Spectral Image Prediction of Color Halftone Prints Based on Neugebauer Modified Spectral Reflection Image Model

As the spectral prediction model for color halftone prints using the microscopic measurement, the conventional spectral reflection image model (SRIM) is extended by introducing the concept of the conventional spectral Neugebauer Model, and a new prediction model, the Neugebauer modified spectral reflection image model (NMSRIM), is proposed. Compared to the SRIM, the NMSRIM abstracts the spatio–spectral transmittance distribution of ink layer using the limited number of base color functions and the spatial position function for each base color function in order to efficiently predict the reflectance of color halftone prints from a small number of measurements. The NMSRIM separately analyzes the mechanical dot gain and the optical dot gain. The NMSRIM can predict not only the spectral reflectance but also the microscopic spatial distribution of reflectance. The spatial distribution of reflectance is related to the appearance of halftone prints. The methods to obtain the parameters of NMSRIM are also proposed. Several parameters are obtained by measurements and the others are obtained by computational estimations. To evaluate the validity of the NMSRIM, the spatio–spectral distribution of reflectance printed with two inks, cyan and magenta (testing data) is predicted from the measurements of the halftone prints printed with one ink, the unprinted paper, and the solid prints of inks which are the cyan, magenta and blue (training data), where the blue corresponds to the combination of cyan and magenta inks. The spectral prediction accuracy was significant since the average and maximum values of ΔE94 in all samples were 0.66 and 1.30, respectively. We also obtained the interesting results according to the spatial prediction accuracy.