title: How to combine multiple PNGs into one big PNG file?
body: <p>I have approx. 6000 PNG files (256*256 pixels) and want to combine them into a big PNG holding all of them programmatically.</p>
  
  <p>What's the best/fastest way to do that?</p>
  
  <p>(The purpose is printing on paper, so using some web-technology is not an option and having one, single picture file will eliminate many usage errors.)</p>
  
  <p>I tried fahd's suggestion but I get a <code>NullPointerException</code> when I try to create a <code>BufferedImage</code> with 24576 pixels wide and 15360 pixels high. Any ideas?</p>