Swift 5 Resize image to pixel size before upload

Question

I have a web service that I send images from iOS to. Before sending the images, I want to reduce the file size to a max. width of 1024 px to save bandwidth

I have tried

let size = CGSize(width: 1024, height: 768)
let renderer = UIGraphicsImageRenderer(size: size)


//https://nshipster.com/image-resizing/

let smallImage = renderer.image { (context) in
uiImage.draw(in: CGRect(origin: .zero, size: size))
}

but that always produces different output pixel sizes. What do I have to do to make sure that the output image does not exceed a width of 1024 px?

Answer 1

This one seems to work fine, you need to consider the scaling aspect of the different screens:

let scaleFactor = UIScreen.main.scale
let scale = CGAffineTransform(scaleX: scaleFactor, y: scaleFactor)

let width = 1024 / scale.a
let height = 768 / scale.d

let size = CGSize(width: width, height: height)
let renderer = UIGraphicsImageRenderer(size: size)

let smallImage = renderer.image { (context) in
    uiImage.draw(in: CGRect(origin: .zero, size: size))
}