Lund University Publications
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Lund University Lund University Publications2000-01-01T00:00+00:001dailyImage Segmentation and Labeling Using Free-Form Semantic Annotation
https://lup.lub.lu.se/search/publication/84497869-1395-4fe4-a472-79cbd9dd2bfe
Tegen, AgnesWeegar, RebeckaHammarlund, LinusOskarsson, MagnusJiang, FangyuanMedved, DennisNugues, PierreÅström, Karl2014In this paper we investigate the problem of segmenting images using the information in text annotations. In contrast to the general image understanding problem, this type of annotation guided segmentation is less ill-posed in the sense that for the output there is higher consensus among human annotations. In the paper we present a system based on a combined visual and semantic pipeline. In the visual pipeline, a list of tentative figure-ground segmentations is first proposed. Each such segmentation is classified into a set of visual categories. In the natural language processing pipeline, the text is parsed and chunked into objects. Each chunk is then compared with the visual categories and the relative distance is computed using the word-net structure. The final choice of segments and their correspondence to the chunked objects are then obtained using combinatorial optimization. The output is compared to manually annotated ground-truth images. The results are promising and there are several interesting avenues for continued research.http://lup.lub.lu.se/record/5052492http://dx.doi.org/10.1109/ICPR.2014.396wos:000359818002067scopus:84919946714engpp 2281-2286 (2014)ISSN: 1051-4651Datavetenskap (datalogi)Image Segmentation and Labeling Using Free-Form Semantic Annotationcontributiontobookanthology/conferenceinfo:eu-repo/semantics/conferencePapertextSolving Quadratically Constrained Geometrical Problems using Lagrangian Duality
https://lup.lub.lu.se/search/publication/313a561a-c5b5-4cce-953a-17899c83711e
Olsson, CarlEriksson, Anders P2008In this paper we consider the problem of solving different pose and registration problems under rotational constraints. Traditionally, methods such as the iterative closest point algorithm have been used to solve these problems. They may however get stuck in local minima due to the non-convexity of the problem. In recent years methods for finding the global optimum, based on Branch and Bound and convex under-estimators, have been developed. These methods are provably optimal, however since they are based on global optimization methods they are in general more time consuming than local methods. In this paper we adopt a dual approach. Rather than trying to find the globally optimal solution we investigate the quality of the solutions obtained using Lagrange duality. Our approach allows its to formulate a single convex semidefinite program that approximates the original problem well.http://lup.lub.lu.se/record/1399321http://dx.doi.org/10.1109/ICPR.2008.4761896ISBN: 978-1-4244-2174-9wos:000264729001123scopus:77957935298engpp 2469-2473 (2008)ISSN: 1051-4651MatematikSolving Quadratically Constrained Geometrical Problems using Lagrangian Dualitycontributiontobookanthology/conferenceinfo:eu-repo/semantics/conferencePapertextLocal Refinement for Stereo Regularization
https://lup.lub.lu.se/search/publication/8daec9d8-859e-4a19-9bd4-2fe42f26d207
Olsson, CarlUlén, JohannesEriksson, Anders2014Stereo matching is an inherently difficult problem due to ambiguous and noisy texture. The non-convexity and non- differentiability makes local linear (or quadratic) approximations poor, thereby preventing the use of standard local descent methods. Therefore recent methods are predominantly based on discretization and/or random sampling of some class of approximating surfaces (e.g. planes). While these methods are very efficient in generating a rough surface estimate, via either fusion of proposals or label propagation, the end result is usually not as smooth as desired. In this paper we show that, if the objective function is decomposed correctly, local refinement of candidate solutions can be performed using an ADMM approach. This allows searching over more general function classes, thereby resulting in visually more appealing smooth surface estimations.http://lup.lub.lu.se/record/4777616http://dx.doi.org/10.1109/ICPR.2014.695wos:000359818004032scopus:84919935988engpp 4056-4061 (2014)ISSN: 1051-4651MatematikDatorseende och robotik (autonoma system)Local Refinement for Stereo Regularizationcontributiontobookanthology/conferenceinfo:eu-repo/semantics/conferencePapertextRevisiting Trifocal Tensor Estimation Using Lines
https://lup.lub.lu.se/search/publication/127ea038-ad83-4ab0-8bc5-e65e7543851c
Kuang, YubinOskarsson, MagnusÅström, Karl2014In this paper, we revisit the problem of estimating the trifocal tensor from image line measurements. With measurements of corresponding lines in three views, a linear method [1] requiring 13 lines was developed to estimate the trifocal tensor from which projective reconstruction of the scene is made possible. By further utilizing the nonlinear constraints on the trifocal tensor, we propose several new linear solvers that require fewer number of lines (10,11,12) than the previous linear method. We use methods based on algebraic geometry to incorporate the non-linear constraints in the estimation. We demonstrate the performance of the proposed solvers on synthetic data. We also test the solvers on real images and obtain promising results.http://lup.lub.lu.se/record/5052500http://dx.doi.org/10.1109/ICPR.2014.419wos:000359818002090scopus:84919934810engpp 2419-2423 (2014)ISSN: 1051-4651Datorseende och robotik (autonoma system)MatematikRevisiting Trifocal Tensor Estimation Using Linescontributiontobookanthology/conferenceinfo:eu-repo/semantics/conferencePapertextRobust Camera Tracking by Combining Color and Depth Measurements
https://lup.lub.lu.se/search/publication/3e6cac3a-befc-4dcd-831c-89d52bd3e275
Bylow, ErikOlsson, CarlKahl, Fredrik2014One of the major research areas in computer vision is scene reconstruction from image streams. The advent of RGB-D cameras, such as the Microsoft Kinect, has lead to new possibilities for performing accurate and dense 3D reconstruction. There are already well-working algorithms to acquire 3D models from depth sensors, both for large and small scale scenes. However, these methods often break down when the scene geometry is not so informative, for example, in the case of planar surfaces. Similarly, standard image-based methods fail for texture-less scenes. We combine both color and depth measurements from an RGB-D sensor to simultaneously reconstruct both the camera motion and the scene geometry in a robust manner. Experiments on real data show that we can accurately reconstruct large-scale 3D scenes despite many planar surfaces.http://lup.lub.lu.se/record/7972405http://dx.doi.org/10.1109/ICPR.2014.692wos:000359818004029scopus:84919904459engpp 4038-4043 (2014)ISSN: 1051-4651Datorseende och robotik (autonoma system)Robust Camera Tracking by Combining Color and Depth Measurementscontributiontobookanthology/conferenceinfo:eu-repo/semantics/conferencePapertextA Measure of Septum Shape Using Shortest Path Segmentation in Echocardiographic Images of LVAD Patients
https://lup.lub.lu.se/search/publication/79343b95-f873-4db6-b32c-fafdd7c26c6c
Landgren, MatildaOvergaard, Niels ChristianHeyden, Anders2014Patients waiting for heart transplantation due to a failing heart can get a left ventricular assist device (LVAD) implanted through open chest surgery. The device consists of a pump that pumps blood from the left ventricle into the aorta. To get the correct rotation speed of the pump, the physicians consider a number of measurements as well as a sequence of echocardiographic images. The important information obtained from the images is the shape of the inter-ventricular septum. For instance, if the septum bulges towards the left ventricle the speed is too high and it might harm the right ventricular function. To get a measure of the shape of the septum, which can be incorporated in a decision support system, we perform a segmentation of the septum using a shortest path method. To reduce user interaction, the user only needs to annotate two anchor points in the first frame. They mark the endpoints of the septum and they are tracked through the sequence with our tracking algorithm. After the segmentation the septum is divided into two regions, the one closest to the right ventricle and the one closest to the left ventricle, and the desired measure is the difference between the areas of these regions divided by the total septum area. The performance of the segmentation algorithm is acceptable and the obtained septum measure corresponds in most cases to the assessments from a physician.http://lup.lub.lu.se/record/4882857http://dx.doi.org/10.1109/ICPR.2014.585wos:000359818003089scopus:84919929934engpp 3398-3403 (2014)ISSN: 1051-4651Datorseende och robotik (autonoma system)MatematikA Measure of Septum Shape Using Shortest Path Segmentation in Echocardiographic Images of LVAD Patientscontributiontobookanthology/conferenceinfo:eu-repo/semantics/conferencePapertextPrime Rigid Graphs and Multidimensional Scaling with Missing Data
https://lup.lub.lu.se/search/publication/b96bb484-340b-4fb1-b113-b1096d820dbc
Oskarsson, MagnusÅström, KarlTorstensson, Anna2014In this paper we investigate the problem of embedding a number of points given certain (but typically not all) inter-pair distance measurements. This problem is relevant for multi-dimensional scaling problems with missing data, and is applicable within anchor-free sensor network node calibration and anchor-free node localization using radio or sound TOA measurements. There are also applications within chemistry for deducing molecular 3D structure given inter-atom distance measurements and within machine learning and visualization of data, where only similarity measures between sample points are provided. The problem has been studied previously within the field of rigid graph theory. Our aim is here to construct numerically stable and efficient solvers for finding all embeddings of such minimal rigid graphs. The method is based on the observation that all graphs are either irreducibly rigid, here called prime rigid graphs, or contain smaller rigid graphs. By solving the embedding problem for the prime rigid graphs and for ways of assembling such graphs to other minimal rigid graphs, we show how to (i) calculate the number of embeddings and (ii) construct numerically stable and efficient algorithms for obtaining all embeddings given inter-node measurements. The solvers are verified with experiments on simulated data.http://lup.lub.lu.se/record/5052497http://dx.doi.org/10.1109/ICPR.2014.139wos:000359818000127scopus:84919941117engpp 750-755 (2014)ISSN: 1051-4651MatematikDatorseende och robotik (autonoma system)Prime Rigid Graphs and Multidimensional Scaling with Missing Datacontributiontobookanthology/conferenceinfo:eu-repo/semantics/conferencePapertext