In-gamut image reproduction using spatial comparisons

Abstract

A process and apparatus is described to improve color digital imaging reproduction quality by quickly, accurately and robustly mapping the gamut associated with a color digital image to the gamut of a particular device in a visually pleasing way. The improvement in appearance of the in-gamut reproduction is based on using calculations similar to those used by the human visual system, namely spatial comparisons. The new approach synthesizes a new reproduction image based on spatial comparisons rather than pixel matches. These spatial comparisons are made first at large spatial separations (or smallest multi-resolution image) with the output interpolated to make the old for the next smaller spatial-separation image (multi-resolution image). Ratio, product, reset, average, resize calculations are made to calculate old intermediate image at this spatial separation (image size). The process continues until spatial resolution equals 1.0 (full resolution). Alternatively, rather than using multi-scalar images, ratios are calculated from a single resolution image using increasingly smaller distances within the image. An important aspect of this invention is that instead of calculating the appearance of an image from the radiance found in the scene, it can use both the Goal (original) and the Best images to calculate a resulting new image that has the same spatial comparisons as the original in Media A, within the gamut of Media B. This technique is also helpful when applied to prior spatial comparison methods for images having a limited dynamic range. This invention allows the user to calculate new values for all pixels in an image so as to look like another image with completely different colorimetric values.