asp.net实现简单数字验证码实例

using System;

using System.Collections;

using System.Configuration;

using System.Data;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.HtmlControls;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using System.Drawing;

using System.Drawing.Imaging;

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

{

    private int codeLen = 5;//随机显示字符个数

    private int fineness = 100;//图片清晰度

    private int imgWidth = 65;//图片宽度

    private int imgHeight = 20;//图片高度

    private string fontFamily = "Roman";//字体名称

    private int fontSize = 12; //字体大小

    private Random random = new Random();

    protected void Page_Load(object sender, EventArgs e)

    {

        string validateCode = CreateValidateCode();

        Session["RandomNumber"] = validateCode;

        Bitmap bitmap = new Bitmap(imgWidth, imgHeight);

        DisturbBitmap(bitmap);

        DrawValidateCode(bitmap, validateCode);

        bitmap.Save(Response.OutputStream, ImageFormat.Gif);

    }

    private string CreateValidateCode()//得到随机数

    {

        string validateCode = "";

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

        {

            int n = random.Next(10);//返回一个小于最大值得随机数

            validateCode += n.ToString();

        }

        return validateCode;

    }

    private void DisturbBitmap(Bitmap bitmap)//获取背景图

    {

        for (int i = 0; i < bitmap.Width; i++)

        {

            for (int j = 0; j < bitmap.Height; j++)

            {

                if (random.Next(90) <= this.fineness)

                {

                    bitmap.SetPixel(i, j, Color.White);//获取指定位置的像素颜色

                }

            }

        }

    }

    private void DrawValidateCode(Bitmap bitmap, string validateCode)

    {

        Graphics g = Graphics.FromImage(bitmap);

        Font font = new Font(fontFamily, fontSize, FontStyle.Bold);

        g.DrawString(validateCode, font, Brushes.Green, random.Next(-3, 11), random.Next(-4, 1));//在指定区域绘制文本字符

    }

}