We found a solution to get JPGs / Gifs / PNGs / Tiffs
We use a Microsoft Windows Server and bought "HTML Snapshot ActiveX Component"
from http://www.guangmingsoft.net/htmlsnapshot/help.htm (180$)
This component makes a Snapshot from a Webpage, using a given URL (URLs of the Charts).
We test it since yesterday and it works fine and without any problems.
They also deliver code examples for different Languages like, ASP, ASP.net, Coldfusion, Python...
For Unix and Linux Users it might help to search for simalar tools (url to image).
Best regards
Kersten