Abstract: An efficient method for gamut clipping based on user-defined constraints on lightness and hue by: a) defining a color gamut surface of an output device using a gamut descriptor; b) specifying a search range based on maximum tolerances for lightness and hue changes; and, c) for each input color data point outside the gamut, mapping the data point to the closest point in a portion of the gamut surface specified by the search range.

Abstract: A device gamut boundary surface in a device independent color space (DICS) is defined by a set of small triangles. Each triangle in the DICS corresponds to a triangle on the surface of a 3D or 4D color cube in a device dependent color space (DDCS). The triangles in the DICS are derived based on a look-up table which can be obtained by measuring a set of color patches produced from the given device. A small set of carefully selected gamut boundary points in the DICS are determined, and their corresponding points or signals on the surface of the color cube in the DDCS are computed. These data are stored in a table called a gamut descriptor. Points in a gamut descriptor can be determined by a convex polyhedral cone inclusion process, and their corresponding points in the DDCS can be determined by triangle interpolation. The gamut descriptor usually includes gamut boundary points at a number of lightness layers along a series of predetermined hue angles.

Abstract: A digital color reproduction apparatus of the type having a scanner for scanning a color image to produce scanner color signals representing the color image, a digital image processor for processing the scanner color signals to produce printer color signals, and a printer responsive to the printer color signals for reproducing the color image is said to be "closed" when the original color image and the reproduced color image are on the same medium. For a closed color reproduction system, the color transform from scanner color signals to printer color signals can be implemented using the tri-linear interpolation based on a 3D calibration lookup table.

Abstract: A method of calibrating a color image reproduction system in the field is provided. The color image reproduction system includes a color input scanner for generating a color digital image, a digital image processor for applying a color transform to the color digital image to produce a transformed color digital image and, and a digital color printer for printing the transformed color digital image.