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This article mainly introduces "how to use .net to generate CAPTCHA". In daily operation, I believe that many people have doubts about how to use .net to generate CAPTCHA. The editor consulted all kinds of data and sorted out simple and easy-to-use operation methods. I hope it will be helpful for you to answer the doubts about how to use .net to generate CAPTCHA. Next, please follow the editor to study!

First of all, let me show you the effect picture:

Page code:

Function change () {var img = document.getElementById ("ValidateCode"); img.src = img.src +'?;} CAPTCHA

Get another one.

Background code:

/ sign in / protected void LoginSubmits (object sender, EventArgs e) {CheckLogin ();} # region Private method # region public static Boolean IsNotNull (Object str) {return! IsNull (str);} public static Boolean IsNull (Object str) {return str = = null } public static void Show (System.Web.UI.Page page, string msg) {page.ClientScript.RegisterStartupScript (page.GetType (), "message", "alert ('" + msg.ToString () + ");");} # endregion private void CheckLogin () {if (tbCheckCode.Text.Trim () = = "") {Show (this, "CAPTCHA cannot be empty!"); return } else {if (IsNotNull (Session ["ValidateCheckCode"])) {if (tbCheckCode.Text.Trim ()! = Session ["ValidateCheckCode"] .ToString ()) {Show (this, "incorrect verification code!"); tbCheckCode.Text = "; return }} else {Show (this, "Please refresh CAPTCHA!") ; return;}} # endregion}}

Generate a CAPTCHA:

Using System;using System.Drawing;using System.Text;using System.Web;namespace Web.TEXT {public partial class VerifyCode: System.Web.UI.Page {public Encoding GB = Encoding.GetEncoding ("GB2312"); protected void Page_Load (object sender, EventArgs e) {VerifyCode v = new VerifyCode (); v.Length = this.length; v.FontSize = this.fontSize; v.Chaos = this.chaos; v.BackgroundColor = this.backgroundColor V.ChaosColor = this.chaosColor; v.CodeSerial = this.codeSerial; v.Colors = this.colors; v.Fonts = this.fonts; v.Padding = this.padding; string code = v.CreateVerifyCode (); / take the random code v.CreateImageOnPage (code, this.Context); / / output the picture Response.Cookies.Add (new HttpCookie ("CheckCode", code.ToUpper () / / use Cookies to fetch the value of the verification code System.Web.HttpContext.Current.Session ["ValidateCheckCode"] = code; / / return checkCode;} # region verification code length (the default length of 4 verification codes) private int length = 4; public int Length {get {return length;} set {length = value }} # endregion # region captcha font size (the default is 40 pixels for distorting effects, which can be modified by yourself) private int fontSize = 12; public int FontSize {get {return fontSize;} set {fontSize = value;} # endregion # region border patch (default 1 pixel) private int padding = 1; public int Padding {get {return padding } set {padding = value;}} # endregion # region whether to output the dry point (not output by default) private bool chaos = true; public bool Chaos {get {return chaos;} set {chaos = value;}} # endregion # region output dry point color (default gray) private Color chaosColor = Color.LightGray; public Color ChaosColor {get {return chaosColor } set {chaosColor = value;}} # endregion # region Custom background Color (default white) private Color backgroundColor = Color.White; public Color BackgroundColor {get {return backgroundColor;} set {backgroundColor = value } # endregion # region custom random color array private Color [] colors = {Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple}; public Color [] Colors {get {return colors;} set {colors = value }} # endregion # region Custom Font Array private string [] fonts = {"Arial", "Georgia"}; public string [] Fonts {get {return fonts;} set {fonts = value;}} # endregion # region Custom Random Code string sequence (separated by commas) private string codeSerial = "0meme 1m 2m 3m 4m 5e 6m 7e 8e 9" / / string codeSerial = "0memorial2meme3precriminal5peme7precalewrecewrecewrecedjrewrecewrecedwrecedwrecedwrecedwrecedwrecedwrecedwrecedwforcewrecedwrecedforwwrecedwrecedwrecedwrecewrecedforforcewrecedwrecewrecedforforcewrecedwrecedforforcewrecewrecedforforcewrecewrecedforforcewrecedforformaitywrecedforforgivingwrecedforforgivedforcewrecryforforgivingwrecewrecedforforgivedforcewrecewrecedforforcewrecedforforcewrecedforcedforcewrecryformaityforforcewrecedforwrecedforwrecedformaitywrecedwrecedforwrecewrecewrecedforwrecewrecewrecewrecew / / string codeSerial = "Gan, Yang, Yang, Yi, chair, ant, Yi, Yi, Win, Ying, Yong, Yong, Yu, Yu Zhu, Zi, Zi Zi, Zong, Zou, Zou, walking, playing, beating, renting, foot, pawn, clan, ancestor, curse, hindrance, group, drill, codify, mouth, drunken, most, sin, respect, obedience, yesterday, left, Zuo, tussah, do, work, sit, seat. " Public string CodeSerial {get {return codeSerial;} set {codeSerial = value;} # endregion / / generate Waveform filter effect # region generate Waveform filter effect private const double PI = 3.1415926535897932384626433832795; private const double PI2 = 6.283185307179586476925286766559 / * / sinusoidal Wave distorts the picture (Edit By 51aspx.com) / Picture path / if distorted, choose the amplitude multiple of the True / waveform. The larger the distortion, the higher the distortion, which is generally the starting phase of the 3 / / waveform. Value range: [0-2*PI) / / public System.Drawing.Bitmap TwistImage (Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase) {System.Drawing.Bitmap destBmp = new Bitmap (srcBmp.Width, srcBmp.Height) / / fill the bitmap background with white 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 # region generate check code picture public Bitmap CreateImageCode (string code) {int fSize = FontSize; int fWidth = fSize + Padding; int imageWidth = (int) (code.Length*fWidth) + 4 + Padding*2 Int imageHeight = fSize*2 + Padding; System.Drawing.Bitmap image = new System.Drawing.Bitmap (imageWidth, imageHeight); Graphics g = Graphics.FromImage (image); g.Clear (BackgroundColor); Random rand = new Random (); / / add a randomly generated dry point if (this.Chaos) {Pen pen = new Pen (ChaosColor, 0) to the background; int c = Length*10 For (int I = 0; I < c; iTunes +) {int x = rand.Next (image.Width); int y = rand.Next (image.Height); g.DrawRectangle (pen, x, y, 1,1);}} int left = 0, top = 0, top1 = 1, top2 = 1; int N1 = (imageHeight-FontSize-Padding*2); int N2 = N1 Top1 = N2; top2 = N2; Font f; Brush b; int cindex, findex; # region CAPTCHA characters for (int I = 0; I < code.Length; iCAPTCHA +) {cindex = rand.Next (Colors.Length-1); findex = rand.Next (Fonts.Length-1) F = new System.Drawing.Font (Fonts [findex], fSize, System.Drawing.FontStyle.Bold); b = new System.Drawing.SolidBrush (Colors [c index]); if (I% 2 = = 1) {top = top2;} else {top = top1;} left = i*fWidth G.DrawString (code.Substring (I, 1), f, b, left, top);} / draw a border color Color.Gainsboro g.DrawRectangle (new Pen (Color.Gainsboro, 0), 0,0, image.Width-1, image.Height-1); g.Dispose (); / / generate waveforms / / image = TwistImage (image, true, 8,4); return image } # endregion / / output the created image to the page public void CreateImageOnPage (string code, HttpContext context) {System.IO.MemoryStream ms = new System.IO.MemoryStream (); Bitmap image = this.CreateImageCode (code); image.Save (ms, System.Drawing.Imaging.ImageFormat.Jpeg); context.Response.ClearContent (); context.Response.ContentType = "image/Jpeg"; context.Response.BinaryWrite (ms.GetBuffer ()) Ms.Close (); ms = null; image.Dispose (); image = null;} # endregion # region generate random character codes public string CreateVerifyCode (int codeLen) {if (codeLen = = 0) {codeLen = Length;} string [] arr = CodeSerial.Split (','); string code = "; int randValue =-1 Random rand = new Random (unchecked ((int) DateTime.Now.Ticks)); for (int I = 0; I < codeLen; iTunes +) {randValue = rand.Next (0, arr.Length-1); code + = arr [randValue];} return code;} public string CreateVerifyCode () {return CreateVerifyCode (0) } # endregion}} at this point, the study on "how to use. Net to generate CAPTCHA" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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