Wide-baseline stereo matching is a common problem of computer vision. By the explosion of smartphones equipped with camera modules, many classical computer vision solutions have been adapted to such platforms. Considering the widespread use of various networking options for mobile phones, one can consider a set of smart phones as an ad-hoc camera network, where each camera is equipped with a more and more powerful computing engine in addition to a limited bandwidth communication with other devices. Therefore the performance of classical vision algorithms in a collaborative mobile environment is of particular interest. In such a scenario we expect that the images are taken almost simultaneously but from different viewpoints, implying that the camera poses are significantly different but lighting conditions are the same. In this work, we provide quantitative comparison of the most important keypoint detectors and descriptors in the context of wide baseline stereo matching. We found that for resolution of 2 megapixels images the current mobile hardware is capable of providing results efficiently.

1 aJuhász, Endre1 aTanacs, Attila1 aKato, Zoltan1 aRamponi, Giovanni1 aLončarić, Sven1 aCarini, Alberto1 aEgiazarian, Karen uhttps://www.inf.u-szeged.hu/en/publication/evaluation-of-point-matching-methods-for-wide-baseline-stereo-correspondence-on-mobile-platforms01104nas a2200181 4500008004100000245007200041210006700113260002800180300001400208520046000222100001900682700002300701700002200724700002100746700002000767700002200787856011300809 2013 eng d00aOn Topology Preservation in Triangular, Square, and Hexagonal Grids0 aTopology Preservation in Triangular Square and Hexagonal Grids aTriestebIEEEcSep 2013 a782 - 7873 a

There are three possible partitionings of the continuous plane into regular polygons that leads to triangular, square, and hexagonal grids. The topology of the square grid is fairly well-understood, but it cannot be said of the remaining two regular sampling schemes. This paper presents a general characterization of simple pixels and some simplified sufficient conditions for topology-preserving operators in all the three types of regular grids.

1 aKardos, Péter1 aPalágyi, Kálmán1 aRamponi, Giovanni1 aLončarić, Sven1 aCarini, Alberto1 aEgiazarian, Karen uhttps://www.inf.u-szeged.hu/en/publication/on-topology-preservation-in-triangular-square-and-hexagonal-grids01724nas a2200181 4500008004100000245013300041210006900174260002800243300001400271520095600285100002001241700002001261700002201281700002101303700002001324700002201344856017601366 2013 eng d00aA uniqueness result for reconstructing hv-convex polyominoes from horizontal and vertical projections and morphological skeleton0 auniqueness result for reconstructing hvconvex polyominoes from h aTriestebIEEEcSep 2013 a788 - 7933 aIn this article we study the uniqueness of the reconstruction in a special class of 4-connected hv-convex images, using two projections and the so-called morphological skeleton. Generally, if just the two projections are given, there can be exponentially many hv-convex 4-connected images satisfying them. Knowing the morphological skeleton in addition, we can reduce the number of solutions. In the studied class, the images are defined by two parameters. We show that the uniqueness of their reconstruction depends only on the values of those parameters.

1 aHantos, Norbert1 aBalázs, Péter1 aRamponi, Giovanni1 aLončarić, Sven1 aCarini, Alberto1 aEgiazarian, Karen uhttps://www.inf.u-szeged.hu/en/publication/a-uniqueness-result-for-reconstructing-hv-convex-polyominoes-from-horizontal-and-vertical-projections-and-morphological-skeleton01313nas a2200181 4500008004100000020002300041245006600064210006500130260004000195300001400235520067200249100002000921700002300941700002100964700002200985700001501007856010901022 2011 eng d a978-1-4577-0841-1 00a2D Parallel Thinning Algorithms Based on Isthmus-Preservation0 a2D Parallel Thinning Algorithms Based on IsthmusPreservation aDubrovnik, CroatiabIEEEcSep 2011 a585 - 5903 a

Skeletons are widely used shape descriptors which summarize the general form of binary objects. A technique to obtain skeletons is the thinning, that is an iterative layer-by-layer erosion in a topology-preserving way. Conventional thinning algorithms preserve line endpoints to provide important geometric information relative to the object to be represented. Bertrand and Couprie proposed an alternative strategy by accumulating isthmus points that are line interior points. In this paper we present six new 2D parallel thinning algorithms that are derived from some sufficient conditions for topology preserving reductions and based on isthmus-preservation.

1 aNémeth, Gábor1 aPalágyi, Kálmán1 aLončarić, Sven1 aRamponi, Giovanni1 aSersic, D. uhttps://www.inf.u-szeged.hu/en/publication/2d-parallel-thinning-algorithms-based-on-isthmus-preservation01661nas a2200205 4500008004100000245007100041210006900112260003500181300001400216520096100230100002001191700001801211700001901229700002401248700001701272700002101289700001101310700002001321856011401341 2009 eng d00aObject subsampling strategies to improve computational performance0 aObject subsampling strategies to improve computational performan aSalzburgbIEEE PresscSep 2009 a448 - 4533 aWe investigate object simplification methods based on Centroidal Voronoi Tesselation (CVT) that share the possibility of great speed-ups in various scenarios. We propose Constrained CVT to sample points from the object boundary and the Region-based CVT to be able to subsample lower dimensional objects, as well. Moreover we introduce custom weight functions based on object properties. Thus, wecan be more specific on what are the important parts of the subsampled object. We also list several novel applications corresponding to the theoretical achivements presented. The advantages of applying the subsampling strategies are presented for registration, human detection, and the segmentation of the retinal vascular system, respectively. Quantitative results are shown to check the deterioration of the accuracy with the level of subsampling, and the computational gain. We also make comparisons with other naive (e.g. random) subsampling methods.

1 aHajdú, András1 aVeres, Péter1 aTanacs, Attila1 aHarangozó, Rorland1 aZinterhof, P1 aLončarić, Sven1 aUhl, A1 aCarini, Alberto uhttps://www.inf.u-szeged.hu/en/publication/object-subsampling-strategies-to-improve-computational-performance01748nas a2200181 4500008004100000020002300041245007900064210006900143260003700212300001400249520109300263100002001356700001401376700001601390700001701406700002101423856012201444 2007 eng d a978-953-184-116-0 00aReconstructing some hv-convex binary images from three or four projections0 aReconstructing some hvconvex binary images from three or four pr aIstanbul, TurkeybIEEEcSep 2007 a136 - 1403 aThe reconstruction of binary images from their projections is animportant problem in discrete tomography. The main challenge in this task is that in certain cases the projections do not uniquely determine the binary image. This can yield an extremely large number of (sometimes very different) solutions. Moreover, under certain circumstances the reconstruction becomes NP-hard. A commonly used technique to reduce ambiguity and to avoid intractability is to suppose that the image to be reconstructed arises from a certain class of images having some geometrical properties. This paper studies the reconstruction problem in the class of hv-convex images having their components in so-called decomposable configurations. First, we give a negative result showing that there can be exponentially many images of the above class having the same three projections. Then, we present a heuristic that uses four projections to reconstruct an hv-convex image with decomposable configuration. We also analyze the performance of our heuristic from the viewpoints of accuracy and running time.

1 aBalázs, Péter1 aPetrou, M1 aSaramaki, T1 aErcil, Aytul1 aLončarić, Sven uhttps://www.inf.u-szeged.hu/en/publication/reconstructing-some-hv-convex-binary-images-from-three-or-four-projections00308nas a2200097 4500008004100000245003600041210003600077260003900113300001400152856004400166 2002 eng d00aVirtual Dissection of the Colon0 aVirtual Dissection of the Colon aNew YorkbSpringer-Verlagc2002/// a197 - 209 uhttps://www.inf.u-szeged.hu/en/node/89900808nas a2200109 4500008004100000245007900041210006900120260004200189300001400231520040900245856004400654 2001 eng d00aVirtual Dissection of the Colon Based on Helical CT Data - Can It Be Done?0 aVirtual Dissection of the Colon Based on Helical CT Data Can It aZagrebbUniversity of Zagrebc2001/// a224 - 2293 aColorectal cancer is the third most commonly diagnosed cancer;and colonic polyps are known precursors of that particular cancer. Virtual dissection refers to a display technique for polyp detection based on helical CT data, where the colon is dissected and flattened as on the pathologist's table. The approach and image processing as well as the early experience are described in this paper. uhttps://www.inf.u-szeged.hu/en/node/898