Print engine color management using customer image content

The production of quality color prints requires that color accuracy and reproducibility be maintained to within very tight tolerances when transferred to different media. Variations in the printing process commonly produce color shifts that result in poor color reproduction. The primary function of a color management system is maintaining color quality and consistency. Currently these systems are tuned in the factory by printing a large set of test color patches, measuring them, and making necessary adjustments. This time-consuming procedure should be repeated as needed once the printer leaves the factory. In this work, a color management system that compensates for print color shifts in real-time using feedback from an in-line full-width sensor is proposed. Instead of printing test patches, this novel attempt at color management utilizes the output pixels already rendered in production pages, for a continuous printer characterization. The printed pages are scanned in-line and the results are utilized to update the process by which colorimetric image content is translated into engine specific color separations (e.g. CIELAB-\u3eCMYK). The proposed system provides a means to perform automatic printer characterization, by simply printing a set of images that cover the gamut of the printer. Moreover, all of the color conversion features currently utilized in production systems (such as Gray Component Replacement, Gamut Mapping, and Color Smoothing) can be achieved with the proposed system

Reproducing wooden and marble patterns using multi-channel ICC profile

Gravure can reproduce a high quality images because of its capacity to lay down ink films of variable thickness, especially for long runs and high color saturation; this aspect provides a very high shadow detail just like photograph. Many organizations have tried to standardize printing like Fogra, ISO, and more. Larger gamut are being built to cover more out-of-gamut colors, but designs, graphics and colorfulness of the products, are limited due to the involvement of several process variables. In publication printing, only four colors of ink are used: yellow, magenta, cyan, and black. CMYK primaries are generally used because the images to be printed have memory colors (blue sky, green grass) or colors that are obtainable within the CMYK gamut. ICC color management helps the user to build ICC profile is to establish which color is produced when a given combination of CMYK dots are printed. However flooring and wooden patterns printing industry, which often uses gravure printing, use non-CMYK primaries because they are better tuned to the limited color space of such patterns. To successfully reproduce these colors, a smaller or customized gamut is selected. Today proprietary software applications are being used for selection and separation of the non-CMYK primaries to obtain the smaller gamut. This research focused on new non proprietary software for selecting primaries and building multi-channel spot color ICC profiles for reproducing the marble and tile patterns

A Study of the color management implementation on the RGB-based digital imaging workflow: digital camera to RGB printers

An RGB (red, green, and blue color information) workflow is used in digital photography today because a lot of the devices digital cameras, scanners, monitors, image recorders (LVT or Light Value Technology), and some types of printers are based on RGB color information. In addition, rapidly growing new media such as the Internet and CD-ROM (Compact Disc-Read-Only Memory) publishing use an RGB -based monitor as the output device. Because color is device-dependent, each device has a different method of representing color information. Each has a different range of color they can reproduce. Most of the time, the range of color, color gamut, that devices can produce is smaller than that of the original capturing device. As a result, a color image reproduction does not match accurately with its original. Therefore, in typical color image reproduction, the task of matching a color image reproduction with its original is a significant problem that operators must overcome to achieve good quality color image reproduction. Generally, there are two approaches to conquer these problems. The first method is trial-and-error in the legacy-based system. This method is effective in a pair-wise working environment and highly depended on a skill operator. The second method is the ICC-based (ICC or International Color Consortium) color management system (CMS) which is more practical in the multiple devices working environment. Using the right method leads to the higher efficiency of a digital photography produc tion. Therefore, the purpose of this thesis project is to verify that ICC-based CMS with an RGB workflow has higher efficiency (better utilized of resource and capacity) than a legacy-based traditional color reproduction workflow. In this study, the RGB workflows from digital cameras to RGB digital printers were used because of the increasing num ber of digital camera users and the advantages of using an RGB workflow in digital pho tography. There were two experimental image reproduction workflows the legacy-based system and the ICC-based color management system. Both of them used the same raw RGB images that were captured from digital cameras as their input files. The color images were modified with two different color matching methods according to each workflow. Then, they were printed out to two RGB digital printers. Twenty observers were asked to evaluate the picture quality as well as the reproduction quality. The results demonstrated that the two workflows had the ability to produce an accept able picture quality reproduction. For reproduction quality aspect, the reproductions of the ICC-based CMS workflow had higher reproduction quality than the legacy-based workflow. In addition, when the time usage of the workflow was taken into account, it showed that the ICC-based CMS had higher efficiency than the legacy-based system. However, many times, image production jobs do not start with optimum quality raw images as in this study; for example, they are under/over exposure or have some defects. These images need some retouching work or fine adjustment to improve their quality. In these cases, the ICC-based CMS with skilled operators can be implemented to these types of production in order to achieve the high efficiency workflow

Innovative color management methods for RGB printing

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (leaf 57).The demand for printing excellent quality images has increased tremendously in parallel to the growth spurts in the digital camera market. Printing good quality images consistently, however, remains a difficult and/or expensive venture despite the numerous advances in color technology and printing. To alleviate these issues, a color compensating software solution was developed to utilize the unique Kikuze calibration chart to improve printer output. The software solution integrates with the windows printing process at the operating system level through a UNIDRV plug-in. The plug-in retrieves the data within the print stream, passes it on to the color compensation engine which corrects the color data by mapping input and output colors obtained via a B-spline interpolation algorithm. The rendered image is re-introduced into the print stream for final printing. The prototype achieved successful results and can be packaged with commercial printers after a few refinements.by Curtis N. Vanderpuije.M.Eng

Implementing an ICC printer profile visualization software

Device color gamut plays a crucial role in ICC-based color management systems. Accurately visualizing a device\u27s gamut boundary is important in the analysis of color conversion and gamut mapping. ICC profiles contain all the information which can be used to better understand the capabilities of the device. This thesis project has implemented a printer profile visualization software. The project uses A2B 1 tag in a printer profile as gamut data source, then renders gamut of device the profile represents in CIELAB space with a convex hull algorithm. Gamut can be viewed interactively from any view points. The software also gets the gamut data set using CMM with different intent to do color conversion from a specified printer profile to a generic lab profile (short for A2B conversion) or from a generic CIELAB profile to a specified printer pro file and back to the generic CIELAB profile (short for B2A2B). Gamut can be rendered as points, wire frame or solid surface. Two-dimension a*b* and L*C* gamut slice analytic tools were also developed. The 2D gamut slice algorithm is based on dividing gamut into small sections according to lightness and hue angle. The point with maximum chroma on each section can be used to present a*b* gamut slice on a constant lightness plane or L*C* gamut slice on a constant hue angle plane. Gamut models from two or more device profiles can be viewed in the same window. Through the comparison, we can better understand the device reproduction capacities and proofing problems. This thesis also explained printer profile in details, and examined what gamut data source was the best for gamut visualization. At the same time, some gamut boundary descriptor algorithms were discussed. Convex hull algorithm and device space to CIELAB space mapping algorithm were chosen to render 3D gamut in this thesis project. Finally, an experiment was developed to validate the gamut data generated from the software. The experiment used the same method with profile visualization software to get gamut data set source from Photoshop 6.0. The results of the experiment were showed that the data set derived from visualization software was consistent with those from Photoshop 6.0

Test targets 5.0: A Collaborative effort exploring the use of scientific methods for color imaging and process control

Test Targets is about scholarship that intimately involves faculty and students in the process of writing and publishing. It is a collection if research papers that require collaborative effort over a time span of three academic quarters. Initially, students learned metrology, color management system, and the use of test targets for device optimization and process control. As time goes by, students are encouraged to identify research topics, formulate methodologies, and carry out experiments and data analyses in order to have specific findings. - p.

N-colour separation methods for accurate reproduction of spot colours

In packaging, spot colours are used to print key information like brand logos and elements for which the colour accuracy is critical. The present study investigates methods to aid the accurate reproduction of these spot colours with the n-colour printing process. Typical n-colour printing systems consist of supplementary inks in addition to the usual CMYK inks. Adding these inks to the traditional CMYK set increases the attainable colour gamut, but the added complexity creates several challenges in generating suitable colour separations for rendering colour images. In this project, the n-colour separation is achieved by the use of additional sectors for intermediate inks. Each sector contains four inks with the achromatic ink (black) common to all sectors. This allows the extension of the principles of the CMYK printing process to these additional sectors. The methods developed in this study can be generalised to any number of inks. The project explores various aspects of the n-colour printing process including the forward characterisation methods, gamut prediction of the n-colour process and the inverse characterisation to calculate the n-colour separation for target spot colours. The scope of the study covers different printing technologies including lithographic offset, flexographic, thermal sublimation and inkjet printing. A new method is proposed to characterise the printing devices. This method, the spot colour overprint (SCOP) model, was evaluated for the n-colour printing process with different printing technologies. In addition, a set of real-world spot colours were converted to n-colour separations and printed with the 7-colour printing process to evaluate against the original spot colours. The results show that the proposed methods can be effectively used to replace the spot coloured inks with the n-colour printing process. This can save significant material, time and costs in the packaging industry