Auto detect specific region of image

Hello,

I am trying to design a small image repair app in matlab. The flowchart goes like: 1) Program will take some damaged old picture as input 2) Identify the damaged region automatically 3) Fill its image matrix with all zeros (for the damaged region) 4) Apply matrix completion/approximation algorithms (such as SVT or incremental SVD) to approximate the 'zeros' region. 5) Output complete repaired image

I tried doing several things in this attempt, tried to convert input image in binary and imfill methods. tried this demo provided by user: ImageAnalyst: https://in.mathworks.com/matlabcentral/answers/84018-filling-a-specific-region-with-a-colour , but it needs user to interfare for identifying the damaged region. I want it to be automated. I don't know about masking, how does it work? will it solve the problem? how?

Here's the image: