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USING COMPRESSION TO STORE COLOR CORRECTION TABLES

IP.com Disclosure Number: IPCOM000027838D
Original Publication Date: 2000-Feb-29
Included in the Prior Art Database: 2004-Apr-09
Document File: 2 page(s) / 136K

Publishing Venue

Xerox Disclosure Journal

Abstract

A method of storing data association with multidimensional correction tables used in electrophotographic printing machines is disclosed. These tables are often used to convert from one color space to another color space, and in the past have made use of one of several multidimensional interpolation techniques. Interpolation is needed because a 24- bit input (8-bits each for red, green, and blue for example) require (2**8)**3 entries. Current methods store on the order of (2**4)**3 or (2**5)**3 entries, and use interpolation to calculate intermediate values. It is proposed to store the information associated with all 2**24 colors by using a compression on the data.

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XEROX DISCLOSURE JOURNAL

USING COMPRESSION TO STORE COLOR CORRECTION TABLES
Robert J. Rolleston

Proposed Classification
U. S. C1. 399/298 Int. C1. G03g 15/16

A method of storing data association with multidimensional correction tables used in electrophotographic printing machines is disclosed. These tables are often used to convert from one color space to another color space, and in the past have made use of one of several multidimensional interpolation techniques. Interpolation is needed because a 24- bit input (8-bits each for red, green, and blue for example) require (2**8)**3 entries. Current methods store on the order of (2**4)**3 or (2**5)**3 entries, and use interpolation to calculate intermediate values. It is proposed to store the information associated with all 2**24 colors by using a compression on the data.

Color management systems deal with the problem of trying to get the colors correct across a wide variety of devices in a system. This may involve the problem of scanning an image, displaying on a screen, and then printing the image. Because each of the devices associated with this process have their own representation of color, to obtain predictable, quality results, it is desirable to transform the data to and from each device in a controlled fashion. This often means making use of an intermediate device independent representation.

The problem now is how to transform scanner red, green, blue data display red, green, blue data, so the displayed colors are the same as the scanned original colors, and then transform the displayed red, green, and blue colors to a printer's cyan, magenta, and yellow colors, so the print looks the same as what is shown on a monitor, or perhaps the same as on an original copy.

These transformations are often nonlinear, must be empirically derived, and are often not easily modeled using simple transformations such as matrices and transfer functions. It is for these reasons that many systems today use multidimensional look up tables. These look up tables are on the order of 16**3 or 32**3, and values not located on node of the table are calculated by some type of interpolation scheme, such as trilinear, tetrahedral, or prism. The interpolation should be fast, accurate, and realizable in hardware.

Xerox Disclosure Journal - Vol. 25, No. 1 JanuaryEebruary 2000

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USING COMPRESSION TO STORE COLOR CORRECTION TABLES (Cont'd)

The disclosed use of compression to store correction tables avoids use of interpolation and thus, gives an improved accuracy to t...