Color map tables smoothing in a color computer graphics system avoiding

Abstract

A method of smoothing a color lookup table minimizes inappropriate shifts away from gray, at the same time reducing the effect of measurement errors and enabling interpolation between the lookup table data points to be performed efficiently. More particularly, data in a preliminary lookup table, comprising a three-dimensional data array in which a location of each data point is designated by a unique tuple, is smoothed so as to satisfy predetermined constraints. A resulting three-dimensional lookup table relates source device colors and destination device colors in a computer graphics system in which a color image source device and a color image destination device have non-coincident color gamuts. The method is performed by, beginning at a data point representing white and concluding at a data point representing black, comparing a data point representing an adjacent shade of gray to neighboring data points and, if a color component of one or more of the neighboring data points differs in value from the same color component of the data point by more than a predetermined amount, adjusting the value of the color component of the one or more neighboring data points such that the color component of the one or more neighboring data points does not differ in value from the color component of the data point by more than the predetermined amount. Related data points whose tuples differ from a tuple of the data point in only one dimension are then compared to neighboring data points. The foregoing steps are repeated until the entire lookup table has been smoothed.