NGVF: An improved external force field for active contour model

An improved external force field for active contour model, called as NGVF, is presented in this paper. Based on analyzing the diffusion process of the GVF and three interpolation functions, it is found that the generation of GVF contains diffusions in two orthogonal directions along the edge of image, one is the tangent direction and the other is the normal direction. Moreover, the diffusion in the normal direction plays the key role on the diffusion of GVF, while the diffusion in the tangent direction has little effect. So the GVF in the normal direction (NGVF) is taken as a new force field to study. Experiment results with several test images reveal that, compared with GVF, NGVF can enter into long, thin indention and has faster convergence speed towards the concavity and bigger time step.