How can i draw a line graph and output it in format of gif?

I want to design a Active DLL component, which finish the function of drawing line-graph based on the data in database. I hope that the component can process the require and return a gif picture.

You can see the result in this url:
http://202.99.6.52/cgi-bin/KXStockLi...n=KDJ&per=week

I also want this effect.
Can you help me?
Thanks very much!

Well, writing to GIF files is probably going to cost you some, since the GIF format is licensed or something...

The rest is just simply getting data and drawing some colored lines according to that data.