iOS 高斯模糊效果

CIContext *context = [CIContext contextWithOptions:nil];
CIImage *inputImage = [[CIImage alloc] initWithImage:[UIImage imageNamed:@"icon-user"]];
// create gaussian blur filter
CIFilter *filter = [CIFilter filterWithName:@"CIGaussianBlur"];
[filter setValue:inputImage forKey:kCIInputImageKey];
[filter setValue:[NSNumber numberWithFloat:3.0] forKey:@"inputRadius"];
// blur image
CIImage *result = [filter valueForKey:kCIOutputImageKey];
CGImageRef cgImage = [context createCGImage:result fromRect:[result extent]];
UIImage *image = [UIImage imageWithCGImage:cgImage];
CGImageRelease(cgImage);
mainImage.image = image;