Display Color Characteristic Analysis And Color Space Conversion Technology Research

The International Color Consortium (ICC) formulated the relative color management standards, in order to meeting accurately communicating and reproducing color information in those systems:opening print system, electronic publishing and network publishing systems. Color display is an important part of the prepress system. And the precision of its colorimetric properties and color space transition model will directly affect the effect of the color images display. Moreover, it can be used for soft-proofing to achieve a real sense of the "What you see is what you get." through display device's color management. Therefore, the color characteristics and color space transition model of display are studied in this thesis.Based on the comprehensive analysis of color management's principle, method, process and key technologies, it designed display color test system, proposed a method of characterizing the non-linear relationship between input and output from the view of perfecting distribution uniformity of sampling points'space to improve the characterization transformation accuracy. An ends-subdivided and middle-uniform test color target is designed based on LOG functional transformation.Through the experiment, quantitative analysis variety color characteristics of display, including display color gamut, channel independence, spatial uniformity, time uniformity, phosphorus powder constancy, LCD screen viewing angle and black spots impact on the color correction, as well as comparison of display effect with printing effects, etc. Visual analyzed gamma value, brightness, color temperature impact to the output effect using the range theory. Based on the above research, self-adaption Dynamic Gamma Function is proposed to improve image's effect, and then a corresponding adjustment process is given. Non-linear regression transformation model is improved effectively using to increase the number of polynomial's items, the constant term, extensions and other methods, in order to solve the accuracy problem, local maximum or minimum error and regulate ability decline of high-return in accuracy. In addition, the conversion from polynomial of RGB color space to Lab color space was achieved by changing the model's output color space. Conversion accuracy was compared which of four kinds of geometric interpolation algorithm in the process of model transformation in three-dimension look-up table. The results show that the color difference of model transformation was less than three which was not sensitive to the human visual range.Based on the study of the relationship between digital drive value and the spectral data, tone/matrix model in color management modeling of display characterization is established by using quadratic polynomial fitting. In the case of big conversion error, changing the feature points from the maximum point into the mid-point can make the chromatic difference reduced significantly, so that the conversion accuracy will be improved.BP neural network conversion models from RGB to Lab and Lab to RGB are established, and color difference estimation method is explored in process of reverse-transformation. The best layer numbers of conversion networks are studied through multiple training. Network's size is decreased by structure decomposing to promote training speed. Training sample, test sample and uniform sample are selected to do comparison so as to realize the requirement of higher accuracy of conversion models. Meanwhile, a method of reverse-transformation from Lab to RGB is proposed based on the forward transformation of neural network and table searching. Experiments verify the reliability and effectiveness of this method.The above research shows that these methods could realize color space transformation of displayer, could satisfy different accuracy requirement of color copy. In which, three-dimension look-up table and neural network conversion models obtained transforming color difference is small, and is a perfect method among kinds of methods relatively. These methods provide theoretical base to realize soft proofing. It is a good foundation and has accumulated practical experience for the further development of such color management systems as scanner, displayer, printer etc.