1. A method of digitally transforming a skin image, the method comprising the following steps in sequence: (a) acquiring a digital image of the skin, to obtain the first image; (b) extracting an individual skin attribute from the digital image by linear digital filtering on all the color channels, to obtain a contrast map in all three channels of the individual attribute; and (c) transforming the first image by adding to the first image or subtracting from the first image a fraction of the contrast map, to obtain a second image with transformed individual skin attribute.