Tag Archives: Image

original source : https://stackoverflow.com/questions/5084845/how-to-set-the-opacity-alpha-of-a-uiimage

#1 answer

https://stackoverflow.com/a/37955552/3151712

Based on Alexey Ishkov’s answer, but in Swift

I used an extension of the UIImage class.

Swift 2:

UIImage Extension:

extension UIImage {
    func imageWithAlpha(alpha: CGFloat) -> UIImage {
        UIGraphicsBeginImageContextWithOptions(size, false, scale)
        drawAtPoint(CGPointZero, blendMode: .Normal, alpha: alpha)
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return newImage
    }
}

To use:

let image = UIImage(named: "my_image")
let transparentImage = image.imageWithAlpha(0.5)

Swift 3 / Swift 4:

Note that this implementation returns an optional UIImage. This is because in Swift 3 UIGraphicsGetImageFromCurrentImageContext now returns an optional. This value could be nil if the context is nil or what not created with UIGraphicsBeginImageContext.

UIImage Extension:

extension UIImage {
    func image(alpha: CGFloat) -> UIImage? {
        UIGraphicsBeginImageContextWithOptions(size, false, scale)
        draw(at: .zero, blendMode: .normal, alpha: alpha)
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return newImage
    }
}

To use:

let image = UIImage(named: "my_image")
let transparentImage = image?.image(alpha: 0.5)