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); } } } } |