Abstract: In ISO printing standards, a color difference tolerance of ΔE*ab=5 is used as a threshold. But CIELAB color space is not uniform enough so that the same color difference value represents different color difference sensation in different color area. It is proved that the color difference calculated by CIEDE2000 is closer to the human sensation, so ISO TC130 is discussing the possibility of replacing CIELAB color difference by CIEDE2000. An experiment was conducted, in which the color difference of typical printing colors, CMYKRGB, was calculated and test. The experimental results showed that the color difference tolerance of ΔE*ab=5 is corresponding to 0.95~6.42 by CIEDE2000, with the average of 3.30 ΔE*00. So a color difference tolerance of ΔE*00=3.3 or a somewhat looser value of ΔE*00=3.5 can be adopted as a new tolerance for printing industry.
Abstract: In order that a better analysis and evaluation of the color performance of developed color inks according to the printing requirements could be obtained, every ink will get abundant levels of ink supply amount made by double-channel control method. The max density obtained by the above method represents the color strength of inks. Then Color Management System is applied to building color gamut of matching process inks, and the color gamut represents the replicable color scope in practice. First, color strength of inks was identified by the following methods. Every ink was put respectively in two ink channels of the color printer and the total values of these two channels were applied to controlling the output, obtaining the wedge diagram of the multilevel output of ink supply amount. In the diagram, the max ink supply amount was large enough and the max density could represent the color strength. Because every ink needs a suitable range of the max density and needs to match the others well in practice. Referring to the standard of offset printing, a suitable density value for a certain ink was chose as its max ink supply amount. Second, within the range of the max ink supply amount, the data set of color patch in the characterization software of Color Management System was used to control ink supply amounts. The color patch was overprinted in the color sequences of Y, M, C and K, and ICC Profile was made according to the making process of standard Profile. Color gamut of the inks could be obtained from the Profile by using self-developed computing equipment and be compared with standard printing process. The result shows that the method used in the experiments is feasible and effective. In addition, the inks in the experiments have a large enough color strength and a color gamut satisfying the practical requirements of the color performance of inks in the printing industry.
Abstract: This paper is focused on the color application on map designing in prepress, detailed study is carried out on the color application basic principles for map designing, different data source color conversion and settings, color conversion in designing software, color management and digital proofing, color conversion in prepress workflow, etc. Application and discussions in more detail are put forward on color application in map designing and processing settings in prepress workflow. Gray-value consistency principle is put forward and used in color map designing, and the color application techniques in prepress workflow are summarized. Color map designing efficiency may be raised by appropriate color settings and color conversion control in prepress workflow, and the prepress traps can be avoided caused by irrational color application and conversion in color map designing.
Abstract: It briefly analyzed the disadvantages of ICC (International Color Consortium) color management technology and color management technology based on iCAM (image Color Appearance Model), and then it put forward the thought of multi-spectral color management technology. It specifically designed the basic framework of the multispectral color management, focused on the basic composition and working principle of spectral color management model. Besides it analyzed the composition and basic principle of spectral color gamut mapping framework. Lastly it pointed out the research direction of multispectral color management.
Abstract: The practical applied formula are based on the density measurement in ink trapping characterization methods, but the density measurement is more suitable for detecting single color printing effect. Due to the defects of the testing equipment, the density measurement is not suitable for the evaluation of ink trapping. Chromaticity evaluation method bases on the color difference between the sample color values and the ideal color values to evaluate ink trapping effects, which can characterize better on the ink trapping effects. Research results showed that the density evaluation method has many deficiencies, and Neugebauer equations predict on the chroma evaluation method doesn’t reach an enough precise to get the ideal value about the secondary overprinting, while the color value which is measured by spectroscopic measurement by experimental methods can be used as the ideal color value of the chromaticity evaluation method. Study on the comparison between density evaluation method and chroma evaluation method of ink trapping, the relative conclusions about advantages and disadvantages of different ink trapping characterization methods will be summarized.
Abstract: To expend the printed color gamut is the most important area for today’s print quality. Conventional wide gamut printing technologies utilize six or seven colors. However, these processes increase the complexity and the cost. Therefore, the four-color wide gamut inks are becoming the major development in Taiwan’s printing industry. This study is focused on the print performance study of the four-color wide gamut inks in the domestic market that are complied with the RoHS regulations. In this study Tung-Ming and K+E wide gamut process inks were tested for their print performance. The press control was to comply ISO12647-2 specifications. The test forms were printed on both type 1 and type 2 papers that specified in ISO12647-2. The normal process ink set was also printed to compare with those wide-gamut color ink sets. The result shows that the both wide-gamut ink sets have reached color gamut larger than the ISO12647-2. In this study shows that the domestic normal process ink set can comply the international standard, and the developing wide gamut ink also reach the standard. However, the color characteristics and printability have to test before using these wide gamut color ink sets. With the optimized process control and color management system, the four-color wide gamut inks can produce the best color result on paper.
Abstract: Scanner is the indispensable image acquisition equipment in the prepress system, high quality ICC profile is significant to reflect the color expression of scanner, and the character of ICC profile is influenced in a great extent by the color input target. The subject is to set up the ICC profile by scanning and data processing Kodak IT8.7/2, Goldencolor GCT 3.0 and GretagMacbeth ColorChecker SG, get the influence of each color input target to the scanner color characteristic through the accuracy analysis and color gamut comparison. Research shows that three kinds of color target has its own advantage, Kodak IT8.7/2 has big color gamut, high accuracy, and better reappearance ability, meets the needs of the everyday users; GretagMacbeth ColorChecker SG is good to the reappearance of high saturate manuscript, and its precision is high, applying to recreate natural landscape; Glodencolor GCT 3.0 is of high precision and larger color gamut, but its expression ability is not good enough in the section of high saturation red and magenta, it can produce high quality scanner ICC profile also. Consequently, it should be taken into consideration of the manuscript, color gamut, accuracy and cost-effective factors comprehensively when choosing scanner color target, eventually you get a satisfactory scanning result.
Abstract: ISO 13660(2001) provides definitions and measurement methods for line width, raggedness, large area graininess, darkness, background haze and extraneous marks. The major shortcoming of ISO 13660(2001) is its inability to describe or address the visual significance of most measured values obtained following the proposed procedures. ISO 19751 even though in development will hopefully expand the definition of print attributes which allow for an easier implementation of the measurement. In this paper, Image quality is evaluated on minute details and characteristics that build up a print, using recommended tools and equipment. This case study is an exploratory experiment to evaluate the print quality with changing toner digital printing screen rules and resolutions. This paper compared large area quality attributes of printed images with different screen rulings and resolution and discussed relationship between quantitative values by Noise Power Spectrum (NPS) and perceptive attributes of images portraits in graphic arts applications.
Abstract: A self- environment adaption model for cross-media reproduction of digital image is presented in this paper.This model is used to color conversion, makes image adaptive display according to ambient light changes. Experimental results show that this model can be used in all kinds of image processing systems for the displaying of image, particularly suitable for handheld image display apparatus.
Abstract: With the rapid development of the information technology and digital image copy devices, the information carrier shows off diversified trends. However paper media still play an important role in many areas serving as information carrier, and correspondingly the information security of paper documents faces great challenges. So how to solve the information security problems of paper media has become the hottest research topic. This paper proposes an information hiding method used in printed documents image based on the screen dots modulating shade composed of a large number of randomly arranged screen dots. These dots are classified into coding dots, anchor dots and perturbing dots respectively. Experimental results show that screen dots modulating shade using our method has larger information capacity and also has strong robustness against the attacks of print-scan processes. Moreover, this technology also can be widely used in many other areas, such as anti-counterfeit printing, anti-copy, document content tamper-proofing and document image retrieval etc.