Inward and outward curve evolution using level set method

Iterative curve evolution techniques are powerful methods for image segmentation. Classical methods proposed curve evolutions which guarantee close contours at convergence and, combined with the level set method, they easily handled curve topology changes. However, these methods allow only one-way curve evolutions: shrinking or growing of the curve. Thus, the initial curve must encircle all the objects to be segmented or several curves must be used, each one totally inside one object. In this paper, we present a new approach of iterative curve evolution using the level set method based on the variational criterion of an inverse problem. Besides the closing of the final contours and the curve topology change management, our method allows a two-way curve evolution: parts of the curve evolve in the outward direction while others evolve in the inward direction. It offers much more freedom in the initial curve position than with a classical geodesic search method. Our algorithm performs accurate and precise segmentations, with length penalty. Results are shown on damaged images with complex objects (including sharp angles, deep concavities or holes).