Color Degradation of Printed Images

Numerous color images are digitally reproduced today, mainly using the cyan, magenta, yellow and black ink set. The information in a printed image, however, may be distorted or lost due to the image's gradual color degradation as the result of ink fading and diffusion on the substrate. The degradation behavior of the inks can be difficult to predict when catalytic fading is introduced by a variety of ink mixtures produced in the printing process. In this article, we prove that the fading or diffusion rate has an equivalent interpretation as the hazard function in reliability modeling, and the degradation model of printed images with constant fading and diffusion rates can be reformulated as a Markov process model. Hence, the degradation of printed images with time-varying fading and diffusion rates can be modeled as a semi-Markov process. The semi-Markov process model provides a deterministic degradation prediction. We further propose a spatio-temporal Wiener process model for stochastic prediction of the ink fading and diffusion of printed images. Numerical examples and a real-life case study are provided to illustrate the proposed approach.