The Peripheral Systems Lab aims at creating and exploring new paradigms in fields related to color imaging and media servers. The main focus of our research is directed towards novel imaging techniques (color prediction models, color reproduction, artistic imaging, moiré theory and images, anti-counterfeiting). We are also creating new paradigms for exploring human anatomy (Visible Human) and are developing a fault-tolerant framework for the creation of non-trivial parallel programs running on clusters of PCs.
We have developed several spectral prediction models for predicting the spectra of halftone patches. They work well for offset prints, thermal transfer and ink-jet printers, see also [Emmel00]. These models take into account the most important physical phenomena such as surface reflections, internal Fresnel reflections at the paper-air interface, light propagation within the paper bulk and ink spreading. Advanced color separation and halftoning techniques have been developed for protecting documents printed with custom inks [Ostromoukhov99a], [Chosson01] or with metallic inks [Hersch03]. In order to facilitate the creation of banknote designs to be printed with non-standard inks, we have also explored techniques for the gamut reduction of color images [Chosson02].
Microstructure imaging enables synthesizing images incorporating visually appealing microstructures. Microstructures are graphic objects specially designed to convey their own message. The microstructure encrustation techniques we have developed rely on the automatic creation of dither matrices or on chromatic color differences [Rudaz04]. Microstructures can be seen by the naked eye, by a magnifying glass or as a moiré revealed by a dot screen or a micro-lens array. Microstructures are being used by the industry for producing remotely printable secure event entry and travel tickets.
The Moiré Phenomenon
A thorough Fourier-based model of the moiré phenomenon has been established, which can be used for both the analysis and synthesis of moiré effects. It provides a full qualitative and quantitative understanding of the moiré effect and has been applied to document authentication and anti-counterfeiting. The book, The Theory of the Moiré Phenomenon by I. Amidror (published by Kluwer Academic Publishers, 1999) provides a comprehensive introduction to the moiré theory and includes our main research results.
High-performance imaging servers
We created a framework for facilitating the development of parallel applications on PC clusters [Gerlach03]. This framework allows to define dynamic parallel schedules (DPS) , which support compositional customizable split-compute-merge graphs of operations (directed acyclic flow graphs). The graphs and the mapping of operations to processing nodes are specified dynamically at runtime. DPS applications can call parallel services exposed by other DPS applications, enabling the creation of reusable parallel components. Currently a version of DPS supporting graceful degradation in case of node failures is being developed. This fault-tolerant version of DPS should become available in spring or summer 2005. Applications include the Visible Human Server running on PCs offering real-time slicing [Gerlach02], anatomic organ construction and visualization [Evesque02] as well as the specification, extraction and flattening of curved surfaces [Saroul03].
Methods were developed for the generation of perceptually-tuned grayscale characters improving the readability of LCD displays. Methods have also been created for generating typographic characters made of parametrisable components. The component-based font synthesizing system enables generating fonts with variations in condensation, weight and contrast [Hu01]. Since fonts are merely described by parameters, they require an order of magnitude less storage space than conventional outline based font descriptions. The book Visual and technical Aspects of Type gives information about various typographic issues.
Director: Prof. Roger D. Hersch (+41 21 693 43 57 ou RD.Hersch@epfl.)
Secretariat: Ms Fabienne Allaire (+41 21 693 66 45)
Fax: +41 21 693 66 80
The Peripheral Systems Laboratory is part of the School of Computer and Communication Sciences of the Ecole Polytechnique Fédérale de Lausanne.