验证码

public class RandomHandler : IHttpHandler,IRequiresSessionState
{
   
    public void ProcessRequest (HttpContext context) {
        context.Response.ContentType = "image/gif";
        Bitmap map = new Bitmap(110,23);
        Graphics g = Graphics.FromImage(map);
        g.Clear(Color.White);

        this.DrawPoint(ref g);
        this.DrawLine( ref g);
       
        Color codeColor=Color.FromArgb(RandomBuilder.Next(0, 255), RandomBuilder.Next(0, 255), RandomBuilder.Next(0, 255));
        string code = RandomBuilder.GetRandomCode(6);
        context.Session["Code"] = code;

        g.DrawString(code,new Font("Arial Black",14),new SolidBrush(codeColor),new PointF(0.0f,0.0f));
        g.Flush();
        g.Dispose();

        map.Save(context.Response.OutputStream,ImageFormat.Jpeg);
        context.Response.End();
        map.Dispose();
    }

    private void DrawPoint(ref Graphics g)
    {
        int pointCount = RandomBuilder.Next(30,70);
       
        for(int i =0;i<pointCount;i++)
        {
            g.DrawRectangle(new Pen(
                new SolidBrush(Color.FromArgb(RandomBuilder.Next(0, 255), RandomBuilder.Next(0, 255), RandomBuilder.Next(0, 255)
                    ))
                ), RandomBuilder.Next(0, 100), RandomBuilder.Next(0, 30)
                ,1,1
                );
            g.Flush();
            continue;
        }
      
    }

    private void DrawLine(ref Graphics g)
    {
        int lineCount = RandomBuilder.Next(1, 10);

        for (int i = 0; i < lineCount; i++)
        {
           
            int x1=RandomBuilder.Next(0,100);
            int x2=RandomBuilder.Next(0,100);
            int y1=RandomBuilder.Next(0,30);
            int y2=RandomBuilder.Next(0,30);
            g.DrawLines(new Pen(
                new SolidBrush(Color.FromArgb(RandomBuilder.Next(0, 255), RandomBuilder.Next(0, 255), RandomBuilder.Next(0, 255)
                    ))
                ),new Point[]{new Point(x1,y1),new Point(x2,y2)}
                );
            g.Flush();
            continue;
        }
    }
 
    public bool IsReusable {
        get {
            return false;
        }
    }

}

调用方法：

<img  id="img" src="RandomHandler.ashx" alt="验证码" onclick="this.src='RandomHandler.ashx?'+Math.random();" />