为什么画的图保存为gif格式时,透明像素变成了黑色?

Question

不知有没有办法解决?Bitmap bp=new Bitmap(600,600);
Graphics g=Graphics.FromImage(bp);
FlowGraph.Flow flow=new FlowGraph.Flow();
flow.GraphObject=new ArrayList();
flow.LoadFromFile(Server.MapPath"FlowGraph/12_quexian.graph"));
flow.DrawGraph(g,30);
Response.ContentType="image/gif";
bp.Save(Response.OutputStream,System.Drawing.Imaging.ImageFormat.Gif);

Answer 1

第二行之后加上：
g.Clear(Color.White); // 绘制背景

Answer 2

http://bbs.mscommunity.com/Forums/ShowThread.aspx?PostID=11627