Achille J.-P. Braquelaire

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Color image quantization, the process of reducing the number of colors in a digital color image, has been widely studied for the last fifteen years. The different steps of clustering methods are studied. The methods are compared step by step and some optimizations of the algorithms and data structures are given. A new color space called H1H2H3 is(More)
PURPOSE To prospectively validate the ability of customized three-dimensional (3D) software to enable bronchial tree skeletonization, orthogonal reconstruction of the main bronchial axis, and measurement of cross-sectional wall area (WA) and lumen area (LA) of any visible bronchus on thin-section computed tomographic (CT) images. MATERIALS AND METHODS(More)
Shading has a great impact to the human perception of 3D objects. Thus, in order to create or to deform a 3D object, it seems natural to manipulate its perceived shading. This paper presents a new solution for the software implementation of this idea. Our approach is based on the ability of a user to coarsely draw a shading, under different lighting(More)
Regular trees can he detined by two types of rational exprwions. For these two types w;isolve the star-height problem, i.e., we show how to construct a rational expression of minimal star-height from the minimal graph of the given tree (i.e., the analogue of the minimal deterministic automaton for regular languages). In one case, the minimal starheight is(More)
Representing the regions of a segmented image is an important aspect of image segmentation. Several different models have been proposed to represent the regions of a segmented image but most of them are dedicated to a specific method. Among the non hierarchical models, the model of planar maps with discrete embedding is certainly the most versatile one.(More)
In this paper we present a data structure improving region segmentation of 2D images. This data structure provides an eecient access to the set of pixel of one region. It also provides topological informations like the frontier of a region, the neighbours of a region or the set of regions included in one region. Thanks to this data structure diierent(More)
The aim of this work is to provide a means to approximate the real boundary underlying the discrete boundary of a digitized 2D region. We require that the sampling of the reconstructed boundary be exactly the discrete one. To this end, we propose a new representation of the boundary of a discrete region that we call Euclidean paths. This paper fully(More)
This paper describes two new methods for the reconstruction of discrete surfaces from shading images. Both approaches are based on the reconstruction of a discrete surface by mixing photometric and geometric techniques. The processing of photometric information is based on reflectance maps, which are classic tools of Shape from Shading. The geometric(More)