Blur UIImage to achieve effect like passcode blur of the wallpaper with swift

Question

I want to achieve the effect that passcode view have (the wallpaper picture is blurred and darker)

This give me a black screen

func blurWithCoreImage(){

    var inputImage = CIImage(image: UIImage(named: "wallpaper"));

    // Apply gaussian blur filter with radius of 30
    var gaussianBlurFilter = CIFilter(name: "CIGaussianBlur");
    gaussianBlurFilter.setValue(inputImage, forKey: "inputImage")
    gaussianBlurFilter.setValue(30, forKey: "inputRadius")

    var context  =  CIContext(options:nil)
    var cgImage = context.createCGImage(gaussianBlurFilter.outputImage, fromRect: inputImage.extent())

    // Set up output context.
    UIGraphicsBeginImageContext(self.view.frame.size);
    var outputContext = UIGraphicsGetCurrentContext();

    // Invert image coordinates
    CGContextScaleCTM(outputContext, 1.0, -1.0);
    CGContextTranslateCTM(outputContext, 0, -self.view.frame.size.height);

    // Draw base image.
    CGContextDrawImage(outputContext, self.view.frame, cgImage);

    // Apply white tint
    CGContextSaveGState(outputContext);
    //  CGContextSetFillColorWithColor(outputContext, UIColor.blackColor().CGColor!);

    CGContextFillRect(outputContext, self.view.frame);
    CGContextRestoreGState(outputContext);

    // Output image is ready.
    var outputImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    backgroundImg.image =  outputImage;
}

This function make the image to blur but allso shrink the image and is too far from effect in passcode view

func blurWithCoreImage2(){
    var ciimage = CIImage(image: UIImage(named: "passcode"))

    var filter = CIFilter(name:"CIGaussianBlur")

    filter.setDefaults()

    filter.setValue(ciimage, forKey: kCIInputImageKey)

    filter.setValue(1, forKey: kCIInputRadiusKey)

    var outputImage = filter.outputImage;

    var finalImage = UIImage(CIImage: outputImage);
    backgroundImg.image =  finalImage;
    UIGraphicsEndImageContext();

}

Answer 1

As you only need to support iOS 8 and above you can use the new UIVisualEffectView, which is the new built-in way of adding blur.

It's very easy to use, something like the following:

let blurEffect = UIBlurEffect(style: UIBlurEffectStyle.Dark)
let blurView = UIVisualEffectView(effect: blurEffect)
blurView.frame = myFrame
self.view.addSubview(blurView)

You can see that you can specifiy a UIBlurEffectStyle, which will allow you to make it darker as well.