Apply CIGaussianBlur only to a small part of an image

Question

I need to apply a CIGaussianBlur filter only on a small part of an image like this:

Is there any way to do this? For example when I apply the filter perhaps I think that I have to specify the dimension of the filter (someone like CGRectMake).

var imageToBlur = CIImage(image: coro.logo)
var blurfilter = CIFilter(name: "CIGaussianBlur")
blurfilter.setValue(imageToBlur, forKey: "inputImage")
blurfilter.setValue(2, forKey: "inputRadius")
var resultImage = blurfilter.valueForKey("outputImage") as! CIImage
var blurredImage = UIImage(CIImage: resultImage)
self.immagineCoro.image = blurredImage

Answer 1

Try to use this

func blurImage(image:UIImage, forRect rect: CGRect) -> UIImage?
    {
        let context = CIContext(options: nil)
        let inputImage = CIImage(CGImage: image.CGImage!)


        let filter = CIFilter(name: "CIGaussianBlur")
        filter?.setValue(inputImage, forKey: kCIInputImageKey)
        filter?.setValue((70.0), forKey: kCIInputRadiusKey)
        let outputImage = filter?.outputImage

        var cgImage:CGImageRef?

        if let asd = outputImage
        {
            cgImage = context.createCGImage(asd, fromRect: rect)
        }

        if let cgImageA = cgImage
        {
            return UIImage(CGImage: cgImageA)
        }

        return nil
    }