DETERMINING VISUALLY NOTICEABLE DIFFERENCES BETWEEN TWO IMAGES

The present invention relates to a method and apparatus for determining visually noticeable differences between two input images. A first contrast image is generated from the first input image and a second contrast image is generated from the second input image. A contrast difference image is then formed from the two contrast images. A mean absolute difference is calculated between blocks of pixels of the first and second input image. Pixels in the contrast difference image which exceed a first threshold produce a first threshold signal and if the mean absolute difference exceeds a second threshold so a second threshold signal is produced. A detection signal is produced from the threshold signals.