Patent ID: 6919975

Claim:
A method for creating a reverse look-up table from a forward look-up table for a color device; the forward look-up table for mapping a color stimulus value in a device dependent color space to a color response value in a device independent appearance color space, indexes to the forward look-up table spanning all possible color stimulus values for the color device, and outputs from the forward look-up table spanning a color gamut of corresponding color response values for the color device; and the reverse look-up table for mapping a color response value in the device independent appearance color space to a color stimulus value in the device dependent color space, indexes to the reverse look-up table spanning beyond the color gamut of color response values for the color device, and outputs from the reverse look-up table spanning beyond all possible color stimulus values for the color device; the method comprising the steps of: populating a first portion of the reverse look-up table, wherein indexes to the first portion comprise color response values that fall within the color gamut of the color device, and wherein the first portion is populated by search and interpolation in the forward look-up table for color stimulus values corresponding to color response values of the indexes to the first portion of the reverse look-up table; and populating a second portion of the reverse look-up table, wherein indexes to the second portion comprise color response values that fall outside of the color gamut of the color device, wherein the second portion is populated by extrapolation from extrapolation color stimulus values, and wherein the extrapolation color stimulus values are found by search and interpolation in the forward look-up table for color stimulus values corresponding to color response values near a boundary of the color gamut.