Best approach to make a selection in an image then creating a mask out of it

Hi All,

I've recently started learning C++ and QT. I'm working on a small project which i have to finish in a couple of weeks. the idea is to create a user interface to load an image then allow the user to make a selection on top of that image (like in the attachments) then when the selection is complete a user clicks a button to generate the mask. The selection could be made as points on the x & y of the mouse position or the image could be loaded with a predefined points with connecting lines between them (i saw something similar) then the suer can increase or decrease the number of points. the image and the created mask will be then passed to Matlab executable file that process the images.

any help, discussion or explanations is appreciated.

All the best.