Pushing the Limits of 3D Color Printing: Error Diffusion with Translucent Materials

Accurate color reproduction is important in many applications of 3D printing, from design prototypes to 3D color copies or portraits. Although full color is available via other technologies, multi-jet printers have greater potential for graphical 3D printing, in terms of reproducing complex appearance properties. However, to date these printers cannot produce full color, and doing so poses substantial technical challenges, from the shear amount of data to the translucency of the available color materials. In this paper, we propose an error diffusion halftoning approach to achieve full color with multi-jet printers, which operates on multiple isosurfaces or layers within the object. We propose a novel traversal algorithm for voxel surfaces, which allows the transfer of existing error diffusion algorithms from 2D printing. The resulting prints faithfully reproduce colors, color gradients and fine-scale details.Comment: 15 pages, 14 figures; includes supplemental figure

Test Targets 3.0: A Collaborative effort exploring the use of scientific methods for color imaging and process control

Test Targets 3.0 focuses on the integration and analysis of a number of input devices, color image renderings with the use of a robust CTP system and a full-fledged web offset press … The first section is a collection of test forms … The second section is a compilation of color management practices by the class. – p. v

Test Targets 4.0: A Collaborative effort exploring the use of scientific methods for color imaging and process control

Test Target 4.0 (TT4.0) is the result of student teamwork to publish a technical journal for a graduate-level course titled: Advance Color Management (Course no. 2081-735-03). Offered by the School of Print Media (SPM) at Rochester Institute of Technology (RIT), the course is a platform to experiment and to realize a new digital imaging paradigm and the dynamics of teamwork.... Team members learn scientific methodology in process control for repeatable color as well as apply ICC-based color management practices in digital workflows. They plan and conduct press run analyses reported in TT4.0, which is printed using facilities available at RIT. In producing this publication, the team learns to integrate design, content creation, digital media, and print production in a seamless workflow.... -p. 4

Test Targets 2.0: A Collaborative effort exploring the use of scientific methods for color imaging and process control

Test Targets 2.0 was a class project in Test Targets for Graphic Art Imaging in the winter quarter of 2001-2 academic year. The objectives were to put together a collection of custom test forms, developed by Professors Robert Chung and Franz Sigg, and to coach students to showcase possible use of these test forms along with associated Microsoft Excel templates for device calibration and process control when implemented in a color managed digital workflow. - p. iv

Using ΔE Distribution as a predictor of digital proofing performance

The performance of color matching in ICC-based Color Management Systems (CMS) is being improved, and its workflow established. As part of the digital workflow, digital proofing plays an important roll in the control of color from capture to the printed page, but its method of evaluation is not clearly understood. To evaluate the degree of color matching by digital proofing in an ICC-based CMS between a reference image and a sample image, the [formula] calculated by averaging the individual color differences is being used. Doing a qualitative evaluation, ICC-based CMS should be able to stand behind the statement that the color space transformation through the Profile Connection Space (PCS) is correlated to visual judgments. The ΔE*a,b Distribution should provide more information than the average [formula] to evaluate the degree of color matching in digital proofing. In this research, the visual judgment between digital proof and a reference image color matches is studied. Using a reference image, and digital proofs as sample images, a psychometric evaluation based on the one-dimensional scaling technique is applied to scale the visual assessments. From the three dimensions: lightness, chroma, and hue; the lightness (L*) dimension was the only aspect addressed to scale the visual assessments. The reference image was generated with the color characterization data for Type 1 printing 1, and digital proofs with the input data characterization of 4-color process printing (IT8.7/3 target)2,3. Those digital proofs were presented to a panel of observers; data were collected, and analyzed to develop a preference scale that represents the qualitative evaluation of the color match. To test the accuracy of the ΔE*a,b Distribution for evaluating the degree of color matching, a quantitative analysis was done. The ΔE*a,b Distribution was analyzed by the cumulative frequency distribution technique between the reference image and the digital proofs, for 182 patches of the IT8.7/3 target, and the best critical value to match the visual scale was obtained. A quantitative evaluation between the digital proofs and the reference image, based on the color characterization data for Type 1 printing 1,4, was used to scale the average [formula] and the ΔE*a,b Distribution. Then, a classical statistical method was applied to those metric scales and to the visual scale to infer that the degree of color matching is better correlated between the visual judgement and the ΔE*a,b Distribution, than between the visual judgement and the average [formula]. Finally, using this method based on the qualitative analysis, a median of the ΔE*a,b Distribution of 52.8% would produce a visual match between the reference and the sample. Endnotes for Abstract ANSI CGATS TR 001-1995 Graphic technology - Color characterization data for Type 1 printing. ISO 12642:1997 Graphic technology - Prepress digital data exchange - Input data for characterization of 4-colour process printing. ANSI IT8.7/3. Graphic technology - Input data for characterization of 4-color process printing. Reston, Virginia. June 21 (1993). ANSI CGATS.6-1995 Graphic technology - Specifications for graphic arts printing Type 1

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

Consistency and Standardization of Color in Medical Imaging: a Consensus Report

This article summarizes the consensus reached at the Summit on Color in Medical Imaging held at the Food and Drug Administration (FDA) on May 8–9, 2013, co-sponsored by the FDA and ICC (International Color Consortium). The purpose of the meeting was to gather information on how color is currently handled by medical imaging systems to identify areas where there is a need for improvement, to define objective requirements, and to facilitate consensus development of best practices. Participants were asked to identify areas of concern and unmet needs. This summary documents the topics that were discussed at the meeting and recommendations that were made by the participants. Key areas identified where improvements in color would provide immediate tangible benefits were those of digital microscopy, telemedicine, medical photography (particularly ophthalmic and dental photography), and display calibration. Work in these and other related areas has been started within several professional groups, including the creation of the ICC Medical Imaging Working Group

TCP throughput guarantee in the DiffServ Assured Forwarding service: what about the results?

Since the proposition of Quality of Service architectures by the IETF, the interaction between TCP and the QoS services has been intensively studied. This paper proposes to look forward to the results obtained in terms of TCP throughput guarantee in the DiffServ Assured Forwarding (DiffServ/AF) service and to present an overview of the different proposals to solve the problem. It has been demonstrated that the standardized IETF DiffServ conditioners such as the token bucket color marker and the time sliding window color maker were not good TCP traffic descriptors. Starting with this point, several propositions have been made and most of them presents new marking schemes in order to replace or improve the traditional token bucket color marker. The main problem is that TCP congestion control is not designed to work with the AF service. Indeed, both mechanisms are antagonists. TCP has the property to share in a fair manner the bottleneck bandwidth between flows while DiffServ network provides a level of service controllable and predictable. In this paper, we build a classification of all the propositions made during these last years and compare them. As a result, we will see that these conditioning schemes can be separated in three sets of action level and that the conditioning at the network edge level is the most accepted one. We conclude that the problem is still unsolved and that TCP, conditioned or not conditioned, remains inappropriate to the DiffServ/AF service

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