图像处理水平集的方法介绍1概要.ppt

Active Contours, Level Sets, and Image Segmentation Chunming li Institute of Imaging Scienc Vanderbilt University Url:www.vuiis.vanderbiltedu/-licm E-mail: chunming.li@vanderbilt. edu  Outline Curve evolution and level set methods Curve Evolution from snake to general curve evolution Level Set Methods: basic concepts and methods 2. Numerical issues Difference scheme: upwind scheme, ENO interpolation Reinitialization, velocity extension 3. Introduction to calculus of variations and applications Segmentation variational level set, shape prior Denoising: diffusion, TV  2D Level set dick to play the move dick to play the movie A Movie of chunming  3D Level set dick to play the mowe dick to play the move by Chunmei  More applications of Level Sets 1. Fluid Dynamics 2. Computer Graphics: Surface Rendering, Animation 3. Material Science 4. Others 5  Advantages of Active Contours and Level sets 1. Nice representation of object boun Smooth and closed, good for shape analysis and recognition and oTher applIcaTions 2.5ub-pi× kel accuracy 3. Can incorporate various information such as shape prior and motion 4. Mature mathematical tools can be used calculus of variations PDE, differential geometry  Snake Models  Image Segmentation: Classic Methods An image of blood vessel Thresholding Edge detection  Parametric Active Contours(Kass et al 1987) For a contour C(s)=[(s),y(s), define energy E=/ 2(a C(S)+BC(s)2)ds+ Eat(c(s)ds Eext(z, y)=-v(Ga+I(z,)2  Evolution of Active contours st descent a C(s, t)=ac(s, t)-BC(s, t)i-VEext C(s, 0)=Co(s) Internal force: Regularizes the contour External force: Drives the contour towards the desired In the classic snake model, the external force field is-vf(, y)