Snakes, Shapes, and Gradient vector flow

Active contours, or snakes, are computer-generated curves that move within images to find object boundaries. Its 3D version is often known as deformable models or active surfaces in literature. We have developed a new kind of snake that permits the snake to start far from the object, and yet still draws it towards the object, and forces it into boundary concavities. The new snake is based on a new type of external force field, called gradient vector flow, or GVF. This field is computed as a spatial diffusion of the gradient of an edge map derived from the image. This computation causes diffuse forces to exist far from the object, and crisp force vectors near the edges. Combining these forces with the usual internal forces yields a powerful computational object: the GVF snake (2D), or the GVF deformable model (N-D). We have experimented with GVF on line drawings and grayscale images, including images of the heart and brain. Several examples are shown below and both publications an...

• Authors: Chenyang Xu, Jerry L. Prince
• Keywords: Active Contour, Deformable Model, Gradient Vector Flow, Image Segmentation