Research Of Color Space Conversion Algorithm Based On Three-dimensional Look-up Table Method

With the continuous improvement of science,technology and people's living standards,color was more and more important in people's daily life.Due to the differences between the color characteristics of devices,the phenomenon of pale color and color cast in the color reproduction process of the image cross-media can be caused,the color quality of the image could be influenced to a certain extent.However,it was expectped that a more realistic and rich color could be reflected between different devices.As the key technology of color management,color space conversion solved the problem of accurate color transmission between different devices.Based on the previous research results,the three-dimensional look-up table method in common ways of color space conversion was showed deeply in this thesis.Using the relevant equipment and software to collect modeling and testing data,the conversion model between RGB color space and CIEL*a*b* color space was established by using these data.The model was evaluated to achieve accurate color reproduction.The main contents of the study were as follows:(1)The present situation and development of color management system were analyzed from two aspects in theory and technology,the research results of color space conversion technology in recent years were summarized.The problem of color distortion in the process of color reproduction was pointed out,the importance of designing color space conversion model was emphasized.(2)Started from the criterion of color space conversion,the concept and classification of common color space were introduced in detail.The concept,application and problems of four methods of color space conversion(model method,polynomial regression method,threedimensional look-up table method and neural network method)were pointed out,which laid a solid theoretical foundation for the establishment of color space conversion model.(3)Based on the idea of enlarging the interval of bright tone and reducing the interval of dark tone in modeling sample,the non-uniform modeling sample was designed by testing and adjusting different test data.The interpolation operation was used to transform the color value from RGB color space to CIEL*a*b* color space.The conversion accuracy of the algorithm was evaluated by using CIELAB 1976,CIE94 and CIE2000 color difference formula.The modeling samples set of(0,12,25,51,102,179,255)was established as an inhomogeneous optimal set of samples.(4)4096 group modeling points and 512 group test points were selected and the three-dimensional look-up table interpolation method was used as the theoretical basis,a method based on cube inner contraction was designed to search eligible points to replace test points step by step,then the RGB value of test points after reverse conversion were calculated to realize the conversion of color value from CIEL*a*b* color space to RGB color space.The conversion accuracy of the algorithm was evaluated by using CIELAB 1976,CIE94 and CIE2000 color difference formula.When n=2,p=18 was optimal,that was,the number of feature points at per side was 18,and 2 unit distances were shrinking along the direction of the central point P each time.(5)The structure design of forward / reverse color space conversion flow and the functional of related modules were expounded.The forward / reverse color space conversion process of LED display was completed in Windows form mode of Microsoft Visual Studio 2012 platform.