Here is an example of converting a Tif to Gif.
Bitmap test = new Bitmap(Iurl);//file path;
Response.ContentType="image/Gif";
System.Guid [] sg = test.FrameDimensionsList;
int FrameCount = test.GetFrameCount(new System.Drawing.Imaging.FrameDimension(sg[0]));
//Decide which frame you want 0 based;
int FrameIndex = 0;//Your choice;
test.SelectActiveFrame(new System.Drawing.Imaging.FrameDimension(sg[0]),FrameIndex);
test.Save(Response.OutputStream,System.Drawing.Imaging.ImageFormat.Gif);
test.Dispose();
//I have dumped the output to a stream and set the contenttype to the image/gif property. Most browsers will render the image;
As for text at the bottom you will have to use an Image class object (rectangle with text) and overlay it.
check the System.Drawing namespace for stuff.
check this site for the namespace info