iOS 图像处理 － 模糊图像

解决问题：将图像模糊

前提：添加 CoreGraphics.framework

源码：

- (UIImage*) blur:(UIImage*)theImage
{
    // create our blurred image
    CIContext *context = [CIContext contextWithOptions:nil];
    CIImage *inputImage = [CIImage imageWithCGImage:theImage.CGImage];

    // setting up Gaussian Blur (could use one of many filters offered by Core Image)
    CIFilter *blurFilter = [CIFilter filterWithName:@"CIGaussianBlur"];
    [blurFilter setValue:inputImage forKey:kCIInputImageKey];
    [blurFilter setValue:[NSNumber numberWithFloat:10.0f] forKey:@"inputRadius"];
    CIImage *result = [blurFilter valueForKey:kCIOutputImageKey];

    // CIGaussianBlur has a tendency to shrink the image a little,
    // this ensures it matches up exactly to the bounds of our original image
    CGImageRef cgImage = [context createCGImage:result fromRect:[inputImage extent]];

    UIImage *returnImage = [UIImage imageWithCGImage:cgImage];
    //create a UIImage for this function to "return" so that ARC can manage the memory of the blur...
    //ARC can't manage CGImageRefs so we need to release it before this function "returns" and ends.
    CGImageRelease(cgImage);//release CGImageRef because ARC doesn't manage this on its own.

    return returnImage;
}

出现问题：因为在模糊的时候，边缘会变成半透明的状态，所以理想状况是可以对原图像进行适当放大，选择使用CIAffineClamp在模糊之前对图像进行处理。

源码：

- (UIImage*) blur:(UIImage*)theImage
{
    // create our blurred image
    CIContext *context = [CIContext contextWithOptions:nil];
    CIImage *inputImage = [CIImage imageWithCGImage:theImage.CGImage];

    CIFilter *affineClampFilter = [CIFilter filterWithName:@"CIAffineClamp"];
    CGAffineTransform xform = CGAffineTransformMakeScale(1.0, 1.0);
    [affineClampFilter setValue:inputImage forKey:kCIInputImageKey];
    [affineClampFilter setValue:[NSValue valueWithBytes:&xform
                                               objCType:@encode(CGAffineTransform)]
                                                 forKey:@"inputTransform"];

    CIImage *extendedImage = [affineClampFilter valueForKey:kCIOutputImageKey];

    // setting up Gaussian Blur (could use one of many filters offered by Core Image)
    CIFilter *blurFilter = [CIFilter filterWithName:@"CIGaussianBlur"];
    [blurFilter setValue:extendedImage forKey:kCIInputImageKey];
    [blurFilter setValue:[NSNumber numberWithFloat:10.0f] forKey:@"inputRadius"];
    CIImage *result = [blurFilter valueForKey:kCIOutputImageKey];

    // CIGaussianBlur has a tendency to shrink the image a little,
    // this ensures it matches up exactly to the bounds of our original image
    CGImageRef cgImage = [context createCGImage:result fromRect:[inputImage extent]];

    UIImage *returnImage = [UIImage imageWithCGImage:cgImage];
    //create a UIImage for this function to "return" so that ARC can manage the memory of the blur...
    //ARC can't manage CGImageRefs so we need to release it before this function "returns" and ends.
    CGImageRelease(cgImage);//release CGImageRef because ARC doesn't manage this on its own.

    return returnImage;
}

参考：（网上资源，部分链接已丢失）

http://stackoverflow.com/questions/12839729/correct-crop-of-cigaussianblur

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