public const string SESSION_VAR_NAME = "RandomStr"; protected void Page_Load(object sender, EventArgs e) { //http://msdotnetsupport.blogspot.com/2008/04/implement-simple-captcha-in-cnet.html 내용을 참고하였다. //대조하는 방법도 해당 페이지를 참고한다. //TODO: 좀더 다양한 색상, 글꼴 스타일 등등 Bitmap objBMP = new Bitmap(100, 30); Graphics objGraphics = Graphics.FromImage(objBMP); objGraphics.Clear(Color.Wheat); objGraphics.TextRenderingHint = TextRenderingHint.AntiAlias; //' Configure font to use for text Font objFont = new Font("Arial", 14, FontStyle.Italic); string randomStr = ""; char[] myArray = new char[5]; int x; //That is to create the random # and add it to our string Random autoRand = new Random(); for (x = 0; x < 5; x++) { myArray[x] = System.Convert.ToChar(autoRand.Next(65, 90)); randomStr += (myArray[x].ToString()); } //This is to add the string to session, to be compared later Session.Add(SESSION_VAR_NAME, randomStr); //' Write out the Text objGraphics.DrawString(randomStr, objFont, Brushes.Red, 3, 3); //' Set the content type and return the image Response.Buffer = false; Response.Clear(); Response.ContentType = "image/GIF"; objBMP.Save(Response.OutputStream, ImageFormat.Gif); objFont.Dispose(); objGraphics.Dispose(); objBMP.Dispose(); Response.Flush(); Response.End(); }