## The Elastica Model for Image Restoration: An Operator-Splitting Approach

Series
Applied and Computational Mathematics Seminar
Time
Friday, February 21, 2020 - 2:00pm for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Roland Glowinski – University of Houston, Hong Kong Baptist University – roland@math.uh.eduhttps://www.math.uh.edu/~roland/
Organizer

The most popular model for Image Denoising is without any doubt the ROF (for Rudin-OsherFatemi) model. However, since the ROF approach has some drawbacks (the stair-case effect being one of them) practitioners have been looking for alternatives. One of them is the Elastica model, relying on the minimization in an appropriate functional space of the energy functional $J$ defined by

$$J(v)=\varepsilon \int_{\Omega} \left[ a+b\left| \nabla\cdot \frac{\nabla v}{|\nabla v|}\right|^2 \right]|\nabla v| d\mathbf{x} + \frac{1}{2}\int_{\Omega} |f-v|^2d\mathbf{x}$$

where in $J(v)$: (i) $\Omega$ is typically a rectangular region of $R^2$ and $d\mathbf{x}=dx_1dx_2$. (ii) $\varepsilon, a$ and $b$ are positive parameters. (iii) function $f$ represents the image one intends to denoise.

Minimizing functional $J$ is a non-smooth, non-convex bi-harmonic problem from Calculus of  Variations. Its numerical solution is a relatively complicated issue. However, one can achieve this task rather easily by combining operator-splitting and finite element approximations. The main goal of this lecture is to describe such a methodology and to present the results of numerical experiments which validate it.