CIImage doubles size of resized image - ios

Question

I have the following code in a playground:
import UIKit
var str = "Hello, playground"
func rescaledImage(_ image: UIImage, with newSize: CGSize) -> UIImage {
let renderer = UIGraphicsImageRenderer(size: newSize)
let rescaled = renderer.image { _ in
image.draw(in: CGRect.init(origin: CGPoint.zero, size: newSize))
}
return rescaled
}
let original = UIImage(named: "burn.jpg")!
let resized = rescaledImage(original, with: CGSize(width: 200, height: 200))
let ciImage = CIImage(image: resized)
burn.jpg is a 5000 pixel by 5000 pixel black and white jpg.
The resized image is properly 200 pixels by 200 pixels. The ciImage however, is 400 pixels by 400 pixels. In fact, no matter what I resize it to, the ciImage is always doubled.
However, if I just make ciImage out of the original:
let ciImage = CIImage(image: original)
the ciImage will be 5000 by 5000 pixels, instead of being doubled.
So what is causing this doubling? Something in the format of the resized image must be causing this, but I cannot seem to isolate it.
Note that this doubling also happens if I use UIGraphicsBeginImageContextWithOptions instead.
func imageWithImage(image:UIImage, scaledToSize newSize:CGSize) -> UIImage {
UIGraphicsBeginImageContextWithOptions(newSize, false, 0.0);
image.draw(in: CGRect(origin: CGPoint.zero, size: CGSize(width: newSize.width, height: newSize.height)))
let newImage:UIImage = UIGraphicsGetImageFromCurrentImageContext()!
UIGraphicsEndImageContext()
return newImage
}

Answer 1

If you check the scale of your images, you'll notice that the original.scale is probably 1, while the resized.scale is probably 2.
You can set the scale of the renderer using UIGraphicsImageRendererFormat, and see if that helps.
func rescaledImage(_ image: UIImage, with newSize: CGSize) -> UIImage {
let format = UIGraphicsImageRendererFormat()
format.scale = 1
let renderer = UIGraphicsImageRenderer(size: newSize, format: format)
let rescaled = renderer.image { _ in
image.draw(in: CGRect.init(origin: CGPoint.zero, size: newSize))
}
return rescaled
}