Proper lightness correction is unavailable if a determination is unsuccessfully made whether or not an image to be retouched is a backlight image. A distribution ratio of luminance components is obtained from an image whose type is to be determined. The similarity is determined between the distribution ratio and a distribution ratio in the image of a specific type. When the similarity is acknowledged, it is determined that the image under inspection corresponds to the specific type. When a distribution ratio for backlight image is obtained in advance as the distribution ratio for the specific type of image, the above-mentioned determination process makes it possible to accurately determine whether or not the image under inspection is a backlight image.