Restoration of aged photos by color transplant

Starting from XVIII century, images have been used to testify the historical memories of the society. Among others, they are used for the representation of ancient documents, art objects, and similar. Even if the photographic technique has got several improvements since its origin, photos are still liable for several damages, both concerning the physical support and the colors and figures which are depicted in it: scratches or rips are examples of common physical injuries, while the fading or red (or yellow) toning of its colors are representative of “chemical” damages. In this paper, a novel method able to infer the original beauty of digital reproductions of aged photos is presented. It is based on the comparison between the degraded image and a not-degraded one, showing similar contents; that is, it is possible to transplant the colors coming from the not-degraded image in the degraded one. Similarly, the method can be also applied to digital reproductions of faded goods. The key point is a dualism between analytical mechanics and color theory; that is, the scatter plot diagrams of x and y normalized coordinates of the colors of both the images are computed, and each of them are accounted as a system of point masses, thus provided of an inertia ellipsoid and inertia axes. To perform the color correction of the degraded image, the inertia ellipsoid of it is moved up to overlap the not-degraded one, thus performing a transplant of colors.