驗證碼技術是網站開發過程中比較重要的技術,可以防止非法人員利用注冊機或者登陸工具來攻擊我們的網站。下面是效果圖:
具體實現方法如下:
1、主要思路是:引用Using System.Drawing命名空間,利用Graphics的FromImage方法創建一個畫布,同時設置畫布的寬和高,然後通過Graphics類 的DrawString方法隨機生成的字符串繪制到畫布中,繪制驗證碼的同時,在畫布中利用SetPixel方法繪制一些色點,從而防止非法人員利用機器 人來進行登陸。當我們繪制驗證碼完畢後,在需要驗證碼的頁面中利用Image空間將其顯示出來,Image控件顯示驗證碼的HTML源碼設置如下:
<asp:Image ID="Image1" runat="server"ImageUrl="~/ValidateNum.aspx" /> <asp:LinkButton ID="LinkButton1" runat="server" style="font-size: small; ">看不清,換一張</asp:LinkButton>
2、這裡所用到的ValidateNum.aspx頁面代碼如下:
using System; using System.Collections; using System.Configuration; using System.Data; using System.Linq; using System.Web; using System.Web.Security; using System.Web.UI; using System.Web.UI.HtmlControls; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Xml.Linq; using System.Drawing; public partial class ValidateNum : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { string validateNum = CreateRandomNum(4);//成生4位隨機字符串 CreateImage(validateNum);//將生成的隨機字符串繪成圖片 Session["ValidateNum"] = validateNum;//保存驗證碼 } } //生成隨機字符串 private string CreateRandomNum(int NumCount) { string allChar = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,W,X,Y,Z"; string[] allCharArray = allChar.Split(',');//拆分成數組 string randomNum = ""; int temp = -1;//記錄上次隨機數的數值,盡量避免產生幾個相同的隨機數 Random rand = new Random(); for (int i = 0; i < NumCount; i++) { if (temp != -1) { rand = new Random(i * temp * ((int)DateTime.Now.Ticks)); } int t = rand.Next(35); if (temp == t) { return CreateRandomNum(NumCount); } temp = t; randomNum += allCharArray[t]; } return randomNum; } //生成圖片 private void CreateImage(string validateNum) { if (validateNum == null || validateNum.Trim() == String.Empty) return; //生成Bitmap圖像 System.Drawing.Bitmap image = new System.Drawing.Bitmap(validateNum.Length * 12 + 10, 22); Graphics g = Graphics.FromImage(image); try { //生成隨機生成器 Random random = new Random(); //清空圖片背景色 g.Clear(Color.White); //畫圖片的背景噪音線 for (int i = 0; i < 25; i++) { int x1 = random.Next(image.Width); int x2 = random.Next(image.Width); int y1 = random.Next(image.Height); int y2 = random.Next(image.Height); g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2); } Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic)); System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true); g.DrawString(validateNum, font, brush, 2, 2); //畫圖片的前景噪音點 for (int i = 0; i < 100; i++) { int x = random.Next(image.Width); int y = random.Next(image.Height); image.SetPixel(x, y, Color.FromArgb(random.Next())); } //畫圖片的邊框線 g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1); System.IO.MemoryStream ms = new System.IO.MemoryStream(); //將圖像保存到指定的流 image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif); Response.ClearContent(); Response.ContentType = "image/Gif"; Response.BinaryWrite(ms.ToArray()); } finally { g.Dispose(); image.Dispose(); } } }
以上就是關於asp.net生成圖形驗證碼的相關資料,希望對大家的學習有所幫助。