Research On The Conversion Model Between CMYK And L~*a~*b~* Color Spaces Based On Digital Proofing

The conversions of color spaces are core technique of color management.The purpose of topic is doing the research about the models of conversion between CMYK and L~*a~*b~* that provides wider theory basis and practical guide on the basis of printing the standard color target ECI2002 obtained from inkjet printer named EPSON STYLUS PRO9800,and choosing the data of building and checking.According to plane theory of four colors,the topic verifies the plane regulation of Digital Proofing paper about four colors by establishment of binary linear regression plane equation built by least-squares method and analyses of equations' correlation and variance.The quadratic curve equations about relation between dot area and the coefficient of each plane equation are built by least-squares method and then are substituted into the coefficient of plane equations. The conversion equations are initially gained.The conversion equations under given K dot areas with 0%,20%,40%,60%,80%from CMYK to L~*a~*b~* color space can be gotten after check of initial conversion equations' accuracy.After the relation between K with 0%,20%,40%,60%,80%and each coefficient of conversion equation are found,the positive conversion equation at every K from CMYK to L~*a~*b~* color spaces are built by using cubic spline interpolation algorithm and the accuracy of equations are analyzed.According the theory of BP and GA-BP Neural Network,the data of building model are differentiated by measuring L~* to train ten BP Neural Network with same structure.Because of the random of initial weights in BP Neural Network,the topic uses GA to research best weights and bios of each BP Neural Network in order to apply to BP Neural Network and to retrain BP Neural Network.Through contrast of BP and GA-BP Neural Network,it can be found that GA-BP is better than BP at training speed and accuracy.At the same time,the reverse conversion models of BP and GA-BP Neural Network are built.The process building conversions of color spaces based on Digital Proofing provides more references for the conversion methods between two color spaces of color management under different printing types,which has practical meaning.