生成图像的页面

在生成图像的页面的pageload事件中写如下代码：

//先生成一个随机数，存在checkCode   中，然后
if(checkCode   ==   null   ||   checkCode.Trim()   ==   String.Empty)
return;

System.Drawing.Bitmap   image   =   new  
System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length   *   12.5)),   20);

Graphics   g   =   Graphics.FromImage(image);

try
{
//生成随机生成器
Random   random   =   new   Random();

//清空图片背景色
g.Clear(Color.White);

// 画图片的背景噪音线
for(int   i=0;   i <25;   i++)
{
int   x1   =   random.Next(image.Width);
int   x2   =   random.Next(image.Width);
int   y1   =   random.Next(image.Height);
int   y2   =   random.Next(image.Height);

g.DrawLine(new   Pen(Color.Silver),   x1,   y1,   x2,   y2);
}

Font   font   =   new   System.Drawing.Font( "Arial ",   12,  
(System.Drawing.FontStyle.Bold   |   System.Drawing.FontStyle.Italic));
System.Drawing.Drawing2D.LinearGradientBrush   brush   =   new  
System.Drawing.Drawing2D.LinearGradientBrush(new   Rectangle(0,   0,  
image.Width,   image.Height),   Color.Black,   Color.Black,   1.2f,   true);
g.DrawString(checkCode,   font,   brush,   2,   2);

//画图片的前景噪音点

for(int   i=0;   i <100;   i++)
{
int   x   =   random.Next(image.Width);
int   y   =   random.Next(image.Height);

image.SetPixel(x,   y,   Color.FromArgb(random.Next()));
}

//画图片的边框线
g.DrawRectangle(new   Pen(Color.Silver),   0,   0,   image.Width   -   1,   image.Height   -   1);

System.IO.MemoryStream   ms   =   new   System.IO.MemoryStream();
image.Save(ms,   System.Drawing.Imaging.ImageFormat.Gif);
Response.ClearContent();
Response.ContentType   =   "image/Gif ";
Response.BinaryWrite(ms.ToArray());
}
finally
{
g.Dispose();
image.Dispose();
}