
    memcpy(finalData, srcData, dataSize);
    memcpy(destData, srcData, dataSize);

    int sums[gaussFactor];
    size_t i, /*x, y,*/ k;
    int gauss_sum = 0;
    size_t radius = pixelRadius * 2 + 1;
    int *gauss_fact = malloc(radius * sizeof(int));

    for (i = 0; i < pixelRadius; i++)
    {
        gauss_fact[i] = 1 + (gaussFactor * i);
        gauss_fact[radius - (i + 1)] = 1 + (gaussFactor * i);
        gauss_sum += (gauss_fact[i] + gauss_fact[radius - (i + 1)]);
    }
    gauss_fact[(radius - 1) / 2] = 1 + (gaussFactor*pixelRadius);
    gauss_sum += gauss_fact[(radius - 1) / 2];

    unsigned char *p1, *p2, *p3;

    for (size_t y = 0; y < height; y++) 
    {
        for (size_t x = 0; x < width; x++) 
        {
            p1 = srcData + bpp * (y * width + x); 
            p2 = destData + bpp * (y * width + x);

            for (i = 0; i < gaussFactor; i++)
                sums[i] = 0;

            for (k = 0; k < radius ; k++)
            {
                if ((y - ((radius - 1) >> 1) + k) < height)
                    p1 = srcData + bpp * ((y - ((radius - 1) >> 1) + k) * width + x); 
                else
                    p1 = srcData + bpp * (y * width + x);

                for (i = 0; i < bpp; i++)
                    sums[i] += p1[i] * gauss_fact[k];

            }
            for (i = 0; i < bpp; i++)
                p2[i] = sums[i] / gauss_sum;
        }
    }
    for (size_t y = 0; y < height; y++) 
    {
        for (size_t x = 0; x < width; x++) 
        {
            p2 = destData + bpp * (y * width + x);
            p3 = finalData + bpp * (y * width + x);

            for (i = 0; i < gaussFactor; i++)
                sums[i] = 0;

            for(k = 0; k < radius ; k++)
            {
                if ((x - ((radius - 1) >> 1) + k) < width)
                    p1 = srcData + bpp * ( y * width + (x - ((radius - 1) >> 1) + k)); 
                else
                    p1 = srcData + bpp * (y * width + x);

                for (i = 0; i < bpp; i++)
                    sums[i] += p2[i] * gauss_fact[k];

            }
            for (i = 0; i < bpp; i++)
            {
                p3[i] = sums[i] / gauss_sum;
            }
        }
    }
}

size_t bitmapByteCount = bpr * height;

///////Here was the problem.. you had given srcData instead of destData.. Rest all 
//were perfect...
CGDataProviderRef dataProvider = CGDataProviderCreateWithData(NULL, destData, bitmapByteCount, NULL);

CGImageRef blurredImageRef = CGImageCreate(width, height, CGBitmapContextGetBitsPerComponent(context), CGBitmapContextGetBitsPerPixel(context), CGBitmapContextGetBytesPerRow(context), CGBitmapContextGetColorSpace(context), CGBitmapContextGetBitmapInfo(context), dataProvider, NULL, true, kCGRenderingIntentDefault);

CGDataProviderRelease(dataProvider);
CGContextRelease(context); 
if (destData)
    free(destData);
if (finalData)
    free(finalData);

UIImage* retUIImage = [UIImage imageWithCGImage:blurredImageRef];

CGImageRelease(blurredImageRef);

return retUIImage;
}

Answer 1

我对 UIImage 做了一个小的 StackBlur 扩展。 StackBlur 接近于 GaussianBlur，但速度更快。

查看:https://github.com/tomsoft1/StackBluriOS

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小记...那个自述文件上有一个错字，“normalized”是“normalize”