title: save image to a png file using processing.js
body: <p>I have an small drawing application made in processing.js. I would like to save the image made using the application to a server using a php file (no problem on this).
  I know the canvas element has a method to get that content, canvas.toDataURL() but I dont know how to do the same with processing.js </p>
  
  <p>Any hint? </p>
  
  <p>Cheers! </p>