Physical Modeling Techniques in Active Contours for Image Segmentation
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Physical modeling method, represented by simulation and visualization of the principles in physics, is introduced in the shape extraction of the active contours. The objectives of adopting this concept are to address the several major difficulties in the application of Active Contours. Primarily, a technique is developed to realize the topological changes of Parametric Active Contours (Snakes). The key strategy is to imitate the process of a balloon expanding and filling in a closed space with several objects. After removing the touched balloon surfaces, the objects can be identified by surrounded remaining balloon surfaces. A burned region swept by Snakes is utilized to trace the contour and to give a criterion for stopping the movement of Snake curve. When the Snakes terminates evolution totally, through ignoring this criterion, it can form a connected area by evolving the Snakes again and continuing the region burning. The contours extracted from the boundaries of the burned area can represent the child snake of each object respectively. Secondly, a novel scheme is designed to solve the problems of leakage of the contour from the large gaps, and the segmentation error in Geometric Active Contours (GAC). It divides the segmentation procedure into two processing stages. By simulating the wave propagating in the isotropic substance at the final stage, it can significantly enhance the effect of image force in GAC based on Level Set and give the satisfied solutions to the two problems. Thirdly, to support the physical models for active contours above, we introduce a general image force field created on a template plane over the image plane. This force is more adaptable to noisy images with complicated geometric shapes.
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