车神

图片验证码类:

using System;
using System.IO;
using System.Drawing;
using System.Drawing.Imaging;

namespace Lover_Data.Util
{
    /**//// <summary>
    /// ValidateImage 的摘要说明。
    /// </summary>
    public class ValidateImage
    {
        public ValidateImage()
        {
            //
            // TODO: 在此处添加构造函数逻辑
            //
        }

        /**//// <summary>
        /// 获得生成的图片的MemoryStream
        /// </summary>
        /// <param name="nLen">验证码长度</param>
        /// <param name="strKey">输出参数，验证码的内容</param>
        /// <returns>返回要输出到浏览器的流</returns>
        public MemoryStream GenerateVerifyImage(int nLen,out string strKey)
        {
            int nBmpWidth = 13*nLen+5;
            int nBmpHeight = 25;
            System.Drawing.Bitmap bmp = new System.Drawing.Bitmap(nBmpWidth,nBmpHeight);

            // 1. 生成随机背景颜色
            int nRed,nGreen,nBlue;  // 背景的三元色
            System.Random rd = new Random((int)System.DateTime.Now.Ticks);
            nRed = rd.Next(255)%128+128;
            nGreen = rd.Next(255)%128+128;
            nBlue = rd.Next(255)%128+128;

            // 2. 填充位图背景
            System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(bmp);
            graph.FillRectangle(new SolidBrush(System.Drawing.Color.FromArgb(nRed,nGreen,nBlue)),0,0,nBmpWidth,nBmpHeight);

            // 3. 绘制干扰线条，采用比背景略深一些的颜色
            int nLines = 3;
            System.Drawing.Pen pen = new System.Drawing.Pen(System.Drawing.Color.FromArgb(nRed-17,nGreen-17,nBlue-17),2);
            for(int a =0;a< nLines;a++)
            {
                int x1 = rd.Next() % nBmpWidth;
                int y1 = rd.Next() % nBmpHeight;
                int x2 = rd.Next() % nBmpWidth;
                int y2 = rd.Next() % nBmpHeight;
                graph.DrawLine(pen,x1,y1,x2,y2);
            }

            // 采用的字符集，可以随即拓展，并可以控制字符出现的几率
            string strCode = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";

            strKey = "";
            // 4. 循环取得字符，并绘制
            for(int i=0;i < nLen;i++)
            {
                int x = (i*13 + rd.Next(3));
                int y = rd.Next(4) + 1;

                // 确定字体
                System.Drawing.Font font = new System.Drawing.Font("Courier New",12 + rd.Next()%4,System.Drawing.FontStyle.Bold);
                char c = strCode[rd.Next(strCode.Length)];  // 随机获取字符
                strKey += c.ToString();

                // 绘制字符
                graph.DrawString(c.ToString(),font,new SolidBrush(System.Drawing.Color.FromArgb(nRed-60+y*3,nGreen-60+y*3,nBlue-40+y*3)),x,y);
            }
            
            // 5. 输出流
            System.IO.MemoryStream bstream = new System.IO.MemoryStream();
            bmp.Save(bstream,System.Drawing.Imaging.ImageFormat.Jpeg);
            bmp.Dispose();
            graph.Dispose();
            return bstream;
        }

    }
}

使用:
首先新建一个页面WebForm1.aspx,在Page_Load中加入:

private void Page_Load(object sender, System.EventArgs e)
        {
            ValidateImage vi = new ValidateImage();
            string str;
            MemoryStream ms = vi.GenerateVerifyImage(4,out str);
            Session["Validate"] = str;
            Response.ClearContent();
            Response.ContentType = "images/Jpeg";
            Response.BinaryWrite(ms.ToArray());
            Response.End();
            ms.Close();
        }

然后,在需要图片验证码的页面HTML中放一个img,代码如下:
img参数:id="MzImgExpPwd" src="Util/ShowValidateImage.aspx?temp='+ (new Date().getTime().toString(36)) +'"
更换图片的连接参数:onclick="document.getElementById('MzImgExpPwd').src='Util/ShowValidateImage.aspx?temp='+ (new Date().getTime().toString(36)); return false" href="#"
A onclick="document.getElementById('MzImgExpPwd').src='Util/ShowValidateImage.aspx?temp='+ (new Date().getTime().toString(36)); return false" href="#">换图片