title: Transform quadrilateral into a rectangle?
body: <p>I have scene composed of one arbitrary quadrilateral. I need to be able to transform that quadrilateral into a rect. Each quad is in 2d coordinates, so they have 4 vertex <code>(x_i, y_i)</code>.</p>
  
  <p>The transformation need to have an inverse because the idea is to go back to the original quad after manipulating the rectangle.</p>
  
  <p>What would be the easiest way to perform this operation ? I've heard it's called a perspective transformation, but I've found some small clues that lead me to think this could be quite easy to do.</p>