Comparing UIImage

Question

How can I compare an image to another one?

Thanks!

Answer 1

Update

Based on Skycamelfalling's comment, I verified that my unit tests still pass when using UIImage's pngData() method, instead of drawing with an image context. Much simpler!

For historic interest: Here is a Swift 4 variant of hpique's answer. It's working for me in my unit tests, when I need to test two UIImages for "sameness".

fileprivate extension UIImage {
    func makeNormalizedData() -> Data? {
        defer { UIGraphicsEndImageContext() }
        let pixelSize = CGSize(width: size.width * scale, height: size.height * scale)
        UIGraphicsBeginImageContext(pixelSize)
        draw(in: CGRect(origin: CGPoint.zero, size: pixelSize))
        guard let drawnImage = UIGraphicsGetImageFromCurrentImageContext() else { return nil }
        return UIImagePNGRepresentation(drawnImage)
    }
}