Alakzatok lineáris deformációinak becslése és orvosi alkalmazásai = Estimation of Linear Shape Deformations and its Medical Applications

A projekt fő eredménye egy általánosan használható, teljesen automatikus alakzat regisztrációs módszer, amely az alábbi tulajdonságokkal rendelkezik: • nincs szükség pontmegfeleltetésekre illetve iteratív optimalizáló algoritmusokra; • képes 2D lineáris és (invertálható) projektív deformációk, valamint 3D affin deformációk meghatározására; • robusztus a geometriai és szegmentálási hibákra; • lineáris időkomplexitású, ami lehetővé teszi nagy felbontású képek közel valós idejű illesztését. Publikusan elérhetővé tettünk 3 demó programot, amelyek a 2D és 3D affin, valamint síkhomográfia regisztrációs algoritmusainkat implementálják. Továbbá kifejlesztettünk egy prototípus szoftvert csípőprotézis röntgenképek illesztésére, amit átadtunk a projektben közreműködő radiológusoknak további felhasználásra. Az eredményeinket a terület vezető konferenciáin ( pl. ICCV, ECCV) illetve vezető folyóiratokban (pl. IEEE Transactions on Pattern Analysis and Machine Intelligence, Pattern Recognition). A projekten dolgozó egyik MSc hallgató második helyezést ért el az OTDK-n. Domokos Csaba PhD fokozatot szerzett, továbbá munkáját Kuba Attila díjjal ismerte el a Képfeldolgozók és Alakfelismerők Társasága. A projekt eredményeiről részletesebb információ a projekt honlapokon található: • http://www.inf.u-szeged.hu/ipcg/projects/AFFSHAPE.html • http://www.inf.u-szeged.hu/ipcg/projects/AffinePuzzle.html • http://www.inf.u-szeged.hu/ipcg/projects/diffeoshape.html | The main achievement of the project is a fully functional automatic shape registration method with the following properties: • it doesn’t need established point correspondences nor the use of iterative optimization algorithms; • capable of recovering 2D linear and (invertible) projective shape deformations as well as affine distortions of 3D shapes; • robust in the presence of geometric noise and segmentation errors; • has a linear time complexity allowing near real-time registration of high resolution images. 3 demo programs are publicly available implementing our affine 2D, 3D and planar homography registration algorithms. Furthermore, we have developed a prototype software for aligning hip prosthesis X-ray images, which has been transfered to collaborating radiologists for further exploitation. Our results have been presented at top conferences (e.g. ICCV, ECCV) and in leading journals (e.g. IEEE Trans. on Patt. Anal. & Mach. Intell., Patt. Rec.). An MSc student working on the project received the second price of the National Scientific Student Conference. Csaba Domokos obtained his PhD degree and his work has been awarded the Attila Kuba Prize of the Hungarian Association for Image Processing and Pattern Recognition. More details about our results can be found at: • http://www.inf.u-szeged.hu/ipcg/projects/AFFSHAPE.html • http://www.inf.u-szeged.hu/ipcg/projects/AffinePuzzle.html • http://www.inf.u-szeged.hu/ipcg/projects/diffeoshape.htm

Deformable 3-D Modelling from Uncalibrated Video Sequences

Submitted for the degree of Doctor of Philosophy, Queen Mary, University of Londo

Optimization in Differentiable Manifolds in Order to Determine the Method of Construction of Prehistoric Wall-Paintings

In this paper a general methodology is introduced for the determination of potential prototype curves used for the drawing of prehistoric wall-paintings. The approach includes a) preprocessing of the wall-paintings contours to properly partition them, according to their curvature, b) choice of prototype curves families, c) analysis and optimization in 4-manifold for a first estimation of the form of these prototypes, d) clustering of the contour parts and the prototypes, to determine a minimal number of potential guides, e) further optimization in 4-manifold, applied to each cluster separately, in order to determine the exact functional form of the potential guides, together with the corresponding drawn contour parts. The introduced methodology simultaneously deals with two problems: a) the arbitrariness in data-points orientation and b) the determination of one proper form for a prototype curve that optimally fits the corresponding contour data. Arbitrariness in orientation has been dealt with a novel curvature based error, while the proper forms of curve prototypes have been exhaustively determined by embedding curvature deformations of the prototypes into 4-manifolds. Application of this methodology to celebrated wall-paintings excavated at Tyrins, Greece and the Greek island of Thera, manifests it is highly probable that these wall-paintings had been drawn by means of geometric guides that correspond to linear spirals and hyperbolae. These geometric forms fit the drawings' lines with an exceptionally low average error, less than 0.39mm. Hence, the approach suggests the existence of accurate realizations of complicated geometric entities, more than 1000 years before their axiomatic formulation in Classical Ages

Using Fourier-based shape alignment to add geometric prior to snakes

International audienceIn this paper, we present a new algorithm of snakes with geometric prior. A method of shape alignment using Fourier coefficients is introduced to estimate the Euclidean transformation between the evolving snake and a template of the searched object. This allows the definition of a new field of forces making the evolving snake to have a shape similar to the template one. Furthermore, this strategy can be used to manage several possible templates by computing a shape distance to select the best one at each iteration. The new method also solves some well-known limitations of snakes such as evolution in concave boundaries, and enhances the robustness to noise and partially occluded objects. A series of experimental results is presented to illustrate performances

Multi-Scale 3D Scene Flow from Binocular Stereo Sequences

Scene flow methods estimate the three-dimensional motion field for points in the world, using multi-camera video data. Such methods combine multi-view reconstruction with motion estimation. This paper describes an alternative formulation for dense scene flow estimation that provides reliable results using only two cameras by fusing stereo and optical flow estimation into a single coherent framework. Internally, the proposed algorithm generates probability distributions for optical flow and disparity. Taking into account the uncertainty in the intermediate stages allows for more reliable estimation of the 3D scene flow than previous methods allow. To handle the aperture problems inherent in the estimation of optical flow and disparity, a multi-scale method along with a novel region-based technique is used within a regularized solution. This combined approach both preserves discontinuities and prevents over-regularization – two problems commonly associated with the basic multi-scale approaches. Experiments with synthetic and real test data demonstrate the strength of the proposed approach.National Science Foundation (CNS-0202067, IIS-0208876); Office of Naval Research (N00014-03-1-0108

Deformable Prototypes for Encoding Shape Categories in Image Databases

We describe a method for shape-based image database search that uses deformable prototypes to represent categories. Rather than directly comparing a candidate shape with all shape entries in the database, shapes are compared in terms of the types of nonrigid deformations (differences) that relate them to a small subset of representative prototypes. To solve the shape correspondence and alignment problem, we employ the technique of modal matching, an information-preserving shape decomposition for matching, describing, and comparing shapes despite sensor variations and nonrigid deformations. In modal matching, shape is decomposed into an ordered basis of orthogonal principal components. We demonstrate the utility of this approach for shape comparison in 2-D image databases.Office of Naval Research (Young Investigator Award N00014-06-1-0661