How to set the alpha of an UIImage in SWIFT programmatically?
I was able to set the alpha using the following code:
self.imageView.image = UIImageView(image: "image.png")
imageView.alpha = 0.5
Luckily I was able to help myself and would like to share with you my solution:
Swift 3
// UIImage+Alpha.swift
extension UIImage {
func alpha(_ value:CGFloat) -> UIImage {
UIGraphicsBeginImageContextWithOptions(size, false, scale)
draw(at: CGPoint.zero, blendMode: .normal, alpha: value)
let newImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return newImage!
}
}
The above new Swift extension I added to my project and then I changed the UIButton example as follows, to have an alpha transparent background image with a transparency of 50%.
let img = UIImage(named: "imageWithoutAlpha")!.alpha(0.5)
let myButton = UIButton()
myButton.setBackgroundImage(img, for: .normal)
The easiest way is to put your UIImage
inside a UIImageView
and set the alpha there.
let image = UIImage(named: "imageWithoutAlpha")
let imageView = UIImageView(image: image)
imageView.alpha = 0.5
myButton.setBackgroundImage(image, forState: UIControlState.Normal)
Swift 5, iOS 10+
If your app doesn't support operating systems prior to iOS 10 then you can take advantage of the more robust UIGraphicsImageRenderer
UIKit drawing API.
extension UIImage {
func withAlpha(_ a: CGFloat) -> UIImage {
return UIGraphicsImageRenderer(size: size, format: imageRendererFormat).image { (_) in
draw(in: CGRect(origin: .zero, size: size), blendMode: .normal, alpha: a)
}
}
}
Usage
let img = UIImage(named: "someImage")?.withAlpha(0.5)