Jordi Arnabat

HANS: Controlling Ink-Jet Print Attributes Via Neugebauer Primary Area Coverages

Ink-jet print attributes such as color gamut, grain, and cost are consequences of the materials and printing technology used and of choices made during color management, color separation, and halftoning operation. Traditionally, color separation determines what amounts of the available inks to use for each reproducible color, and halftoning deals with the spatial distribution of inks that also results in the nature of their overprinting. However, using an ink space as a means of communication between color separation and halftoning gives access only to some of the printed patterns that a printing system is capable of and, therefore, only to a reduced range of print attributes. Here, a method, i.e., Halftone Area Neugebauer Separation, is proposed to gain access to all possible printable patterns by specifying relative area coverages of a printing systems Neugebauer primaries instead of only ink amounts. This results in delivering prints with more optimal attributes (e.g., using less ink and giving rise to a larger color gamut) than is possible using current methods.

Sampling Optimization for Printer Characterization by Greedy Search

Printer color characterization, e.g., in the form of an ICC output profile or other proprietary mechanism linking printer RGB/CMYK inputs to resulting colorimetry, is fundamental to a printing system delivering output that is acceptable to its recipients. Due to the inherently nonlinear and complex relationship between a printing systems inputs and the resulting color output, color characterization typically requires a large sample of printer inputs (e.g., RGB/CMYK) and corresponding color measurements of printed output. Simple sampling techniques here lead to inefficiency and a low return for increases in sampling density. While effective solutions have been proposed to this problem very recently, they either do not exploit the full possibilities of the 3-D/4-D space being sampled or they make assumptions about the underlying relationship being sampled. The approach presented here does not make assumptions beyond those inherent in the subsequent tessellation and interpolation applied to the resulting samples. Instead, the tradeoff here is the great computational cost of the initial optimization, which, however, only needs to be performed during the printing systems engineering and is transparent to its end users. Results show a significant reduction in the number of samples needed to match a given level of color accuracy.

3D modeling from turntable sequences using dense stereo carving and multi-view consistency

This paper addresses the problem of reconstructing a 3D model, with texture, from a sequence of images of the object taken from a turntable. Previous approaches have successfully solved the problem either using active interaction techniques, like the laser pen in Immersions LightScribe commercial system or directly relying on objects texture (not implemented commercially). In contrast, we present a general methodology, which combines silhouette carving with dense stereo and multi-view consistency. It functions even in the presence of highlights or lack of texture. Results are presented on real objects with the above-mentioned characteristics.

Document analysis system for automating workflows

When a user places a document in a capture device—copier, multi-functional printer [MFP], or scanner—the user expects good output to be produced regardless of the document type. There are a variety of means to achieve improved output, in which the settings on the copying device are tuned to the content characteristics of the document. These settings can be automated across the range of scanned context extremes from photo (blurring, no snapping) to fully-text (sharpening, aggressive snapping) documents. This procedure is “document auto typing”, and relies on a fast and accurate assessment of the content of the captured image. We herein describe the development of seven distinct systems for document analysis, and through the comparison of these systems arrive at an efficient and accurate document analysis system for automating the copying settings. We discuss the applicability of this method to other automated workflows in document capture.

Efficient color printer characterization based on extended Neugebauer spectral models

In order to print accurate colors on different substrates, color profiles must be created for each specific ink-media combination. We tackled the problem of creating such color profiles from only few color samples, in order to reduce the needed time of operation. Our strategy is to use a spectral reflectance prediction model in order to estimate a large sampling target (e.g. IT8.7/3) from only a small subset of color patches. In particular, we focused on the so-called Yule-Nielsen modified Spectral Neugebauer model, proposing new area coverage estimation, and a prediction of Neugebauer primaries, which can not be directly measured due to ink limiting. We reviewed the basis of such model, interpret it under the perspective of generalized averaging, and derived expressions to decouple optical and mechanical dot gain effects. The proposed area coverage estimations are based on assumptions of the printing process, and characterized through few extra color samples. We tested the models with thermal ink-jet printers on a variety of media, with dye-based and pigment-based inks. The IT8.7/3 target was predicted from 44 samples, with color average accuracy below 4 dE and maximum error below 8 dE, for dye-based inks, which performed better than pigment-based inks.

Qualification of security printing features

This paper describes the statistical and hardware processes involved in qualifying two related printing features for their deployment in product (e.g. document and package) security. The first is a multi-colored tiling feature that can also be combined with microtext to provide additional forms of security protection. The color information is authenticated automatically with a variety of handheld, desktop and production scanners. The microtext is authenticated either following magnification or manually by a field inspector. The second security feature can also be tile-based. It involves the use of two inks that provide the same visual color, but differ in their transparency to infrared (IR) wavelengths. One of the inks is effectively transparent to IR wavelengths, allowing emitted IR light to pass through. The other ink is effectively opaque to IR wavelengths. These inks allow the printing of a seemingly uniform, or spot, color over a (truly) uniform IR emitting ink layer. The combination converts a uniform covert ink and a spot color to a variable data region capable of encoding identification sequences with high density. Also, it allows the extension of variable data printing for security to ostensibly static printed regions, affording greater security protection while meeting branding and marketing specifications.

Computational Print Control

Printing may seem like a dinosaur among today’s imaging technologies, since its roots stretch back to Becquerel’s work that lead to the first color photographs and the first mechanical color reproduction at the end of the nineteenth century. Ten years ago, we then made the fundamental discovery of a new print control domain, where instead of choices about colorant amounts that are akin to the effect of color filters used since the beginning of color printing, print can be specified by the probabilities of colorant combinations, the Neugebauer Primaries. This has led to the ability to print patterns that were previously inaccessible and consequently, by using large-scale computational optimization, to delivering more color gamut, greater ink use efficiency and greater sharpness and detail in print, while using the same materials and printing system as before. This keynote will present the basic principles of the HANS print control paradigm, review the highlights of results obtained using it to date and indicate its potential future developments.