Img.x and img.y is changed. Its result get new attribute in query feature because new img.x and img.y set new position of point on the map. However, imgext and imgxy does not change. imgext and imgxy is calculated in order to get img.x and img.y.
relation of parameter of img.x, img.y and img.ext. imgxy in URL is four parameter have relation and important for show location in map to user.