Method and apparatus for converting color scanner signals into

Abstract

A method and apparatus for reconstructing a spectrum realizable in a medium from signals of a color scanner, includes the steps of obtaining an initial spectrum using a linear vector-space representation of the medium spectra, projecting the initial spectrum onto a logarithmic vector-space representation of the medium spectra to obtain an initial set of coordinates in the logarithmic vector-space and modifying the initial coordinates in an iterative convergence loop until a solution criterion is met. The solved coordinates are then transformed into spectrum using the logarithmic vector-space representation and subsequently may be transformed into colorimetric values. The method and apparatus of this invention thus enable conversion of color scanner signals into colorimetric values. This is accomplished without modification of the prevailing scanner elements. In one embodiment, the method comprises selecting a specific medium and a specific scanner, constructing a medium model for the selected medium, constructing a scanner model for the selected scanner, iteratively using the media model and the scanner model to solve for a spectral function representative of a color input, and converting the spectral function into a colorimetric value representative of the color input. The method may be performed in a digital processing system including a memory, a processor such as a CPU, a scanner for receiving the medium and scanning the media to provide the color input, and a printer for reproducing the colorimetric value.