Swift：UIImage的大小是原来的两倍

Question

When I draw a border around a UIImage with

    let opaque = false
    let scale: CGFloat = 0
    UIGraphicsBeginImageContextWithOptions(CGSize.init(width: ((self.imageView?.image?.size.width)!+512), height: (self.imageView?.image?.size.height)!+512), opaque, scale)
    let context = UIGraphicsGetCurrentContext()

    context?.setFillColor(UIColor.yellow.cgColor)
    context?.fill(CGRect.init(x: 0, y: 0, width: (context?.width)!, height: (context?.width)!))

    self.imageView?.image?.draw(at: CGPoint.init(x: 256, y: 256))

    let image = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

and print out its size, it is totally correct, as I set it: width and height each + 256.

However, when I save the image to library, it has twice its width and twice its height. I have no idea why. Also (and this is the part that annoys me the most), when I want to draw something on the image, also it seem to have twice the sizes...

Answer 1

Thanks, Maddy, for bringing me on the right track!

The solution is: The ScaleFactor has to be 1:

let scale: CGFloat = 1