1,721,257 research outputs found
Tecnologie informatiche e multimediali per la comunicazione e la didattica
No full textIntroduzione alle tecnologie web e multimediali per le facoltà umanistich
Matching techniques to compute image motion
Full text linkThis paper describes a thorough analysis of the pattern matching techniques used to compute image motion from a sequence of two or more images. Several correlation/distance measures are tested, and problems in displacement estimation are investigated. As a byproduct of this analysis, several novel techniques are presented which improve the accuracy of flow vector estimation and reduce the computational cost by using filters, multi-scale approach and mask sub-sampling. Further, new algorithms to obtain a sub-pixel accuracy of the flow are proposed. A large amount of experimental tests have been performed to compare all the techniques proposed, in order to understand which are the most useful for practical applications, and the results obtained are very accurate, showing that correlation-based flow computation is suitable for practical and real-time applications.247–260Pubblicat
Irradiance Preserving Image Interpolation
No full textIn this paper we present a new image up scaling (single image super resolution) algorithm. It is based on the refinement of a simple pixel decimation followed by an optimization step maximizing the smoothness of the second order derivatives of the image intensity while keeping the sum of the brightness values of each subdivided pixel (i.e. the estimated irradiance on the area) constant. The method is physically grounded and creates images that appear very sharp and with reduced artifacts. Subjective and objective tests demonstrate the high quality of the results obtaine
The use of optical flow for the analysis of non-rigid motions
No full textThis paper analysis the 2D motion field on the image plane produced by the 3D motion of a plane undergoing simple deformations. When the deformation can be represented by a planar linear vector field, the projected vector field, i.e., the 2D motion field of the deformation, is at most quadratic. This 2D motion field has one singular point, with eigenvalues identical to those of the singular point describing the deformation. As a consequence, the nature of the singular point of the deformation is a projective invariant. When the plane moves and experiences a linear deformation at the same time, the associated 2D motion field is at most quadratic with at most 3 singular points. In the case of a normal rototranslation, i.e., when the angular velocity is normal to the plane, and of a linear deformation, the 2D motion field has one singular point and substantial information on the rigid motion and on the deformation can be recovered from it. Experiments with image sequences of planes moving and undergoing linear deformations show that the proposed analysis can provide accurate results. In addition, experiments with deformable objects, such as water, oil, textiles and rubber show that the proposed approach can provide information on more general 3D deformations
Scale space graph representation and kernel matching for non rigid and textured 3D shape retrieval
No full textIn this paper we introduce a novel framework for 3D object retrieval that relies on tree-based shape representations (TreeSha) derived from the analysis of the scale-space of the Auto Diffusion Function (ADF) and on specialized graph kernels designed for their comparison. By coupling maxima of the Auto Diffusion Function with the related basins of attraction, we can link the information at different scales encoding spatial relationships in a graph description that is isometry invariant and can easily incorporate texture and additional geometrical information as node and edge features. Using custom graph kernels it is then possible to estimate shape dissimilarities adapted to different specific tasks and on different categories of models, making the procedure a powerful and flexible tool for shape recognition and retrieval. Experimental results demonstrate that the method can provide retrieval scores similar or better than state-of-the-art on textured and non textured shape retrieval benchmarks and give interesting insights on effectiveness of different shape descriptors and graph kernels
“Distributed quantitative evaluation of 3D patient specific arterial models”
No full textIn this paper we describe a new system for the 3D reconstruction and distribution on the net of models for vessels structures. The system is specifically designed to support measurements of medical interest. We describe 2D and 3D segmentation methods implemented and the procedure used to build interactive VRML97 models. The experimental section presents a comparison between segmentation methods, and a first application to surgical planning for endovascular repair of Abdominal Aortic Aneurysms
TESTIMAGES: A Large Data Archive For Display and Algorithm Testing
No full textAn underestimated and time-consuming activity for researchers involved in image processing, computer graphics, display quality analysis, and perception testing is the preparation of a good set of images to be used in the experiments. These images not only need to fit specific technical requirements, but also need to be free from licensing and copyright issues. In order-to-provide easy-to-use solutions for a wide range of testing needs, we developed the TESTIMAGES archive, a huge and free collection of digital images designed for analysis and quality assessment of different kinds of displays (i.e., monitors of different sizes, projectors) and image processing techniques. The archive includes several million images originally acquired and divided into four different categories: SAMPLING and SAMPLING_PATTERNS (aimed at testing resampling algorithms), COLOR (aimed at testing color rendering on different displays), and PATTERNS (aimed at testing the rendering of standard geometrical patterns). The TESTIMAGES archive can be freely downloaded from http://files.testimages.org and used for practical tasks such as monitor calibration and shader testing, as well as for scientific research
Vascular Modeling from Volumetric Diagnostic Data: A Review
Full text linkReconstruction of vascular trees from digital diagnostic images is a challenging task in the development of tools for simulation and procedural planning for clinical use. Improvements in quality and resolution of acquisition modalities are constantly increasing the fields of application of computer assisted techniques for vascular modeling and a lot of Computer Vision and Computer Graphics research groups are currently active in the field, developing methodologies, algorithms and software prototypes able to recover models of branches of human vascular system from different kinds of input images. Reconstruction methods can be extremely different according to image type, accuracy requirements and level of automation. Some technologies have been validated and are available on medical workstation, others have still to be validated in clinical environments. It is difficult, therefore, to give a complete overview of the different approach used and results obtained, this paper just presents a short review including some examples of the principal reconstruction approaches proposed for vascular reconstruction, showing also the contribution given to the field by the Medical Application Area of CRS4, where methods to recover vascular models have been implemented and used for blood flow analysis, quantitative diagnosis and surgical planning tools based on Virtual Reality
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