adding image to called function from another class in swift - swift

Question

I have started working with swift recently. I have a function to resize the image in one swift file and I wanted to call it in another swift file. Here is the function which was added in class UIImage:
public extension UIImage{
class func scalePreservingAspectRatio(targetSize: CGSize) -> UIImage {
let uimageview = UIImage()
let widthRatio = targetSize.width / uimageview.size.width
let heightRatio = targetSize.height / uimageview.size.height
let scaleFactor = min(widthRatio, heightRatio)
let scaledImageSize = CGSize(
width: uimageview.size.width * scaleFactor,
height: uimageview.size.height * scaleFactor
)
let renderer = UIGraphicsImageRenderer(
size: scaledImageSize
)
let scaledImage = renderer.image { _ in
uimageview.draw(in: CGRect(
origin: .zero,
size: scaledImageSize
))
}
return scaledImage
}
}
so when I want to call this function in another file to resize "myimage", I think I should write like this:
let image = UIImage(named: "myimage")
let targetSize = CGSize(width: 100, height: 100)
let scaledImage = image.UIImage.scalePreservingAspectRatio(targetSize: targetSize)
but by adding 'image' before UIImage.scalePreservingAspectRatio(), it does not recognize the function and it shows an error: Value of type 'UIImage?' has no member 'UIImage'. So I don't know how I can use my image for this function in another file.

Answer 1

If you want to call it on UIImage, it needs to be put into an extension:
extension UIImage {
func scalePreservingAspectRatio(targetSize: CGSize) -> UIImage {
...
}
}
You also probably want it to be able to access the image that you call it on, so remove class from the function declaration. Then you can call it like:
image.scalePreservingAspectRatio(targetSize: size)
Then update the code to use self instead of creating a new source image:
func scalePreservingAspectRatio(targetSize: CGSize) -> UIImage {
let widthRatio = targetSize.width / size.width
let heightRatio = targetSize.height / size.height
let scaleFactor = min(widthRatio, heightRatio)
let scaledImageSize = CGSize(
width: size.width * scaleFactor,
height: size.height * scaleFactor
)
let renderer = UIGraphicsImageRenderer(
size: scaledImageSize
)
let scaledImage = renderer.image { _ in
self.draw(in: CGRect(
origin: .zero,
size: scaledImageSize
))
}
return scaledImage
}