Constrained Active Contour For Interactive Image Segmentation
نویسندگان
چکیده
Interactive image segmentation algortihms incorporates small amount of user interaction to define the desired content to be extracted, has received much attention in the recent years. We propose a robust and accurate interactive method based on the recently developed continuous-domain convex active contour model. The proposed method exhibits many desirable properties of an effective interactive image segmentation algorithm, including robustness to user inputs and different initializations with an efficient and light-weight solution for rendering smooth shadow boundaries that do not reveal the tessellation of the shadowcasting geometry. Our algorithm reconstructs the smooth contours of the underlying mesh and then extrudes shadow volumes from the smooth silhouettes to render the shadows. For this purpose we propose an improved silhouette reconstruction using the vertex normal of the underlying smooth mesh. Then our method subdivides the silhouette loops until the contours are sufficiently smooth and project to smooth shadow boundaries. Here we solve the two problems in a unified framework. Gradient controlled partial differential equation (PDE) surfaces to express terrain surfaces, in which the surface shapes can be globally determined by the contours, their locations, and height and gradient values. The surface generated by this method is accurate in the sense of exactly coinciding with the original contours and smooth with C1 (contour active convex region) continuity everywhere. The method can reveal smooth saddle shapes caused by surface branching of one to more and can make rational interpolated subcontours between two or more neighbouring
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