title: Crop an right-angled triangle image in MATLAB
body: <p>I would like to extract a certain region of an image, specifically a triangular part of it. My image is of size <code>444x256x3</code>. The following picture illustrates which part I want to extract:</p>
  
  <p><img src="https://i.stack.imgur.com/kIB1Z.jpg" alt="enter image description here"></p>
  
  <p>I would like to extract the triangle formed by the red dotted line (right-triangle).</p>