Need exact co-ordinate points for an irregular shape

I need to calculate slopes of some irregular ROIs. So, I need the exact co-ordinates of few points. Is it possible to get the exact co-ordinate points of the highlighted points? As I have many ROIs in a single image, I need the co-ordinates automatically.

Answer 1

[KSSV]

If I is your binarized image.

[y,x] = find(I) ; 
idx = boundary(x,y) ; 
x = x(idx) ; y = y(idx) ; 

The above gives the coordinates of boundary. You can pick the points based on distance from mean logic.

[Sunetra Banerjee]

Thanks a lot. Now I am able to get the boundary co-ordinates. But, according to this image, I have three ROIs and three centres. How to sort the co-ordinate points according to three other ROIs, to be very specific how to understand till which point it belong to one ROI and then move to the next, so that I can calculate the distances from centres? I am able to sort them but unable to differentiate them in three different groups.

Thanks again.