Discrete bisector function and Euclidean skeleton in 2D and 3D

International audienceWe propose a new definition and an exact algorithm for the discrete bisector function, which is an important tool for analyzing and filtering Euclidean skeletons. We also introduce a new thinning algorithm which produces homotopic discrete Euclidean skeletons. These algorithms, which are valid both in 2D and 3D, are integrated in a skeletonization method which is based on exact transformations, allows the filtering of skeletons, and is computationally efficient

Moving-edge detection via heat flow analogy

In this paper, a new and automatic moving-edge detection algorithm is proposed, based on using the heat flow analogy. This algorithm starts with anisotropic heat diffusion in the spatial domain, to remove noise and sharpen region boundaries for the purpose of obtaining high quality edge data. Then, isotropic and linear heat diffusion is applied in the temporal domain to calculate the total amount of heat flow. The moving-edges are represented as the total amount of heat flow out from the reference frame. The overall process is completed by non-maxima suppression and hysteresis thresholding to obtain binary moving edges. Evaluation, on a variety of data, indicates that this approach can handle noise in the temporal domain because of the averaging inherent of isotropic heat flow. Results also show that this technique can detect moving-edges in image sequences, without background image subtraction

Evaluations of Thinning Algorithms for Preprocessing of Handwritten Characters

Thinning algorithms have played an important role in preprocessing phase which decides the success of recognition in the OCR system. This paper report on the performance of 11 thinning algorithms from the perspective of character recognition where different aspects of the performance of each algorithm like computing time, deviation from perfect 8-connectedness, and number of possible noise spurs present in the skeletons are considered

A Parallel Thinning Algorithm for Grayscale Images

International audienceGrayscale skeletonization offers an interesting alternative to traditional skeletonization following a binarization. It is well known that parallel algorithms for skeletonization outperform sequential ones in terms of quality of results, yet no general and well defined framework has been proposed until now for parallel grayscale thinning. We introduce in this paper a parallel thinning algorithm for grayscale images, and prove its topological soundness based on properties of the critical kernels framework. The algorithm and its proof, given here in the 2D case, are also valid in 3D. Some applications are sketched in conclusion

An automatic correction of Ma's thinning algorithm based on P -simple points

International audienceThe notion of P -simple points has been introduced by Bertrand to conceive parallel thinning algorithms. In 'A 3D fully parallel thinning algorithm for generating medial faces', Ma has proposed an algorithm for which there exists objects whose topology is not preserved. In this paper, we propose a new application of P -simple points: to automatically correct Ma's algorithm

Topological segmentation of discrete surfaces

International audienceThis article proposes a new approach to segment a discrete 3-D object into a structure of characteristic topological primitives with attached qualitative features. This structure can be seen itself as a qualitative description of the object, because : - it is intrinsic to the 3-D object, which means it is stable to rigid transformations (rotations and translations); - it is locally defined, and therefore stable to partial occlusions and local modifications of the object structure; - it is robust to noise and small deformations, as confirmed by our experimental results. Our approach concentrates on topological properties of discrete surfaces. These surfaces may correspond to the external surface of the objects extracted by a 3-D edge detector, or to the skeleton surface obtained by a new thinning algorithm. Our labeling algorithm is based on very local computations, allowing massively parallel computations and real-time computations. An indirect result of these topological properties is a new characterization of simple points. We present a realistic experiment to characterize and locate spatially a complex 3-D medical object using the proposed segmentation of its skeleton

A Thinning Algorithm Based on Directional Distance Transformations

A new thinning algorithm is presented in this paper，which is based on directional distance transformations. The transformations in a pair of opposite directions are applied separately for horizontal and vertical line segments. The algorithm has only two raster scans of images to get the final skeleton images，although the conventional thinning methods have more than four raster scans. In the first scan the distance transformations are addressed to all the l-pixels，and the O-pixels above the outlines of 1-pixels which are used to classify the line segments as horizontal or non-horizontal ones. In the second scan the skeleton pixels are fixed to form the connected paths. The experiments for various kinds of sample images show that the algorithm produces the skeletons with no shrink in length at the ends of lines and with minimum distortions near the intersections or the contacts of line images