title: How to get pixel values inside of a rectangle within an image
body: <p>I have an image, where four corner points are defined. Now I want to get the pixel values of the region, that is defined by the 4 corners. Problem is, although it is a rectangle, it has a "slope", which means neither the two upper corner points nor the lower one are at the same height. How can I still solve this issue?</p>
  
  <p>I have not found anything for this yet.. I'd appreciate any kind of support! :)</p>