How to blur an existing image in a UIImageView with Swift?

Mark Moeykens picture Mark Moeykens · Dec 15, 2016 · Viewed 26.9k times · Source

The setup is simple.

  • A ViewController with UIImageView that has an image assigned.
  • A UIButton that when clicked blurs the image in the UIImageView.

Storyboard

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var bg: UIImageView!

    @IBAction func blur(_ sender: Any) {
        let inputImage = CIImage(cgImage: (bg.image?.cgImage)!)

        let filter = CIFilter(name: "CIGaussianBlur")
        filter?.setValue(inputImage, forKey: "inputImage")
        filter?.setValue(10, forKey: "inputRadius")
        let blurred = filter?.outputImage
        bg.image = UIImage(ciImage: blurred!)
    }
}

When the button is clicked the screen just turns white. Can't figure out what I'm doing wrong. Anyone know what I'm doing wrong?

Answer

Joe picture Joe · Dec 15, 2016

You could simply use UIVisualEffect to achieve blur effect. As you trying to achieve a blur effect using CoreImage.Try below code after import CoreImage to your class.

var context = CIContext(options: nil)

func blurEffect() {

    let currentFilter = CIFilter(name: "CIGaussianBlur") 
    let beginImage = CIImage(image: bg.image!)
    currentFilter!.setValue(beginImage, forKey: kCIInputImageKey)
    currentFilter!.setValue(10, forKey: kCIInputRadiusKey)

    let cropFilter = CIFilter(name: "CICrop")
    cropFilter!.setValue(currentFilter!.outputImage, forKey: kCIInputImageKey)
    cropFilter!.setValue(CIVector(cgRect: beginImage!.extent), forKey: "inputRectangle")

    let output = cropFilter!.outputImage 
    let cgimg = context.createCGImage(output!, from: output!.extent)
    let processedImage = UIImage(cgImage: cgimg!)
    bg.image = processedImage
}

Output:

enter image description here

Note: I recommend you to test the code in real device as Simulator performance is too slow on coreImage.