The Color Rendering project at IBM Almaden Research Center is examining the problem of how to display and
print quality color images. For this work we need a printer calibrated to a device independent color space. In this
paper, we describe a system for printing CIELAB images on a CMYK printer, and focus particularly on calibration
We use tri-linear interpolation to convert CIELAB colors to CMY or CMYK colorants. We obtain the interpolation
table by inverting a tetrahedral linear interpolation of a calibration table constructed by measuring printed
color patches. Since tetrahedral interpolation has a simple analytical inverse, we can produce the inverted table
much more quickly than with the numerical methods needed to invert a multilinear interpolation, even though we
have to measure more patches to obtain the same accuracy.
To cover the full printer gamut, we found it necessary to add some out-of-gamut entries to the inverted interpolation
table. These entries must be obtained by extrapolation, and increase the errors interpolating colors on and near the
To date we have calibrated a DuPont 4Cast to print CIELAB colors using CMY colorants. We discuss our results
with this calibration, how we propose to add black, and how we fit gamut mapping into the processing.