Patent ID: 7430069

Claim:
A method of converting first image data into second image data by using a predetermined conversion element provided in a predetermined image data processing apparatus, said first image data having a plurality of first color components, said plurality of first color components being a spot color and at least one process color, said second image data having a plurality of second color components, each of said plurality of second color components being a process color, said method comprising the steps of: a) acquiring a plurality of first color density values for said plurality of first color components from said first image data; b) reading conversion information from a predetermined storage element, said conversion information including a plurality of conversion factors for obtaining a pseudocolor density value for said spot color; and c) converting said first image data into said second image data, the conversion in said step c) being performed by calculating a plurality of second color density values for said plurality of second color components based on said plurality of first color density values and said plurality of conversion factors, wherein a second color density value H i for a given color component i included among said plurality of second color density values is calculated by H i =P i +S·G i −P i ·S·G i where said given color component i is one of said plurality of second color components, P i is a first color density value for said given color component i included among said plurality of first color density values, G i is a conversion factor for said given color component i included among said plurality of conversion factors, s is a first color density value for said spot color included among said plurality of first color density values, and each of the color density values is defined that a maximum value is “1”.