[Plugin: NextGEN Gallery] Slideshow Widget: : Grab single image using PHP

I’m playing around with nextgen to try to get a particular photo from my galleries using a php call.

I used nggDisplayRandomImages to get a random image, however, I would like to get a precise image, e.g. number 4. How do I do that?

I was trying to work out what the code does, especially the ngg_widget_output function in widgets.php, but it’s beyond my level of coding.

Any suggestions would be helpful!
Thanks