Event News

Lecture on Imaging


April 9th (Thursday)
Room 1212 (Lecture room 1), National Institute of Informatics
Professor Raymond H. Chan
Department of Mathematics, The Chinese University of Hong Kong, Shatin, Hong Kong.
A Two-stage Image Segmentation Method using a Convex Variant of the Mumford-Shah Model and Thresholding
The Mumford-Shah model is one of the most important image segmentation models, and has been studied extensively in the last twenty years. In this talk, we propose a two-stage segmentation method based on the Mumford-Shah model.
The first stage of our method is to find a smooth solution $g$ to a convex variant of the Mumford-Shah model. Once $g$ is obtained, then in the second stage, the segmentation is done by thresholding $g$ into different phases. The thresholds can be given by the users or can be obtained automatically using any clustering methods. Because of the convexity of the model, $g$ can be solved efficiently by techniques like the split-Bregman algorithm or the Chambolle-Pock method. We prove that our method is convergent and the solution $g$ is always unique. In our method, there is no need to specify the number of segments $K$ ($K\ge 2$) before finding $g$. We can obtain any $K$-phase segmentations by choosing $(K-1)$ thresholds after $g$ is found in the first stage; and in the second stage there is no need to recompute $g$ if the thresholds are changed to reveal different segmentation features in the image. Experimental results show that our two-stage method performs better than many standard two-phase or multi-phase segmentation methods for very general images, including anti-mass, tubular, MRI, noisy, and blurry images; and for very general noise models such as Gaussian, Poisson and multiplicative Gamma noise. We will also mention the generalization to color images.

Ken Hayami
E-mail: hayami[at]nii.ac.jp
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