Patent ID: 7263218

Claim:
A method for creating a look-up table which converts color image data from a device-dependent color space to a device-independent color space, the method comprising the steps of: determining an upper black component value which is a predetermined amount above a target black component value of a device-dependent target data point, and a lower black component value which is a predetermined amount below the target black component value of the device-dependent target data point; accessing a color measurement data table which contains device-independent component values in respective correspondence to device-dependent data points; selecting, from the color measurement data table, an upper set of device-dependent data points which are within the vicinity of the device-dependent target data point at the upper black component value, and a lower set of device-dependent data points which are within the vicinity of the device-dependent target data point at the lower black component value; creating a first new set of device-dependent data points, each of which having a black component value equal to the upper black component value and having a combination of color component values corresponding to a respective one of the selected lower set of device-dependent data points; creating a second new set of device-dependent data points, each of which having a black component value equal to the lower black component value and having a combination of color component values corresponding to a respective one of the selected upper set of device-dependent data points; interpolating, for each of the first new set of device-dependent data points, device-independent component values that correspond to immediately adjacent device-dependent data points from the selected upper set of device-dependent data points, to obtain an interpolated device-independent data point at the upper black component level; interpolating, for each of the second new set of device-dependent data points, device-independent component values that correspond to immediately adjacent device-dependent data points from the selected lower set of device-dependent data points, to obtain an interpolated device-independent data point for the corresponding new device-dependent data points; and interpolating between the device-independent component values which correspond to each of the selected upper set of device-dependent data points, the first new set of device-dependent data points, the selected lower set of device-dependent data points and the second new set of device-dependent data points, to obtain an interpolated device-independent data point corresponding to the device-dependent target data point.