Evaluation of color descriptors for projector-camera systems

International audienceSpatial Augmented Reality applications generally use projector-camera systems to control the visual projection appearance by comparing the initial projected and the acquired images. To obtain an accurate geometric compensation, a non-intrusive feature-point matching approach can be exploited which must handle complex photometric distortions due to the spectral devices responses, complex illumination and the mixing of the projected image with the projection surface.This paper first discusses the invariance properties of existing color descriptors in that application for non-intrusive geometric compensation. Their performance is evaluated using the framework of Setkov et al. (2013) extended by adding the several new test cases: modeled synthetic projections, real-world projections under various illuminants on one and two planar surfaces. Our experimental results show two main conclusions: (1) classical color vision models are hardly suitable to model the distortions in a projector-camera system, and (2) the LHE-based descriptor (Local Histogram Equalization) is the most reliable to compensate real-projections

HTRI: High Time Range Imaging

International audienceIn the same vein as HDRI, we have developed a new approach to image fusion from a seriesof photographs of the same scene taken at different timestamps. When compared with HDRI, exposurebracketing at a single timestamp is replaced by timestamp variation disregarding exposure times.This technique is called HTRI (High Time Range Imaging), it aims at capturing ephemeral eventsoccurring over a long time period during which a sequence of images is shot.For each pixel location, the most salient colors are privilegedin the series of photographs, based on the existing admitted definitions of visual attention.Then, salient moving objects are automatically detected, without introducing a significant amount ofnoise, and despite the large illumination changes that may occur in the acquisition conditions from oneframe to the next. Experiments evaluate the impact of the method parameters, and show differentpossibilities offered by the method

Gardien du Temple: An Interactive Installation Involving Poetry, Performance and Spatial Augmented Reality

International audienc

DAcImPro: A novel database of acquired image projections and its application to object recognition

International audienceProjector-camera systems are designed to improve the projection qual-ity by comparing original images with their captured projections, which is usuallycomplicated due to high photometric and geometric variations. Many researchworks address this problem using their own test data which makes it extremelydifficult to compare different proposals. This paper has two main contributions.Firstly, we introduce a new database of image projections that, covering photo-metric and geometric conditions and providing data for ground-truth computa-tion, can serve to evaluate different algorithms in projector-camera systems. Sec-ondly, a new object recognition scenario from acquired projections is presented,which could be of a great interest in such domains, as home video projections andpublic presentations. We show that the task is more challenging than the classicalrecognition problem and thus requires additional pre-processing, such as colorcompensation or projection area selectio

e-ASTROGAM mission: a major step forward for gamma-ray polarimetry

International audiencee-ASTROGAM is a gamma-ray space mission proposed for the fifth medium-size mission (M5) of the European Space Agency. It is dedicated to the study of the nonthermal universe in the photon energy range from ∼0.15  MeV to 3 GeV with unprecedented sensitivity and angular and energy resolution, together with a ground-breaking capability for gamma-ray polarimetric measurements over its entire bandwidth. We discuss here the main polarization results expected at low energies, between 150 keV and 5 MeV, using Compton interactions in the e-ASTROGAM instrument, from observations of active galactic nuclei, gamma-ray bursts, microquasars, and the Crab Pulsar and Nebula. The anticipated performance of the proposed observatory for polarimetry is illustrated by simulations of the polarization signals expected from various sources. We show that polarimetric analyses with e-ASTROGAM should provide definitive insight into the geometry, magnetization, and content of the high-energy plasmas found in the emitting sources, as well as on the processes of radiation of these plasmas

INTEGRAL results on gamma-ray bursts and polarization of hard X-ray sources

International audienceIn this paper we first review the results obtained by the INTEGRAL mission in the domain of Gamma-Ray Bursts (GRBs), thanks to the INTEGRAL Burst Alert System, which is able to deliver near real-time alerts for GRBs detected within the IBIS field of view. More than 120 GRBs have been detected to date and we summarize their properties here. In the second part of this review we focus on the polarimetric results obtained by IBIS and SPI on GRBs and Galactic compact objects