title: Convert point from coordinate system (0,800) to coordinate system (50,-50) jFrame<->opengl
body: <p>I have a point in the following coordinate system:</p>
  
  <p>Java AWT:</p>
  
  <pre><code>0,0|------------------------|
     |                        |
     |  (middle p. 400,300)   |
     |                        |
     |------------------------|800,600
  </code></pre>
  
  <p>and I want to convert it to the following system:</p>
  
  <p>OpenGL</p>
  
  <pre><code>  50,50|------------------------|
         |                        |
         |     (middle p. 0,0)    |
         |                        |
         |------------------------|-50,-50
  </code></pre>
  
  <p>Any idea how can I do it?</p>