C#生成验证码

public static bool GenRad(string strRadnum,System.IO.Stream oOutStream,int nWidth,int nHeight)
{
System.Drawing.Bitmap oImage;

try
{
oImage=new System.Drawing.Bitmap(nWidth,nHeight);


}
catch(System.Exception Dr_ERr)
{
CardSale.Tools.ErrorLog.WriteLog("Photo/GenRad(string strRadnum,System.IO.Stream oOutStream,int nWidth,int nHeight)",Dr_ERr.Message);
return false;
}

System.Drawing.Graphics oGr=System.Drawing .Graphics.FromImage(oImage);
System.Drawing.SolidBrush oBack=new System.Drawing.SolidBrush(System.Drawing.Color.FromArgb(255,255,255));
oGr.FillRectangle(oBack,0,0,nWidth,nHeight);
System.Drawing.Pen oPen=new System.Drawing.Pen(System.Drawing.Color.Black);
System.Drawing.Font oFont=new System.Drawing.Font(System.Drawing.FontFamily.GenericSansSerif,12);
System.Drawing.SolidBrush oLine=new System.Drawing.SolidBrush(System.Drawing.Color.FromArgb(0,0,0));
System.Drawing.Imaging.ImageAttributes imageAttr = new System.Drawing.Imaging.ImageAttributes();
imageAttr.SetGamma(0.1F);

oGr.DrawString(strRadnum,oFont,oLine,5,0);
try
{
oImage.Save(oOutStream,System.Drawing.Imaging.ImageFormat.Jpeg);
}
catch
{
oGr.Dispose();
oImage.Dispose();
return false;
}
oGr.Dispose();
oImage.Dispose();
return true;
}