Study On Color Gamut Mapping Theory And Method Based On Color Appearance Model Of High Fidelity Color Reproduction

Digital color image equipments play a more and more important role in people’s dailylife and industrial production with the development of digital image capturing, displaying andoutputting technologies. However the high fidelity color information reproduction can’t beperformed because the color generation mechanisms, device color spaces and color gamuts ofcolor image equipments are different. As a result, the developments of numerous techniques,such as color printing technique, displaying technique, image analysis technique, computeraided design (CAD), remote medical technique and electronic commerce technique areaffected. Fortunately, color gamut mapping technique of modern color management system isone of the most important techniques to solve the color distortion problems in colorreproduction area. CIE1931XYZ color space and CIE1976L*a*b*color space are proposedas the standard profile connection space (PCS) to keep the color stimulus consistent betweenthe original image and destination image. As the perception of color information wouldchange with different viewing conditions, so the objective of color management system andhigh fidelity color reproduction is to keep the color appearance consistent more than to keepcolor stimulus consistent. CIE1931XYZ color space is not a color appearance model topredict and calculate the perception of color. Although in some occasions CIE1976L*a*b*istaken for a simple color appearance to predict or calculate some perception attributes, such aspsychological lightness, psychological chromaticity and hue, it can’t meet the requirements ofhigh fidelity color reproduction and color cross-media reproduction. Because it has somedisadvantages including spatial nonuniformity, single and settled viewing conditions, weakpredictive ability for color appearance. So it is necessary to study color gamut mapping theoryand method based on color appearance model deeply for high fidelity color reproduction.The contents about color gamut technique which is the key technique in high fidelitycolor reproduction, such as color appearance&color appearance model, color gamut mappingtheory and method and the implementation of high fidelity color reproduction, are studied indetail in this paper. The main researches can be showed as follows:(1) Color appearance phenomena and color appearance models of high fidelity colorreproduction were analyzed and the chromatic adaptation was elaborated. The forward calculation model and the inverse model of CIECAM02, and the calculation process of iCAMimage color appearance model were studied in detail. And the selection of iCAM as thestandard profile connection space was analyzed comprehensively.(2) The color gamut mapping theory and method based on device-to-device were studieddeeply and the research contents including gamut boundary descriptor, the choice of gamutmapping directions, common gamut mapping methods and the influences of mappingfunctions on image contrast were analyzed. Especially, the gamut clipping methods and gamutcompression methods were studied. Furthermore, HPMinΔE algorithm and SGCK algorithmsuggested by CIE were studied.(3) The image color information characteristics were studied and computed based on themechanisms of color appearance model and color gamut mapping theory. In the paper weclassified the image color information characteristics into three types, i.e., gamutcharacteristic, colorimetry characteristic and color appearance characteristic. Our researchesindicated that the adaptabilities to the gamut mapping intentions were different for variousimages with different color information characteristics.(4) The gamut mapping theory and method based on image-to-device were studieddeeply and the frameworks for spatial gamut mapping based on image-to-device weredesigned. And in the framework we proposed two methods were developed, i.e., BilateralFiltering Spatial Adaptive Gamut Mapping, BFSAGM, and Color Appearance and SpatialRelated Color Gamut Mapping, CASRCGM. The images of subjective evaluation and colorpatches of objective evaluation were mapped by the two proposed gamut mapping methods,the HPMinΔE and SGCK. The mapping effects were compared comprehensively. The resultsshowed that the two proposed methods were better than HPMinΔE and SGCK in mappingprecision and color appearance preservation, while more complicated and time consuming.(5) Several methods to extend destination gamut were studied for high fidelity colorprinting. The methods were classified into two types, hard method and soft method. Onespatial color gamut mapping algorithm model was designed and performed. And the factorsaffecting the destination gamut extension were proposed and the related experiments wereperformed. The results showed that the destination gamut could be extended by thecombination of hard methods and soft methods according to the specific requirements of high fidelity color reproduction so that the efficiency of high fidelity color reproduction could beimproved.At last, we summarized the main contents and innovations and we also look to the futurestudy in the area.