验证码生成源码

1.首先生成不重复的字符串，以下是主要代码：

                                                  int rep = 0;

            string str = string .Empty;

            long num2 = DateTime .Now.Ticks + rep;

            rep++;

            Random random = new Random(((int )(((ulong)num2) & 0xffffffffL)) | (( int)(num2 >> rep)));

            for (int i = 0; i < 4; i++)

            {

                char ch;

                int num = random.Next();

                if ((num % 2) == 0)

                {

                    ch = ( char)(0x30 + ((ushort )(num % 10)));

                }

                else

                {

                    ch = ( char)(0x41 + ((ushort )(num % 0x1a)));

                }

                str = str + ch.ToString();

            }

            Code = str;

该算法会生成0，o,1,i等容易混淆的字符，后期我们会稍作调整。

2.生成字符过后，我们需要把字符生成图片。

int randAngle = 45;            //随机转动角度

            int mapwidth = (int )(Code.Length * 22);

            Bitmap map = new Bitmap(mapwidth, 28);                            //创建图片背景

            Graphics graph = Graphics .FromImage(map);

            graph.Clear( Color.AliceBlue);              //清除画面，填充背景

            Random rand = new Random();

            //验证码旋转，防止机器识别

            char[] chars = Code.ToCharArray();            //拆散字符串成单字符数组

            //文字距中

            StringFormat format = new StringFormat (StringFormatFlags.NoClip);

            format.Alignment = StringAlignment.Center;

            format.LineAlignment = StringAlignment .Center;

            ////再画一条曲线连接所有字符

            double x1 = 10;

            double y1 = 0;

            for (double x = 1; x < 720; x++)

            {

                Pen pen = new Pen( Color.Blue, rand.Next(3));

                //SIN最大值为1,而我图上用了 100像素, 所以有

                //100/1=100  故而y 要乘100;

                // x/180*Math.PI 这个表达式把角度换成弧度值

                double y = Math .Sin(x / 180 * Math.PI) * 28;

                //SIN值一个循环为360度，而我图上用了 200像素表示，所以有：

                //360/200=1.8 故而x 值要除1.8

                graph.DrawLine(pen, ( float)x1, (float )y1 + 1, (float )(x) + 1, (float)y + 1);

                x1 = x + 1;

                y1 = y;

            }

            string[] fontArray = { "Verdana" , "Microsoft Sans Serif", "Comic Sans MS" , "Arial", "宋体" };

            for (int i = 0; i < chars.Length; i++)

            {

                Font fontstyle = new Font(fontArray[rand.Next(5)], rand.Next(20, 22), FontStyle.Regular);            //字体样式

                Point dot = new Point(rand.Next(14, 16), 16);

                //graph.DrawString(dot.X.ToString(),  fontstyle,  new  SolidBrush(Color.Black),  10,  150);                //测试X坐标显示间距的

                float angle = rand.Next(-randAngle, randAngle);            //转动的度数

                graph.TranslateTransform(dot.X, dot.Y);          //移动光标到指定位置

                graph.RotateTransform(angle);

                graph.DrawString(chars[i].ToString(), fontstyle, new SolidBrush( Color.Blue), 1, 1, format);

                graph.RotateTransform(-angle);                    //转回去

                graph.TranslateTransform(2, -dot.Y);          //移动光标到指定位置

            }

            //生成图片

            System.IO. MemoryStream ms = new System.IO.MemoryStream ();

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

            CodeMap = new Bitmap (map);

            graph.Dispose();

            map.Dispose();

详解地址:http://www.517up.com/chat/%E4%BB%8E%E9%AA%8C%E8%AF%81%E7%A0%81%E8%AF%B4%E8%B5%B7?postbadges=true