首先，项目添加对ZKWeb.System.Drawing的引用；
生成验证码代码如下：
public class VierificationCodeServices { /// <summary> /// 该方法用于生成指定位数的随机数 /// </summary> /// <param name="VcodeNum">参数是随机数的位数</param> /// <returns>返回一个随机数字符串</returns> private string RndNum(int VcodeNum) { //验证码可以显示的字符集合 string vChar = "0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f,g,h,i,j,k,l,m,n,p,q,r,s,t,u,v,w,x,y,z,A,B,C,D,E,F,G,H,I,J,K,L,M,N,P,P,Q,R,S,T,U,V,W,X,Y,Z"; string[] vcArray = vChar.Split(new Char[] { ',' });//拆分成数组 string code = "";//产生的随机数 int temp = -1;//记录上次随机数值，尽量避避免生产几个一样的随机数 Random rand = new Random(); //采用一个简单的算法以保证生成随机数的不同 for (int i = 1; i < VcodeNum + 1; i++) { if (temp != -1) { rand = new Random(i * temp * unchecked((int)DateTime.Now.Ticks));//初始化随机类 } int t = rand.Next(61);//获取随机数 if (temp != -1 && temp == t) { return RndNum(VcodeNum);//如果获取的随机数重复，则递归调用 } temp = t;//把本次产生的随机数记录起来 code += vcArray[t];//随机数的位数加一 } return code; } /// <summary> /// 该方法是将生成的随机数写入图像文件 /// </summary> /// <param name="code">code是一个随机数</param> /// <param name="numbers">生成位数（默认4位）</param> public MemoryStream Create(out string code, int numbers = 4) { code = RndNum(numbers); Bitmap img = null; Graphics g = null; MemoryStream ms = null; Random random = new Random(); //验证码颜色集合 Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple }; //验证码字体集合 string[] fonts = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" }; //定义图像的大小，生成图像的实例 img = new Bitmap((int)code.Length * 18, 32); g = Graphics.FromImage(img);//从Img对象生成新的Graphics对象 g.Clear(Color.White);//背景设为白色 //在随机位置画背景点 for (int i = 0; i < 100; i++) { int x = random.Next(img.Width); int y = random.Next(img.Height); g.DrawRectangle(new Pen(Color.LightGray, 0), x, y, 1, 1); } //验证码绘制在g中 for (int i = 0; i < code.Length; i++) { int cindex = random.Next(7);//随机颜色索引值 int findex = random.Next(5);//随机字体索引值 Font f = new Font(fonts[findex], 15, FontStyle.Bold);//字体 Brush b = new SolidBrush(c[cindex]);//颜色 int ii = 4; if ((i + 1) % 2 == 0)//控制验证码不在同一高度 { ii = 2; } g.DrawString(code.Substring(i, 1), f, b, 3 + (i * 12), ii);//绘制一个验证字符 } ms = new MemoryStream();//生成内存流对象 img.Save(ms, ImageFormat.Jpeg);//将此图像以Png图像文件的格式保存到流中 //回收资源 g.Dispose(); img.Dispose(); return ms; } }
发布到CentOS中，需要安装libgdiplus：
yum install autoconf automake libtool yum install freetype-devel fontconfig libXft-devel yum install libjpeg-turbo-devel libpng-devel giflib-devel libtiff-devel libexif-devel yum install glib2-devel cairo-devel git clone https://github.com/mono/libgdiplus cd libgdiplus ./autogen.sh make make install cd /usr/lib64/ ln -s /usr/local/lib/libgdiplus.so gdiplus.dll
也可以这样安装：
yum install -y epel-release yum whatprovides libgdiplus yum install -y libgdiplus-2.10-9.el7.x86_64 yum install -y dejavu-fonts-common dejavu-lgc-sans-mono-fonts