Roger D. Hersch

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Artistic screening is a new image reproduction technique incorporating freely created artistic screen elements for generating halftones. Fixed predefined dot contours associated with given intensity levels determine the screen dot shape’s growing behavior. Screen dot contours associated with each intensity level are obtained by interpolation between the(More)
Dot gain is different when dots are printed alone, printed in superposition with one ink or printed in superposition with two inks. In addition, the dot gain may also differ depending on which solid ink the considered halftone layer is superposed. In a previous research project, we developed a model for computing the effective surface coverage of a dot(More)
Undesired moiré patterns may appear in colour printing for various reasons. One of the most important reasons is interference between the superposed halftone screens of the different primary colours, due to an improper alignment of their frequencies or orientations. In this article we explain the superposition moiré phenomenon using a spectral model which(More)
A multi-color dithering algorithm is proposed, which converts a barycentric combination of color intensities into a multi-color nonoverlapping surface coverage. Multi-color dithering is a generalization of standard bi-level dithering. Combined with tetrahedral color separation, multi-color dithering makes it possible to print images made of a set of(More)
A spectral colour prediction model is proposed and applied to an ink jet printer. We limit the field of investigation to transparent inks printed on a transparent substrate. The proposed method is based on the computation of the transmittance spectra of colour primaries applying Beer’s law, and on the calculation of their respective surface coverage using a(More)
We propose a new approach for developing parallel I/Oand computeintensive applications on distributed memory PC. Using the CAP Computer-Aided Parallelization tool, application programmers create separately the serial program parts and express the parallel behavior of the program at a high level of abstraction. This highlevel parallel program description(More)
The proposed new spectral reflection model enhances the classical Clapper-Yule model by taking into account the fact that proportionally more incident light through a given colorant surface is reflected back onto the same colorant surface than onto other colorant surfaces. It comprises a weighted mean between a component specifying the part of the incident(More)
A new technique for building stochastic clustered-dot screens is being proposed. A large dither matrix comprising thousands of stochastically laid out screen dots is constructed by first laying out the screen dot centers. Screen dot centers are obtained by placing discrete disks of a chosen radius at free cell locations when traversing the dither array(More)
©2002, IS&T—The Society for Imaging Science and Technology der the microscope. This approach lead to accurate color predictions but it has two major drawbacks: firstly, the simulated dot shapes are not realistic; secondly, the number of different configurations and the number of enlargement coefficients increases dramatically with the number of ink layers.(More)
We propose a compositional model for predicting the reflectance and the transmittance of multilayer specimens composed of layers having possibly distinct refractive indices. The model relies on the laws of geometrical optics and on a description of the multiple reflection-transmission of light between the different layers and interfaces. The highly complex(More)