ASP.NET实现验证码（加“看不清,换一张”）

/**/////////////////////////////////////////////////////在image.aspx.cs中的代码




using System;


using System.Data;


using System.Configuration;


using System.Collections;


using System.Web;


using System.Web.Security;


using System.Web.UI;


using System.Web.UI.WebControls;


using System.Web.UI.WebControls.WebParts;


using System.Web.UI.HtmlControls;


using System.Drawing;


using System.IO;




public partial class createImg : System.Web.UI.Page




...{


Random ran = new Random();


protected void Page_Load(object sender, EventArgs e)




...{


string str = getRandomValidate(4);


Session["check"] = str; //这一步是为了将验证码写入Session，进行验证，不能缺省，也可一使用cookie


getImageValidate(str);


}


//得到随机字符串,长度自己定义


private string getRandomValidate(int len)




...{


int num;


int tem;


string rtuStr = "";


for (int i = 0; i < len; i++)




...{


num = ran.Next();




/**//*


* 这里可以选择生成字符和数字组合的验证码


*/


//if (i % 2 == 1)


// tem = num % 10 + '0';//生成数字


//else


tem = num % 26 + 'A';//生成字符


rtuStr += Convert.ToChar(tem).ToString();


}


return rtuStr;


}


//生成图像


private void getImageValidate(string strValue)




...{


//string str = "OO00"; //前两个为字母O，后两个为数字0


int width = Convert.ToInt32(strValue.Length * 15); //计算图像宽度


Bitmap img = new Bitmap(width, 23);


Graphics gfc = Graphics.FromImage(img); //产生Graphics对象，进行画图


gfc.Clear(Color.White);


drawLine(gfc, img);


//写验证码，需要定义Font


Font font = new Font("arial", 12, FontStyle.Bold);


System.Drawing.Drawing2D.LinearGradientBrush brush =


new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, img.Width, img.Height), Color.DarkOrchid, Color.Blue, 1.5f, true);


gfc.DrawString(strValue, font, brush, 3, 2);


drawPoint(img);


gfc.DrawRectangle(new Pen(Color.DarkBlue), 0, 0, img.Width - 1, img.Height - 1);


//将图像添加到页面


MemoryStream ms = new MemoryStream();


img.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);


//更改Http头


Response.ClearContent();


Response.ContentType = "image/gif";


Response.BinaryWrite(ms.ToArray());


//Dispose


gfc.Dispose();


img.Dispose();


Response.End();


}


private void drawLine(Graphics gfc, Bitmap img)




...{


//选择画10条线,也可以增加，也可以不要线，只要随机杂点即可


for (int i = 0; i < 10; i++)




...{


int x1 = ran.Next(img.Width);


int y1 = ran.Next(img.Height);


int x2 = ran.Next(img.Width);


int y2 = ran.Next(img.Height);


gfc.DrawLine(new Pen(Color.RosyBrown), x1, y1, x2, y2); //注意画笔一定要浅颜色，否则验证码看不清楚


}


}


private void drawPoint(Bitmap img)




...{




/**//*


//选择画100个点,可以根据实际情况改变


for (int i = 0; i < 100; i++)


{


int x = ran.Next(img.Width);


int y = ran.Next(img.Height);


img.SetPixel(x,y,Color.FromArgb(ran.Next()));//杂点颜色随机


}


*/


int col = ran.Next();//在一次的图片中杂店颜色相同


for (int i = 0; i < 100; i++)




...{


int x = ran.Next(img.Width);


int y = ran.Next(img.Height);


img.SetPixel(x, y, Color.FromArgb(col));


}


}




}








/**/////////////////////////////////////////////////////////////////在页面中的代码




<script language="javascript">


function change()




...{


var img =document.getElementById("Image1");


img.src=img.src+'?';


}


</script>




<img id="Image1" src="Image.aspx"><a href="javascript:change();">看不清,换一张</a>