Packaging is one of the fastest growing segments in the print industry, specifically the digital packaging arena. Color digital printing for corrugated is essentially all inkjet and has existed for at least 20 years. High quality packaging prototyping allows for greater client choice and more short-run finished corrugated products. To exam the color reproduction capability on the corrugated packaging using UV wide-format inkjet printer, a Roland VersaUV LEJ-640 UV LED printer with Eco UV-curable inks was employed in this study. Four print settings were tested on the selected B-flute corrugated boards. The main purposes of this experimental study are to (1) identify the most important factors that influence color reproduction on the corrugated packaging using UV wide-format inkjet printing, (2) exam the process capability of tested print settings, and (3) establish optimum print setting so that the maximum yield of optical density and print contrast could be obtained. It was found that the use of white ink is the most important factor and has a significant effect on the optical density. The print setting of standard mode with white ink is suggested to achieve the maximum yield of optical density and print contrast.
Poor surface color reproduction and incomplete color management system are the main impeding factors for the commercialization of full-color 3D printing. In this paper, the coloration mechanisms as well as characteristics of 3D surfaces were introduced, and a variety of impregnation methods suitable for powder-based 3D printing were integrated. The 24-color cards and four-primary cubes were printed by 3D Systems ProJet 860 Pro printer to compare single-plane and multi-plane optimization effects, choose the best impregnation process and put forward a guide to improve impregnants. The results revealed that the saturation of 3D printing surface color was greatly increased and the brightness was slightly decreased after impregnation process, which reduced chromatic aberration on single-plane or multi-plane. ColorBond and transparent coating spray are the most suitable combination for powder-based 3D objects. Increasing the uniformity, transparency and permeability of coatings is beneficial to further optimize surface colors.
Different reproduction devices can have different sets of reproducible colours. These sets are called gamuts. The process of transforming colours from one device (or image) gamut to another is called gamut mapping. Gamut mapping has many technical issues to be considered: the used colour space, direction and magnitude of the mapping and whether and to which extent ingamut colours should be altered. Spatially invariant algorithms treat all the pixels independently on their position in the image. Spatially variant (local) algorithms allows a better rendition but introduces the problem of artefacts and/or haloing in the resulting image. In this paper we propose a spatially variant gamut mapping algorithm that creates virtually no artefacts nor haloing in the resulting image. We start from an analysis of the Retinex algorithm and devise proper functionals to build an algorithm which tries to maintain spatial ratios in the image while mapping it into the gamut and, at the same time, avoids all drawbacks of Retinex approaches. We suggest to perform the mapping in an RGB colour space rather than one of the perceptually more homogeneous ones. Although less homogeneous, we experimentally show that RGB colour spaces actually have better hue constancy according to a certain criterion.
Error diffusion is an often used method that transforms a continuous tone (multibit) image into an image of lower bit depth, most commonly into a binary output of black and white. The simplicity of the processing and the quality of the output have made error diffusion a frequently used tool. Part of the image quality is attributed to the minimization of quantization errors in the error-diffusion process. This article describes local instabilities in a color multilevel error-diffusion system that—in contrast—can lead to large local errors in the output, far exceeding the normally expected quantization errors. This can have serious negative effects specifically in connection with the design and incorporation of color calibration sheets. © 2016 Society for Imaging Science and Technology.
To improve color reproduction, many printers today use extra colorants, in addition to the traditional four inks (Cyan, Magenta, Yellow and Black). Adding the complementary colorants (Red, Green and Blue) increases the gamut of reproducible colors, while lighter versions of the primary inks can be added to reduce graininess and dot visibility. Using more than three inks introduces colorimetric redundancy in the color separation process, because different ink combinations can reproduce the same target color. When additional inks are introduced, this redundancy rapidly increases, and it is thus crucial to introduce additional constraints in the color separation process, to improve determinacy and to optimize different aspects of print quality. This study focuses on an analysis of the redundancy in the color separation process for an 11-ink printer. It is investigated how the extensive colorimetric redundancy can be utilized to select optimal ink combinations to meet the, sometimes contradictory, criteria of color accuracy, graininess and ink consumption. Analysis of the results of applying different criteria in the color separation process shows that the result heavily depends on the selected criterion. For example, prioritizing graininess will improve print quality by reducing dot visibility, imposing the use of lighter inks, but it will also increase ink consumption.