How to generate GIF with transparent background?

Question

C++ / C#

Hello.
Actually, it is necessary to generate GIF animation on a transparent background. I have a set of frames that are saved as avi , then the video is converted to GIF using ffmpeg . I can fill the background of the original frames with any color.
Question: is it possible to fill the background with some color so that the background becomes transparent during conversion? Or can you recommend a lightweight C or C++ library for working with GIFs that I could use to directly generate GIFs from existing frames (and adjust the transparency of course).
Thanks in advance.
PS:
Tried using libgd, but I'm using Visual Studio 2008 and the manual says you can use Visual Studio 2006 or earlier.
Addition:
I was able to run libgd , but I didn't get transparency. Please, who worked with gif or with libgd , help with advice!