一个图片验证码的实现

其实实现一个图片验证码并不是什么难的问题,主要讲究的时验证的实现上如何提高程序的识别难度.所以在实现过程参考了一下google的做法,由于数字或字母适当重叠对人自身识别并不成什么问题,但对于计算增加的难度相对来说就比较高些了.如果感觉难度不大可以调整一下程序让让字母之间紧靠的近一点,也可适当地加下曲线来让分析上更难.不过做得太过的话,估计人自己都搞不清楚了:)

验证码效果

 

具体实现代码

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using System; using System.Collections.Generic; using System.Drawing; using System.Drawing.Drawing2D; using System.Text;   namespace Smark.ImageNumber {     ///     /// Copyright © henryfan 2012            /// Email:  henryfan@msn.com        /// HomePage:   http://www.ikende.com           /// CreateTime: 2012/10/23 21:18:29     ///     public class Generator     {         const string VALUE = "123456789";           private static Dictionary mCharImages = new Dictionary(26);           private static Image mLine;           private static Random mRam = new Random();           public static string GeneratorCode()         {             string code = "";             for (int i = 0; i < 4; i++)             {                 code += VALUE.Substring(GetRamValue() % VALUE.Length, 1);             }             return code;           }           static int GetRamValue()         {               return mRam.Next();         }           public static Image GetImage(string code)         {             Bitmap tmpImg = new Bitmap(100, 40);             using (Graphics e = Graphics.FromImage(tmpImg))             {                   int offset = 2;                   e.FillRectangle(new SolidBrush(Color.White), 0, 0, 200, 60);                   List items = new List();                 foreach (char key in code)                 {                     items.Add(GetGeneratorItem(key));                 }                 for (int i = 0; i < items.Count; i++)                 {                     if (i > 0)                     {                         if ((items[i].Value < 0 && items[i - 1].Value > 0) || (items[i].Value > 0 && items[i - 1].Value > 0)                             || (items[i].Value < 0 && items[i - 1].Value < 0))                             offset += 12;                           else                             offset += 18;                     }                     using (Image img = items[i].DrawImage())                     {                         if (Math.Abs(items[i].Value) > 20)                             e.DrawImage(img, offset, 6);                         else if (Math.Abs(items[i].Value) > 20)                             e.DrawImage(img, offset, 4);                         else                             e.DrawImage(img, offset, 2);                     }                   }                 }             return tmpImg;         }           public static System.Collections.IEnumerable GetKeys         {             get             {                 return mCharImages.Keys;             }         }           private static GeneratorItem GetGeneratorItem(char key)         {             GeneratorItem item = new GeneratorItem();             int value = GetRamValue() % 25;             if (value < 10)                 value = 10;             if (GetRamValue() % 2 == 0)                 value = -value;             item.Value = value;             item.Key = key;             return item;         }           class GeneratorItem         {             public int Value { get; set; }             public char Key { get; set; }             public Image DrawImage()             {                 Bitmap tmpImg = new Bitmap(50, 50);                 using (Graphics e = Graphics.FromImage(tmpImg))                 {                     e.RotateTransform(Value, System.Drawing.Drawing2D.MatrixOrder.Append);                     e.DrawImage(mCharImages[Key], 0, 0);                     e.Flush();                 }                 return tmpImg;             }         }           static Generator()         {               HatchBrush sb = new HatchBrush(HatchStyle.Percent40, Color.Black, Color.Black);               foreach (char item in VALUE)             {                   Bitmap bmp = new Bitmap(50, 50);                 using (Graphics g = Graphics.FromImage(bmp))                 {                     g.DrawString(new string(new char[] { item }), new Font("宋体", 24, FontStyle.Italic), sb, 2, 2);                 }                 mCharImages[item]= bmp;             }               mLine = new Bitmap(60, 4);             using (Graphics g = Graphics.FromImage(mLine))             {                 g.FillRectangle(sb, 0, 0, 60, 3);             }           }     } }