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://*.com/questions/12839729/correct-crop-of-cigaussianblur