Apple Inc.

Robin D Myers

Konstantin Othmer

Keith McGreggor

Robert G Johnson, Jr

A method and system for matching color displayed by source and destination display devices and particularly for providing color matching between a computer monitor and an ink printer. The technique of the present invention initially determines the combination and color value ratios of single destination color components that will cause the destination device to display a color that essentially matches each of fully saturated single and dual colors of a source display device. These combinations of single destination color components and their corresponding color value ratios determine the best available blends of destination device color components for printing source device colors. A color matching algorithm is employed to derive the color value ratios&mdash;one for each of the single destination color components. Each color component ratio is then scaled and linearly interpolated over a range defined by the color matching algorithm to generate a set of look-up tables (LUTs)&mdash;one for each single destination color component. Color matching is performed by 1) performing a first series of computational steps to translate the source color value into an intermediate color value which is expressed in terms of single destination color components, 2) accessing the set of LUTs with the intermediate color value obtained in step 1 to obtain a second color value composed of the scaled linearly interpolated color values stored in the LUTs, and 3) optionally performing a second series of computational steps to translate the second color value into a color value which is expressed in terms of the original source color components.

Method and system for color matching between digital display devices

A method and system for matching color displayed by source and destination display devices and particularly for providing color matching between a computer monitor and an ink printer. The technique of the present invention initially determines the combination and color value ratios of single destination color components that will cause the destination device to display a color that essentially matches each of fully saturated single and dual colors of a source display device. These combinations of single destination color components and their corresponding color value ratios determine the best available blends of destination device color components for printing source device colors. A color matching algorithm is employed to derive the color value ratios&mdash;one for each of the single destination color components. Each color component ratio is then scaled and linearly interpolated over a range defined by the color matching algorithm to generate a set of look-up tables (LUTs)&mdash;one for each single destination color component. Color matching is performed by 1) performing a first series of computational steps to translate the source color value into an intermediate color value which is expressed in terms of single destination color components, 2) accessing the set of LUTs with the intermediate color value obtained in step,to obtain a second color value composed of the scaled linearly interpolated color values stored in the LUTs, and 3) optionally performing a second series of computational steps to translate the second color value into a color value which is expressed in terms of the original source color components.

A method and system for matching color displayed by source and destination display devices and particularly for providing color matching between a computer monitor and an ink printer. The technique of the present invention initially determines the combination and color value ratios of single destination color components that will cause the destination device to display a color that essentially matches each of fully saturated single and dual colors of a source display device. These combinations of single destination color components and their corresponding color value ratios determine the best available blends of destination device color components for printing source device colors. A color matching algorithm is employed to derive the color value ratios--one for each of the single destination color components. Each color component ratio is then scaled and linearly interpolated over a range defined by the color matching algorithm to generate a set of look-up tables (LUTs)--one for each single destination color component. Color matching is performed by 1) performing a first series of computational steps to translate the source color value into an intermediate color value which is expressed in terms of single destination color components, 2) accessing the set of LUTs with the intermediate color value obtained in step 1 to obtain a second color value composed of the scaled linearly interpolated color values stored in the LUTs, and 3) optionally performing a second series of computational steps to translate the second color value into a color value which is expressed in terms of the original source color components.

A color matching system initializes a translator by storing profiles of source and destination color devices which include the coordinates in a calibrated color space of the colorants produced in the source and destination devices and a tonal reproduction curve for each device. Mixing equations and parameters are precomputed to be used in matching calculations of an image including color pixels to be matched. The color gamut is divided into mixing regions in which a given point can be produced by a mixture of two chromatic colorants and the achromatic colorants of the destination device. A technique for selecting a mixing region is included which is based on the slopes of vectors defining the colorants of the destination device, and the sample color to be produced. Colors that are out of the gamut of the destination device are adjusted according to precomputed parameters in order to preserve the lightness, chromaticity, or other selected characteristics of the sample color as suits the need of a particular application. The system is particularly suited for computer systems independent of the source and destination devices to be used, and can be adapted to run with a translation cache to enhance the speed of operation of translating a color image on one device for display on a second device.

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Pleasanton, CA, United States of America

Robin D Myers