Research On Technology Of Halftoning And Color Management For Digital Printing

With the rapid development of information technology and computer technology,digital printing technology is gradually becoming mature.Accordingly,digital printing is gradually occupying the traditional printing market.Due to its advantages of environmental protection,flexibility,efficiency,fineness,and intelligence,digital printing is undoubtedly the future of the printing industry.The color reproduction accuracy of digital prints is guaranteed through color management,and the conversion algorithms between CIEL~*a~*b~*color space and CMYK color space is a key technology for color management.This thesis has conducted in-depth research on the forward and backward conversion of CIEL~*a~*b~*color space and CMYK color space.In the study of forward conversion,the algorithm based on colorimetric plane theory and the RSPL(Regularized Linear Splines)algorithm used by the famous open-source color management software ArgyllCMS are first analyzed.Based on this,the algorithm based on multilevel B-splines method is proposed.We design an experiment to compare the conversion accuracy of the three.The results show that the conversion accuracy of our algorithm is much higher than that of the algorithm based on colorimetric plane theory,and slightly lower than that of the RSPL algorithm.However,our algorithm is faster than the RSPL algorithm,therefore is more practical in real time application.In the research of the reverse conversion,we analyze the principle of the inverse centroid interpolation algorithm used in ArgyllCMS and test its conversion accuracy.The results show that the conversion accuracy can meet the requirements of the general printed matter.Digital halftoning algorithms determine the quality of the final output image,they are very important in the field of digital printing research.This thesis focuses on the blue noise mask halftoning algorithms.Based on void-and-cluster algorithm and ACBNOM(Algorithm for The Construction of the Blue Noise Mask)algorithm,we propose using direct binary search method to construct blue noise mask.The mask constructed by our algorithm satisfies stacking constraint,has wraparound characteristic and blue noise characteristic and the halftone effect is very close to that of the mask constructed by void-and-cluster algorithm.This paper also studies the construction algorithms of color blue noise mask.An in-depth analysis of the algorithm proposed by Qian of Hewlett-Packard Lab using direct binary search to construct a color blue noise mask is conducted.We found that Qian’s algorithm does not take into account the changing of mean chromaticity caused by the redistribution of ink dot when evaluating the color fluctuation,which leads to a significant degeneration in the halftone image quality.This thesis improves Qian’s algorithm by take into account the changing.Comparing the halftone image generated by Qian’s algorithm and the improved algorithm,it can be seen that the color fluctuation of the latter is lower and shows more delicate visual effect.