Exact Reproduction of Colored Images
The problem of producing a colored image from a colored original is analyzed. Conditions are determined for the production of an image, in which the colors cannot be distinguished from those in the original by a human observer. If the final image is produced by superposition of controlled amounts of colored lights, only a simple linear transform need be applied to the outputs of the image sensors to produce the control inputs required for the image generators. In systems which depend instead on control of the concentration or fractional area covered by colored dyes, a more difficult computation is called for. This calculation may for practical purposes be expressed in table look-up form. The conditions for exact reproduction of colored images should prove useful in the design and analysis of image processing systems whose final output is intended for human viewing. Judging by the design of many existing systems, these rules are not generally known or adhered to. Modern computational techniques make it practical to tackle this problem now. Adherence to design constraints developed here is of particular important where colors are to be judged when the original is not directly accessible to the observer as, for example, when it is on another planet.