It… doesn’t matter if the images are aligned? I assumed the way it worked was to compare each pixel with the pixel at the same address in the other image.
If it doesn’t matter what order the images are in, I guess it shouldn’t matter if the two images are even perfectly aligned. If one were slightly stretched or squished relative to the other… that may not matter?
They should be perfectly aligned, but stretched or squished doesn’t matter, because it does not affect the information in the image. A squished or stretched number four is still a four. A number four that is missing it’s top is not a four. Because the method works with color distributions across the image, the precise location of the colors doesn’t matter, and so the order of the processed images doesn’t matter, but they should have the same content.