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

Question

The setup is simple.

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

Answer 1

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:

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

Answer 2

You can add blur effect by UIBlurEffect and UIVisualEffectView:

@IBAction func blur(_ sender: Any) {

    let darkBlur = UIBlurEffect(style: UIBlurEffectStyle.dark) 
    let blurView = UIVisualEffectView(effect: darkBlur)
    blurView.frame = bg_imagview.bounds
    blurView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
    bg_imagview.addSubview(blurView)

}

Answer 3

There is actually a handy implementation right in CoreImage https://developer.apple.com/documentation/coreimage/ciimage/1645897-applyinggaussianblur

extension UIImage {

func blur(_ radius: Double) -> UIImage? {
    if let img = CIImage(image: self) {
        return UIImage(ciImage: img.applyingGaussianBlur(sigma: radius))
    }
    return nil
}

Answer 4

for those who ❤️ protocols

protocol Bluring {
    func addBlur(_ alpha: CGFloat)
}

extension Bluring where Self: UIView {
    func addBlur(_ alpha: CGFloat = 0.5) {
        // create effect
        let effect = UIBlurEffect(style: .dark)
        let effectView = UIVisualEffectView(effect: effect)

        // set boundry and alpha
        effectView.frame = self.bounds
        effectView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        effectView.alpha = alpha

        self.addSubview(effectView)
    }
}

// Conformance
extension UIView: Bluring {}

// use
someImageview.addBlur()

Answer 5

Here is how I got my expected result in SWIFT 3.1: Hope it will help.

func blurImage(image:UIImage) -> UIImage? {
        let context = CIContext(options: nil)
        let inputImage = CIImage(image: image)
        let originalOrientation = image.imageOrientation
        let originalScale = image.scale

        let filter = CIFilter(name: "CIGaussianBlur")
        filter?.setValue(inputImage, forKey: kCIInputImageKey)
        filter?.setValue(10.0, forKey: kCIInputRadiusKey) 
        let outputImage = filter?.outputImage

        var cgImage:CGImage?

        if let asd = outputImage
        {
            cgImage = context.createCGImage(asd, from: (inputImage?.extent)!)
        }

        if let cgImageA = cgImage
        {
            return UIImage(cgImage: cgImageA, scale: originalScale, orientation: originalOrientation)
        }

        return nil
    }

Answer 6

I made the blur in a NSObject class, so I can use this method in whole project easily.

class Helper: NSObject
{
    class func addBlurView(_ inView : UIView) -> UIVisualEffectView
    {
        let blurEffect = UIBlurEffect(style: UIBlurEffectStyle.dark)
        let blurEffectView = UIVisualEffectView(effect: blurEffect)

        //always fill the view
        blurEffectView.frame = inView.bounds
        blurEffectView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        blurEffectView.alpha = 0.5

        return blurEffectView
    }
}

In ViewController I made object of UIVisualEffectView. Then call the helper class method of to add blur.

import UIKit

class ViewController: UIViewController
{
   var blurEffectView : UIVisualEffectView!
    override func viewDidLoad() {
        super.viewDidLoad()

      blurEffectView = Helper.addBlurView((imgView)!)
      self.imgView.addSubview(blurEffectView)
}