How to compare image on pixel data? And How to compare color of two images using colorAbsoluteDifference CIFilter? To compare image on pixel data you need CGImage object of UIImage. Sometime when you create computed image through CIFilter and directly create UIImage from CIImage. It does not have CGImage data, so we need to covert CIImage to CGImage first and then get pixel data to compare Get pixel data of images and compare through == operator.