Patent ID: 7443552

Claim:
An automatic process of color restoration of a silver image whose color is altered with regard to an original color of said silver image the color alteration not occurring evenly, spatially in the plane of the image, and according to a direction parallel to one main axis of the image; said process comprises the steps of: a) digitizing the altered silver image by using a measuring scale of optical densities to create a digital image; b) filtering all pixels of the digital image; c) dividing the digital image into pixel strips arranged perpendicular to a direction of a main axis of the image according to which the color alteration occurs, a joining of all the pixels of each strip representing all the pixels of the digital image; d) calculating for each pixel strip, and for each of color channels forming the image, a distribution of optical densities of the pixels forming said strip; e) calculating for each of said distributions of said step d), a top crude reference value of optical density, and a bottom crude reference value of optical density; f) calculating from all the top and bottom crude reference values of said step e), respectively corresponding top filtered reference values of optical density and bottom filtered reference values of optical density; g) determining from the top and bottom filtered reference values of optical density of said step f), respectively top reference curves of optical density and bottom reference curves of optical density, said reference curves being representative of a color degradation profile of the image; h) determining for each of the color channels forming the image, and from a maximum value of optical density of the top reference curve of optical density, a pixel strip of least degradation; i) applying to each pixel strip of the digital image other than the pixel strip of least degradation, and to each of the color channels forming the image, a linear transformation enabling a transformation of the optical density filtered values placed on the top reference curve and on the bottom reference curve of optical density of said each pixel strip, respectively into top and bottom values of optical density of the pixel strip of least degradation.