title: how to fill inside a boundary trace?
body: <p>I have a mask of image and I have defined a boundary on this image as bellow:</p>
  
  <p><img src="https://i.stack.imgur.com/mGD9D.jpg" alt="im1">  </p>
  
  <p>now I want to remove the pixels out of that boundary and get a mask like this:</p>
  
  <p><img src="https://i.stack.imgur.com/nq261.jpg" alt="im2">  </p>
  
  <p>the boundary is a matrix of 70*2. 
  and the image is 4000*3000 in size. </p>
  
  <p>I can not use <code>imfill</code> in matlab as my boundary is discrete!<br>
  Do you know how I can do it in MATLAB?</p>