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說到驗證碼,應該是老話重提,不用說,大家都知道驗證碼的重要性,以前做asp的時候,直接調用别人寫的幾個asp檔案,然後
就ok了,并沒有深入的去學習這些驗證碼是如何生成的,直到學習了.net的GDI+,看了下驗證碼的代碼之後,才明了,其實驗證碼就是那麼回事.
驗證碼無非是用到了.net類庫中的System.Drawing中的一些類,比如Imaging,Drawing2D等
下面我們通過一個asp.net驗證碼的例子來了解一下這些數字是如何生成的,又是如何将之畫上圖檔上去的
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
public partial class CheckCode : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
this.CreateCheckCodeImage(GenerateCheckCode());
}
//生成随機數
private string GenerateCheckCode()
{
int number;
char code;
string checkCode = String.Empty;
System.Random random = new Random();
for (int i = 0; i < 4; i++)
{
number = random.Next();
if (number % 2 == 0) // 如果是個偶數
code = (char)('0' + (char)(number % 10));
else
code = (char)('A' + (char)(number % 26));
checkCode += code.ToString();
}
Session["CheckCode"] = checkCode;
return checkCode;
}
//将随機數寫入圖檔
private void CreateCheckCodeImage(string checkCode)
{
if (checkCode == null || checkCode.Trim() == String.Empty)
return;
//Math.Celling方法是傳回大于或等于指定數字的最小整數
System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);
Graphics g = Graphics.FromImage(image);
try
{
//生成随機生成器
Random random = new Random();
//清空圖檔背景色
g.Clear(Color.White);
//畫圖檔的背景噪音線
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);
//畫線需要四個值,即起點的坐标(x1,y1)和末點的坐标(x2,y2)
g.DrawLine(new Pen(Color.GreenYellow), x1, y1, x2, y2);
}
Font font = new System.Drawing.Font("Verdana", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
//通過定義一個筆刷來畫一個長方形
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(checkCode, font, brush, 2, 2);
//畫圖檔的前景噪音點
for (int i = 0; i < 80; i++)
{
int x = random.Next(image.Width);
int y = random.Next(image.Height);
image.SetPixel(x, y, Color.FromArgb(random.Next()));
}
//畫圖檔的邊框線
g.DrawRectangle(new Pen(Color.Red), 0, 0, image.Width - 1, image.Height - 1);
//定義一個記憶體流
System.IO.MemoryStream ms = new System.IO.MemoryStream();
image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);//圖檔儲存格式為gif
Response.ClearContent();
Response.ContentType = "image/Gif";
Response.BinaryWrite(ms.ToArray());//将二進制字元串寫入Http輸出流中
}
finally
{
g.Dispose();
image.Dispose();
}
}
}
代碼也不難,大家可以看下Drawing類,常用的畫圖方法我都标明了
我這邊是将随機數寫入session中,當然你也可以寫入cookie
Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));
要使用驗證碼也很容易,隻要将之儲存為xxx.aspx
使用的時候
就ok了
轉自部落格園 jacky song