This snippet shows adding a gaussian blur using the Quartz Core Framework

Gaussian Blur

CIImage *headerImage = [[CIImage alloc] initWithImage: self.headerImageView.image];
    CIFilter *blurFilter = [CIFilter filterWithName: @"CIGaussianBlur"
                                      keysAndValues: kCIInputImageKey, headerImage, @"inputRadius", @(3.0), nil];
    CIImage *outputImage = [blurFilter outputImage];
    self.context = [CIContext contextWithOptions: nil];
    CGImageRef outImage = [self.context createCGImage:outputImage
                                             fromRect: [outputImage extent]];
    self.headerImageView.image = [UIImage imageWithCGImage: outImage];