Stephen Wolf

Abstract:

This document discusses a method for correcting inaccurate color output by digital still and video imaging systems. The method uses a known reference image together with a least–squares algorithm to estimate the optimal color channel mixing matrix that must be applied to the output images in order to correct their color inaccuracies. The techniques presented in this document will provide users of digital photography and video equipment with an automated tool for correcting color output. For instance, digital photography users currently may try to correct color distortions in their images by trial and error using photo editing software. However, these correction procedures are time consuming and subjective and do not normally allow for arbitrary mixing of the color channels. The automated color correction matrix computation presented in this document allows each color component in the corrected image (e.g., red) to be calculated as a linear summation of a DC component and all the color components (e.g., red, green, and blue) in the uncorrected image. Methods to correct non-linearities in the color response of digital imaging systems are also discussed.

Keywords: digital; video; calibration; camera; channel; chart; color; colorspace; component; correction; matrix; non-linear; sRGB

Disclaimer: Certain commercial equipment, components, and software may be identified in this report to specify adequately the technical aspects of the reported results. In no case does such identification imply recommendation or endorsement by the National Telecommunications and Information Administration, nor does it imply that the equipment or software identified is necessarily the best available for the particular application or uses.

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