[转]C#动态生成文字图片

本文转自：http://hi.baidu.com/lantis214/blog/item/e53c35fe83a950355d60083f.html

原文如下

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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.Drawing.Imaging;
using System.Drawing.Drawing2D;
using System.Collections.Generic;
using System.Text;
public partial class Default2 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        this.CreateCheckCodeImage(GenerateCheckCode());
    }

    private string GenerateCheckCode()
    {
        //int number;
        //char code;
        string checkCode = String.Empty;

        System.Random random = new Random();

        Encoding gb = Encoding.GetEncoding("gb2312");
        //调用函数产生4个随机中文汉字编码
        object[] bytes = CreateRegionCode(6);
        //根据汉字编码的字节数组解码出中文汉字
        string str1 = gb.GetString((byte[])Convert.ChangeType(bytes[0], typeof(byte[])));
        string str2 = gb.GetString((byte[])Convert.ChangeType(bytes[1], typeof(byte[])));
        string str3 = gb.GetString((byte[])Convert.ChangeType(bytes[2], typeof(byte[])));
        string str4 = gb.GetString((byte[])Convert.ChangeType(bytes[3], typeof(byte[])));
        //输出的控制台
        checkCode = str1 + str2 + str3 + str4;
       Response.Cookies.Add(new HttpCookie("ValidCode", checkCode));
        return checkCode;
    }

    #region 产生波形滤镜效果
    private static object[] CreateRegionCode(int strlength)
    {
        //定义一个字符串数组储存汉字编码的组成元素
        string[] rBase = new String[16] { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };
        Random rnd = new Random();
        //定义一个object数组用来
        object[] bytes = new object[strlength];

        /*每循环一次产生一个含两个元素的十六进制字节数组，并将其放入bject数组中
        每个汉字有四个区位码组成
        区位码第1位和区位码第2位作为字节数组第一个元素
        区位码第3位和区位码第4位作为字节数组第二个元素
        */
        for (int i = 0; i < strlength; i++)
        {
            //区位码第1位
            int r1 = rnd.Next(11, 14);
            string str_r1 = rBase[r1].Trim();

            //区位码第2位
            rnd = new Random(r1 * unchecked((int)DateTime.Now.Ticks) + i);//更换随机数发生器的

            //种子避免产生重复值
            int r2;
            if (r1 == 13)
            {
                r2 = rnd.Next(0, 7);
            }
            else
            {
                r2 = rnd.Next(0, 16);
            }
            string str_r2 = rBase[r2].Trim();

            //区位码第3位
            rnd = new Random(r2 * unchecked((int)DateTime.Now.Ticks) + i);
            int r3 = rnd.Next(10, 16);
            string str_r3 = rBase[r3].Trim();

            //区位码第4位
            rnd = new Random(r3 * unchecked((int)DateTime.Now.Ticks) + i);
            int r4;
            if (r3 == 10)
            {
                r4 = rnd.Next(1, 16);
            }
            else if (r3 == 15)
            {
                r4 = rnd.Next(0, 15);
            }
            else
            {
                r4 = rnd.Next(0, 16);
            }
            string str_r4 = rBase[r4].Trim();

            //定义两个字节变量存储产生的随机汉字区位码
            byte byte1 = Convert.ToByte(str_r1 + str_r2, 16);
            byte byte2 = Convert.ToByte(str_r3 + str_r4, 16);
            //将两个字节变量存储在字节数组中
            byte[] str_r = new byte[] { byte1, byte2 };

            //将产生的一个汉字的字节数组放入object数组中
            bytes.SetValue(str_r, i);
        }
        return bytes;
    }

    private const double PI = 3.1415926535897932384626433832795;
    private const double PI2 = 6.283185307179586476925286766559;
    private System.Drawing.Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase)
    {
        System.Drawing.Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height);

        // 将位图背景填充为白色
        System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(destBmp);
        graph.FillRectangle(new SolidBrush(System.Drawing.Color.White), 0, 0, destBmp.Width, destBmp.Height);
        graph.Dispose();

        double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width;

        for (int i = 0; i < destBmp.Width; i++)
        {
            for (int j = 0; j < destBmp.Height; j++)
            {
                double dx = 0;
                dx = bXDir ? (PI2 * (double)j) / dBaseAxisLen : (PI2 * (double)i) / dBaseAxisLen;
                dx += dPhase;
                double dy = Math.Sin(dx);

                // 取得当前点的颜色
                int nOldX = 0, nOldY = 0;
                nOldX = bXDir ? i + (int)(dy * dMultValue) : i;
                nOldY = bXDir ? j : j + (int)(dy * dMultValue);

                System.Drawing.Color color = srcBmp.GetPixel(i, j);
                if (nOldX >= 0 && nOldX < destBmp.Width
                && nOldY >= 0 && nOldY < destBmp.Height)
                {
                    destBmp.SetPixel(nOldX, nOldY, color);
                }
            }
        }
        return destBmp;
    }
    #endregion

    private void CreateCheckCodeImage(string checkCode)
    {
        if (checkCode == null)
            return;

        System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 27.0)), 25);
        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 < 12; 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", 16, (System.Drawing.FontStyle.Bold 　 System.Drawing.FontStyle.Italic));
            Font font = new System.Drawing.Font("楷体_GB2312", 16, (System.Drawing.FontStyle.Bold));
            System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 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()));
            }

            //image = TwistImage(image, true, 3, 1);
            //画图片的波形滤镜效果
            //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();
        }
    }
}