更改滑块时使UIImage模糊

Question

我尝试过高斯模糊，并检查了stackoverflow上的所有问题，但没有一个解决我的崩溃问题。请帮忙，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GaussianBlur，但速度要快得多。

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

---

小音符。。。ReadMe上有一个拼写错误，"normalized"表示"normalize"

Answer 2

不确定如何模糊图像。如果您想要blur an UIImageView or any view，这可能会有所帮助。

   UIView *myView = self.theImageView;
    CALayer *layer = [myView layer];
    [layer setRasterizationScale:0.25];
    [layer setShouldRasterize:YES];

您可以通过将光栅化比例设置回1来撤消它。

[layer setRasterizationScale:1.0];

更新：

下面的苹果示例代码包含模糊/锐化效果。（使用Open GL）看看它是否有帮助，http://developer.apple.com/library/ios/#samplecode/GLImageProcessing/Introduction/Intro.html

Answer 3

您可能想要的是Box Blur算法。它的速度大约是高斯模糊的10倍，并且产生了很好的结果。我的代码在安卓系统上运行，只是还没有移植到iOS。这是消息来源。

移植到iOS应该只需要大约10分钟。函数将按原样工作，您只需要访问图像字节（就像您在上面的源代码中所做的那样）并将它们提供给函数。