Publications by Roger Hersch | EPFL Graph Search

Chat with Graph Search

Ask any question about EPFL courses, lectures, exercises, research, news, etc. or try the example questions below.

DISCLAIMER: The Graph Chatbot is not programmed to provide explicit or categorical answers to your questions. Rather, it transforms your questions into API requests that are distributed across the various IT services officially administered by EPFL. Its purpose is solely to collect and recommend relevant references to content that you can explore to help you answer your questions.

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 mul ...

Visualization of 3D tomographic images by slicing, i.e. by intersecting a 3D tomographic image with a plane having any desired position and orientation is a tool of choice both for learning and for diagnosis purposes. In this project, a parallel Visible Human Slice Web server has been developed, which offers to any Web client the capability of interactively specifying the exact position and orientation of a desired slice and of requesting and obtaining that slice from a 3D tomographic volume, made of either

We propose a new powerful way of synthesizing moire images that enables the creation of dynamically moving messages incorporating text, symbols, and color elements. Moire images appear when superposing a base layer made of replicated base bands and a revealing layer made of a line grating comprising thin transparent lines. Each replicated base band contains the same image, e.g. text or color motifs. Since the base bands and the revealing line grating have similar periods, the revealed moire image is the ima

The Yule-Nielsen modified spectral Neugebauer model enhanced for accounting for ink spreading in the different ink superposition conditions (EYNSN) requires measuring the reflectances of halftone calibration patches in order to compute the ink spreading cu ...

Although Artistic Screening has been designed mainly for performing the creation of graphic designs of high artistic quality, it also incorporates several important anti-counterfeiting features. For example, bank notes or other valuable printed matters produced with Artistic Screening may incorporate both full size and microscopic letters of varying shape into the image halftoning process. In this contribution, we show that frequency modulated screen dots exhibit a strongly position-dependent reproduction b

Multimedia interfaces increase the need for large image databases, capable of storing and reading streams of data with strict synchronicity and isochronicity requirements. In order to fulfill these requirements, the authors consider a parallel image server architecture which relies on arrays of intelligent disk nodes, each disk node being composed of one processor and one or more disks. This contribution analyzes through bottleneck performance evaluation and simulation the behavior of two multi-processor mu

We present a method for hiding images in synthetic videos and reveal them by temporal averaging. We developed a visual masking method that hides the input image both spatially and temporally. Our masking approach consists of temporal and spatial pixel by p ...

A new spectral colour prediction model for a fluorescent ink printed on paper is presented. It is based on our previous work on transparent support 4 and on a new mathematical formalism which generalizes the Kubelka-Munk theory. The printed paper is modelized by means of three matrices: an interface correction matrix, a matrix exponential modelizing the layer which contains the fluorescent ink, and a reflection matrix caracterising the substrate. The interface correction matrix allows to take mul

A moire is an interference pattern that appears when two different periodic structures are overlaid. The image created is extremely sensitive to small variations in the original layers and is thus very interesting for anti-counterfeit protection. We presen ...

By combining a metallic ink and standard inks, one may create printed images having a dynamic appearance: an image viewed under specular reflection may be considerably different from the same image viewed under non-specular reflection. Patterns which are either dark or hidden become highlighted under specular reflection, yielding interesting visual effects. To create such images, one needs to be able to reproduce at nonspecular reflection angles the same colors, by standard inks alone or in combination with

Direct Volume Rendering is a popular technique for visualization of 3D datasets that offers many advantages over other algorithms but requires important computing power. Efficient parallelization is therefore an essential need. Taking advantage of an existing LAN instead of using a dedicated parallel architecture can be a cost-effective solution. However this requires special attention in algorithm design to the specific aspects of a LAN as a parallel computing system (long latency, slow throughput). Beside

Printing with custom inks is useful for extending the gamut of printed images, for creating artistically appealing designs or for providing protection against counterfeiting (security documents). The basic colors we consider, consist of the custom inks, their superpositions and the white paper. Color separation for custom inks requires to determine the relative amounts of the basic colors allowing to render each desired input color. To achieve this goal, one may tetrahedrize the set of basic colors on a giv

Studies two different table-based approaches for the calibration of electronic imaging systems. The first approach, which is the classical one, uses the device-independent CIE-XYZ colorimetric space as an intermediate standard space. Input and output devices such as scanners, displays and printers are calibrated separately with respect to the objective CIE-XYZ space. The calibration process requires establishing a 3D mapping between a scanner's device-dependent RGB space and a device-independent colorimetri

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 fixed predefined dot contours. A user-defined mapping transforms screen elements from screen element definition space to screen element rendition space. Thi

The traditional approach to the parallelization of linear algebra algorithms such as matrix multiplication and LU factorization calls for static allocation of matrix blocks to processing elements (PEs). Such algorithms suffer from two drawbacks: they are very sensitive to load imbalances between PEs and they make it difficult to take advantage of pipelining opportunities. This paper describes dynamic versions of linear algebra algorithms, where subtasks (matrix block multiplication, matrix block LU factoriz

Due to increasing printing accuracies and the possibility of printing several droplets at the same pixel location, there is a renewed interest in dot-on-dot printing models. In the present contribution, we improve a dot-on-dot spectral prediction model rel ...

The present invention relies on the moiré patterns generated when superposing a base layer made of base band patterns and a revealing line grating (revealing layer). The produced moiré patterns comprise an enlargement and a transformation of the individual patterns located within the base bands. Base bands and revealing line gratings may be rectilinear or curvilinear. When translating or rotating the revealing line grating on top of the base layer, the produced moiré patterns evolve smoothly, i.e. they may

To fulfill the requirement of rapid access to huge amounts of uncompressed pixmap image data, a parallel image server architecture is proposed, based on arrays of intelligent disk nodes, with each disk node composed of one processor and one disk. It is shown how images can be partitioned into extents and efficiently distributed among available intelligent disk nodes. The image server's performance is analyzed according to various parameters such as the number of cooperating disk nodes, the sizes of image fi

The Visible Human Slice Server (http://visiblehuman.epfl.ch) started offering its slicing services at the end of June 1998. From that date until the end of May, more than 280'000 slices were extracted from the Visible Man, by laymen interested in anatomy, by students and by specialists. The Slice Server is based one Bi-Pentium PC and 16 disks. It is a scaled down version of a powerful parallel server comprising 5 Bi-Pentium Pro PCs and 60 disks. The parallel server program was created thanks to a computer-a

Multimedia interfaces increase the need for large image databases, capable of storing and reading streams of data with strict synchronicity and isochronicity requirements. In order to fulfil these requirements, we use a parallel image server architecture which relies on arrays of intelligent disk nodes, each disk node being composed of one processor and one or more disks. This contribution analyzes through simulation the real-time behavior of two multiprocessor multi-disk architectures: GigaView and the Uni

Roger Hersch

Chat with Graph Search

Compositional reflectance and transmittance model for multilayer specimens

A Parallel PC-based Visible Human Slice WEB server

Band Moire images

Calibrating the ink spreading curves enhanced Yule-Nielsen modified spectral Neugebauer model with the two-by-two dot centering printer model

Anti-counterfeiting features of artistic screening

Performances of multiprocessor multidisk architectures for continuous media storage

Synthetic electronic video containing a hidden image

Spectral colour prediction model for a transparent fluorescent ink on paper

High-resolution 1D moirés as counterfeit security features

Reproducing color images with embedded metallic patterns

Communication Costs of Parallel Volume Rendering of Large Images on a Network Of Workstations

Visually-based color space tetrahedrizations for printing with custom inks

Two approaches in scanner-printer calibration: colorimetric space-based vs. "closed-loop"

Artistic screening

Performance of CAP-specified linear algebra algorithms

An Ink Spreading Model for Dot-On-Dot Spectral Prediction

Authentication of documents and articles by moire patterns

Parallel storage and retrieval of pixmap images

Visible Human Slice Web Server: A first assessment

Comparing multimedia storage architectures