程序代码：

        using System.Drawing;
        using System.Drawing.Drawing2D;

        public static string CreateCode(int codeLength)
        {
            const string codes = "0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f,g,h,j,k,m,n,p,q,r,s,t,u,v,w,x,y,z,A,B,C,D,E,F,G,H,J,K,M,N,P,Q,R,S,T,U,V,W,X,Y,Z";
            var strArr         = codes.Split(',');
            var result         = "";
            var random         = new Random((int) DateTime.Now.Ticks);
            for (var i = 0; i < codeLength; i++)
                result += strArr[random.Next(0, strArr.Length)];
            return result;
        } 

        public static Bitmap CreateImages(string code)
        {
            var result = new Bitmap(120, 36);
            var g = Graphics.FromImage(result);
            g.Clear(Color.Khaki);
            var random = new Random((int)DateTime.Now.Ticks);
            for (var i = 0; i < 12; i++)
            {
                var x1 = random.Next(result.Width);
                var x2 = random.Next(result.Width);
                var y1 = random.Next(result.Height);
                var y2 = random.Next(result.Height);
                g.DrawLine(new Pen(Color.Black), x1, y1, x2, y2);
            }
            var font = new Font("Arial", 25, FontStyle.Bold | FontStyle.Italic);
            var lgb = new LinearGradientBrush(
                new Rectangle(0, 0, result.Width, result.Height), Color.Gray, Color.Black, 1.2f, true);
            g.DrawString(code, font, lgb, 0, 0);
            for (var i = 0; i < 10; i++)
            {
                var x = random.Next(result.Width);
                var y = random.Next(result.Height);
                result.SetPixel(x, y, Color.Black);
            }
            g.DrawRectangle(new Pen(Color.DimGray), 0, 0, result.Width - 1, result.Height - 1);
            return result;
        }