title: Save openGL output using DevIL or SOIL
body: <p>I have tried using both soil and devil image libraries but the screenshots created are completely black images. For devil I used the function found here <a href="https://stackoverflow.com/questions/13516424/take-screenshot-with-opengl-and-save-it-as-png/17356836#17356836">Take screenshot with openGL and save it as png</a> but the image is still black screen.</p>
  
  <p>Any ideas about saving screenshot or exporting opengl output?</p>