Introducing ink spreading within the cellular Yule-Nielsen modified Neugebauer model

We propose an extension of the cellular Yule-Nielsen spectral Neugebauer model accounting for ink spreading of each ink within each subdomain. Characterization of the ink spreading within a given subdomain is performed by fitting the mid-range weights of subdomain node reflectances with the goal of minimizing the sum of square differences between predicted and measured mid-range reflectances. We show that the mid-range weights within a subdomain can be either separately fitted on three halftones or jointly fitted on a single halftone. Accounting for ink spreading considerably improves the prediction accuracy and requires only one additional measurement per subdomain. These additional measurements do not necessarily require spectral measurements. Instead, ink spreading can also be characterized with red, green and blue sensor responses without decreasing the model reflectance prediction accuracy.