
 Greg Bulmash - 2016-07-14 02:13:27 - 
In reply to message 1 from SteveYours is the first question since I posted it. There hasn't been much call to do more with it. So the Lat/Long features never got done. 
Honestly, if I was going to do this as a dynamic deal, I wouldn't bother with server-side processing. Since I wrote this, I spent a few years deep-diving with HTML5. I'd offload the work to the browser with JavaScript and handle it in a canvas element. 
GD is a slow, bothersome library. I had to figure out how to calculate a multiply blend since it doesn't offer it. I'd recommend ImageMagick, but that recently had a big ZeroDay issue. The browser is your best bet.