converting jpeg image into gif

Question

hi all , i am new to graphics programming and dont have any senior graphics programmer who will guide me..........Actually i got stuck with problem ie when i convert gif to jpeg it it works.......but when i convert jpeg to gif then it introduces noise.....image quality get degraded .... here i am providing with code snipet ...

Bitmap newbit = new Bitmap(Server.MapPath("./images/CAS1.Jpg"));

Graphics g1 = Graphics.FromImage(newbit);

Response.ContentType = "image/gif";

newbit.Save(Server.MapPath("./images/CAS2.gif"));, ImageFormat.gif);




Can i improve this process by using others functions provided in GDI +

Any Quick help would be deeply needed and appreciated….