Abstract: Different monitors have different performances on showing the color characteristics. That is, a specific group of RGB values shows different colors in different monitors and different monitors have different color gamut. In order to study the abilities to show color characteristics among the monitors of Dell, HP, EIZO and IBM, we use PR655 to measure chromatic values of different colors on the monitors above. Then we analyze the Chromatic values .Finally we get differences of the monitors in color gamut, the gradation curves and gray balance as follows. As a result, the color gamut in the monitor of EIZO will be 1/5 larger than that in other monitors, colors of EIZO in Slant red and Slant green have an excellent performance and colors of DELL in blue have a better performance. As for the gradation curves, the RGB channels in the four monitors have shadows compressed and have highlights stretched. As to gray balance, if R, G and B have the same value, the monitor of HP tends to show more blue lights, the monitor of Dell tends to show more yellow and green lights, the monitor of IBM tends to show more blue lights, and the monitor of EIZO slightly tends to show more green lights. In a word, the monitor of EIZO has the best performance in gray balance, IBM is in the second place, Dell is in the third place and HP has the worst performance in gray balance.
Abstract: The properties of iCAM appearance model including the viewing conditions calculation, chroma adaptation transformation, IPT properties computation and perception correlation calculation was studied according to the researches studied in the paper. iCAM color appearance model was proposed as the PCS in this paper and the effects on printing image reproduction and evaluation were studied. The conclusions showed that setting iCAM as the PCS had an important role in improving color conversion accuracy and the high fidelity reproduction quality of printing image.
Abstract: Traditional color reproduction technology based on the Metamerism principle, the disadvantage is that different observer condition leads to different color appearance.To fulfill the color consistency, the spectrum reflectance of the object color sample need to be reconstructed. The principal component analysis makes use of the linear combination of a few principal components to reconstruct the spectral reflectance of sample. This paper analyzes the 31*31 matrix of Munsell spectral data by the principle component analyze method and achieves the principal component for spectrum reflectance. The numbers of principal components are identified as six by discussing the variance contribution rate. Spectral reconstruction of four Munsell testing samples makes use of first six principal components, which has met the accuracy requirements. Research shows that the reconstruction of spectral accuracy decreased when training samples and testing samples belong to the different database.
Abstract: For the fast and exact detection of printing color, we combine the near infrared (NIR) spectroscopy technique with partial least square (PLS) to build the detection model of printing color. Applying the 144 samples of spectral curve which obtained by the near infrared spectroscopy randomly separated into calibration set and validation set, and base on the 120 calibration set data to establish the prediction model of printing color by PLS, then this model is employed for predicting the color of the 24 validation set. The RMSEC of the 24 blocks’ color parameters L*, a*, b*, E are 0.73, 2.26, 3.03 and 1.09 respectively; The RMSEP are 0.97, 2.77, 3.57 and 1.34 respectively. Those results tell that the NIR spectrum and blocks’ color parameters L*, a*, b*, E could accurately establish a quantitative regression model, applying such model also can accurately predict unknown samples, and the results approximate to the original reference data. The use of near infrared spectroscopy to detect the printed matter nondestructively is feasible, and lays the foundation for the further analysis and establishment of printing chroma model.
Abstract: The nature of device color characteristic methods is the mutual conversion of device-dependent color space and device-independent color space. This paper does the comparative study on the robustness of some color space conversion methods which are based on fuzzy control, dynamic subspace divided BP neural network identification method, and fuzzy and neural identification method, by defining the robustness of color space conversion model and evaluation method. The result shows that the device color characteristic methods which are based on fuzzy and neural identification method can make the feature of BP neural network combine with fuzzy control to greatly improve the robustness of model.
Abstract: Spot-color is widely used in modern package printing technology. In order to use of computer techniques in calculation the formula of spot-color, an algorithm of formula calculation for the gravure spot-color was proposed in this paper. Firstly, the spot-color was divided into ten color areas based on the theory of Munsell color system, and in IGT gravure testing system, the color proofs were printed for each color area, according to different ratio of the cyan, magenta, yellow and white ink, in order to gain the data of mathematics modeling. Then, the algorithm of matching spot-color based on Masking Equation was provided, after measuring and analyzing of the proofs. Moreover, the results of experiment in blue color area show that the algorithm, which was proposed, has good accuracy of matching spot-color. Finally, using the C++ programming language and MySQL database, the prototype computer aided gravure spot-color matching system was developed, the results of operation show that the software is available.
Abstract: The accurate reproduction of spot color is a difficult problem in inkjet digital proofing because of the properties of high saturation and out of the gamut of the spot color. A spot color matching method based on preserved high saturation is presented in this paper. The lightness is dealt with compression transform and modification, with the hue angle of the spot color unchanged. By this means, the precise reproduction of saturation of the spot color can be guaranteed to the maximum extent. When applying our method to the spot color matching process, the experiment result shows that, not only the property of high saturation is well preserved, but also the accuracy of spot color reproduction is improved.
Abstract: The research on the color uniformity of the tiled multiple projectors display systems gets more and more attention. In this paper, taking the tiled two-projector display system as a case, the color calibration method based on ICC color management mechanism was proposed and used to achieve the color uniformity the non-overlapping projected region firstly. And the sectoring parabola interpretation algorithm was used to achieve the color uniformity of the overlapping projected region. The research content of this paper includes: ①The ICC profile of the projector based on matrix model was calculated and generated; ②The ICC profile of the projector based on 3-dimensions lookup table model was calculated and generated; ③The color-matching precision of the above two types of ICC profiles were compared by the color space conversion experiment, and the feasibility of color calibration method of the non-overlapping projected region based on ICC mechanism was verified; ④Finally, the feasibility of color calibration method of the overlapping projected region based on sectoring parabola interpretation algorithm was verified by Quest3D development platform.
Abstract: Color image is an information substance with color components, among which exists correlation. In order to investigate the internal relevance of information in color image and to find out the dependence between them, to research the correlation of the color component image is significant. In order to investigate the relationship between the color space and the correlation of the component images, color spaces RGB/ LCH/ LAB/ OHTA/ YCC are selected and the correlation coefficients and cross correlations of the component images are computed and analyzed on MATLAB platform. The Result shows, that the statistical correlation coefficients of component images under RGB color space are the highest, while in OHTA color space the lowest are showed. The correlation coefficients under LAB and LCH are relative lower. In the opposite color spaces, the correlation coefficients of two opposite color components images are higher than the coefficients between the lightness and one of the opposite color component images. For the cross correlation of color component images, it shows a weak negative exponent relationship between pixel distance and cross correlation. The average cross correlation of component images in LCH space is obvious lower than in other spaces, while the levels of cross correlation in other spaces are similar. The relationship between cross correlation and color characteristics of image in RGB color space is closely, while in OHTA space, the difference of cross correlations among component images are usually small. In LCH space, the difference of cross correlations among component images is obvious, the cross correlation among chroma and the other components (lightness and hue) are much lower.
Abstract: This article using the complex spectrum color characteristic values to regulate ink values, hue deviation, gray balance, etc. This method only uses a complex spectrum spectrometer, low price, easy to operate. Its gives the complex spectrum color characteristics to indicate the color physical properties, and has nothing to do with visual psychology, so it is objective, repeatable, and reliable.