比来有伴侣在搞一个对象，已经做的挺不错了，最后想再完美一点，于是乎就提议把这种验证码给K.O.了，于是乎就K.O.了这个验证码。到达单个图片识别时间小于200ms，500个样本人工统计正确率为95%。由于本人没有相关经验，是摸着石头过河。本着经验分享的精神，分享一下整个分析的思路。在列位大神面前献丑了。
再来看看部分识别功效如下图所示：
这里是不是看着很眼熟？下面再来具体分析一下。
措置惩罚惩罚第一步 去配景噪音和二值化
对付这一块，考虑了几种要领。
要领一：统计图片颜色漫衍，颜色占有率低的判定为配景噪音。由于配景噪音和前景色区分并不明显，测验考试了很多种取景要领都不能很好去除配景噪音，最终放弃了这种要领。
要领二：事后在网上稍微查了下，比来对照风行计算灰度后设定一个阈值进行二值化。其实所谓的灰度图片道理是按照人眼对色彩敏感度取了权值，这个权值对计算机来说没有什么意义。稍微想一下就可以发明，这两个过程完全可以合并。于是乎我一步完成了去配景噪音和二值化。阈值设置为RGB三分量之和到500。功效非常令人对劲。
措置惩罚惩罚第二步 制作字符样本
样本对付计算机来说长短常重要的，因为计算机很难有逻辑思维，就算有逻辑思维也要颠末恒久训练才华让你对劲。所以要用事先制作好的样本进行对照。如果你仔细不雅察看过这些验证码会发明一个bug，几乎大部分的验证码都是使用同样的字体，于是乎就人工制作了一套字体的样本。由于上一步已经有去除配景噪音的功效，可以直接操作。制作样本这一步有点简单枯燥，还需要细心。可能因为你的一个不细心会导致某个标记的识别率偏低。在这500个样本中，只发明了31个字符。幸亏是某部门的某人员还考虑到了易错的字符，例如，1和I，，0和O等。要不然这个某部门要背负更多的骂名。
措置惩罚惩罚第三步 匹配
单个匹配用了最简单最原始的二值对照，不过匹配的是匹配率而不是匹配数。我界说了相关的计分原则。大原则是“该有的有了加分，该有的没了减分，不该有的有了适度减分，可达区域外的不算分”。
由于一些标记的部分区域匹配功效跟另一些标记的完整匹配功效相似，需要把单个匹配在一个扩大的区域内择优。在必然的范畴内，找到一个最佳匹配，这个最佳匹配就是当前位置对应的标记。
完成了一次最佳匹配，可以把匹配位置向右推进一大步，若找不到合适的最佳匹配就向右推进一小步。
措置惩罚惩罚第四步 优化和调解
任何一个算法都是需要优化和调解的。此刻要找到最佳参数配置和最佳代码组织。这一步往往是需要花费最多时间和精力的。
措置惩罚惩罚第五步 验证功效
这一步呢，纯人力验证功效，统计出正确率。
思考：
功效是出来了，代码也不久不多，效果也很抱负。搞这一行的，很多时候都想要通用的。能否通用，很洪流平上在于抽象条理。本要领只是纯挚的匹配，自然不能通用，但是要领和思想倒是通用的。具体案例具体分析。至于扭曲文字、空心文字等，措置惩罚惩罚要庞大的多。网上也有一些使用第三方图像库的要领，也许那些要领会对照通用。等有空了有兴趣了继续搞一下这个主题。
实例源码：
至于这个源码要不要颁布，纠结了一段时间。网上已经有类似的商业勾当了，而且这个识别自己没有太浩劫度，再加上某系统天生的bug，此验证码自己就相当于没有设置，因此颁布此代码，仅作于学习交流。
using System.Collections.Generic; using System.Drawing; using System.IO; using System.IO.Compression; namespace Crack12306Captcha { public class Cracker { List<CharInfo> words_ = new List<CharInfo>(); public Cracker() { var bytes = new byte[] { 0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00, 0xc5, 0x58, 0xd9, 0x92, 0x13, 0x31, 0x0c, 0x94, 0x9e, 0x93, 0x0c, 0x61, 0x97, 0x2f, 0xe1, 0x58, 0xe0, 0x91, 0x9b, 0x82, 0x62, 0x0b, 0x58, 0xee, 0xff, 0xff, 0x10, 0xd8, 0xcc, 0xc8, 0xea, 0x96, 0x6c, 0x8f, 0x13, 0x48, 0xe1, 0xaa, 0x4d, 0x46, 0x96, 0x6d, 0xb5, 0x8e, 0x96, 0x67, 0x73, 0x7f, 0x3b, 0x09, 0x0e, 0x25, 0x41, 0x49, 0xa3, 0xae, 0xd7, 0x5b, 0xa9, 0xa8, 0xd5, 0xb4, 0x76, 0x02, 0x6a, 0x5c, 0x52, 0x94, 0x54, 0xed, 0x18, 0x5a, 0x7f, 0x18, 0x00, 0x00, 0x84, 0x07, 0x1b, 0x80, 0x4a, 0x9a, 0x08, 0x35, 0xb8, 0x81, 0x50, 0xe7, 0xad, 0xbe, 0xc4, 0x8e, 0xb1, 0x4f, 0x2d, 0x5f, 0xba, 0x80, 0xbb, 0xfd, 0x9a, 0xad, 0x19, 0x36, 0xe5, 0xad, 0x87, 0xf1, 0x10, 0xc0, 0x8d, 0xc6, 0x50, 0x40, 0x52, 0xf8, 0xb3, 0x98, 0x2c, 0xd6, 0xec, 0x59, 0xe7, 0x0d, 0x3e, 0x0f, 0x93, 0x3e, 0x1d, 0x02, 0x7a, 0x18, 0x8f, 0xb6, 0xc7, 0x46, 0x4e, 0x01, 0xa3, 0x96, 0xdc, 0x3a, 0x20, 0x77, 0xbf, 0x2c, 0x24, 0xe4, 0x80, 0xa9, 0x20, 0x14, 0xe5, 0x2d, 0xb5, 0x68, 0xc9, 0x55, 0x89, 0x23, 0x96, 0x82, 0xaa, 0xba, 0x58, 0xa6, 0x03, 0x38, 0x71, 0x4b, 0x29, 0xd2, 0x47, 0x80, 0xe3, 0x84, 0x91, 0xf4, 0x78, 0x43, 0x64, 0x41, 0x7b, 0x73, 0x99, 0x80, 0x42, 0x48, 0x00, 0xde, 0x00, 0x12, 0x88, 0x80, 0xdb, 0x51, 0x4a, 0x49, 0x84, 0x43, 0xf6, 0x51, 0x90, 0x27, 0x21, 0xc9, 0xf8, 0xac, 0x00, 0x4d, 0xcd, 0x46, 0x09, 0x9d, 0x15, 0x78, 0xe0, 0x00, 0x1e, 0x44, 0x2a, 0x51, 0x8c, 0xbc, 0xd3, 0xa3, 0x68, 0x8a, 0xd5, 0x3a, 0x20, 0x79, 0xba, 0x4d, 0x71, 0x4c, 0x0b, 0x91, 0x98, 0x90, 0x7b, 0x2a, 0x42, 0xc5, 0x78, 0x7a, 0xfc, 0xd5, 0x1b, 0x4b, 0x09, 0xa7, 0x27, 0x99, 0x38, 0x05, 0x01, 0xc2, 0x80, 0x39, 0x9c, 0x67, 0xbb, 0x4e, 0x7f, 0x6c, 0x33, 0xdd, 0xed, 0x87, 0x55, 0xda, 0x5d, 0xb5, 0x56, 0x33, 0xc6, 0xf9, 0xea, 0x60, 0x64, 0xcf, 0xa7, 0x41, 0xe0, 0x5c, 0x1c, 0xc4, 0xb2, 0x25, 0xa3, 0x89, 0x88, 0x8d, 0x16, 0x00, 0xb5, 0xed, 0xa5, 0x22, 0x9d, 0x52, 0x41, 0x53, 0x8d, 0x92, 0x7f, 0x31, 0x51, 0x3f, 0xa8, 0x00, 0x85, 0x8a, 0x71, 0x10, 0x92, 0x78, 0xc4, 0x59, 0x08, 0x39, 0x69, 0xa9, 0x38, 0x41, 0x48, 0xf7, 0x40, 0x5a, 0x03, 0xd5, 0x3a, 0xf5, 0xe5, 0x9d, 0x33, 0x66, 0xc3, 0xd7, 0x1f, 0xef, 0x94, 0xa0, 0x53, 0xea, 0xf4, 0x15, 0xb2, 0x1c, 0x40, 0x2d, 0xcf, 0xaf, 0xce, 0xe9, 0xd4, 0x7a, 0x89, 0x09, 0xe6, 0xdd, 0xdb, 0x0e, 0xb8, 0x58, 0xa7, 0x60, 0x37, 0xfd, 0xf2, 0xfa, 0x2c, 0x4e, 0x51, 0x87, 0x0d, 0xfc, 0x16, 0x72, 0x2a, 0x5f, 0xc0, 0x80, 0xf0, 0x54, 0xa7, 0xde, 0xfc, 0x15, 0x8b, 0x9a, 0x36, 0x3a, 0x2c, 0x62, 0xfc, 0xd4, 0x8c, 0x31, 0xb7, 0xea, 0xd7, 0x26, 0xc4, 0xaf, 0x75, 0xea, 0xdb, 0x8b, 0xff, 0x9b, 0x9b, 0x50, 0x7e, 0xfe, 0x15, 0xab, 0x17, 0x2f, 0x96, 0x96, 0xbd, 0xaa, 0x87, 0xdd, 0x77, 0xa3, 0x77, 0xd3, 0x85, 0xf0, 0xe0, 0x58, 0xd5, 0xf6, 0x8c, 0xcd, 0xc4, 0x63, 0x52, 0x12, 0x48, 0x46, 0x0f, 0x93, 0x5a, 0xe3, 0xea, 0x24, 0x67, 0x73, 0x63, 0xa0, 0xdf, 0xdf, 0x3d, 0x67, 0xf6, 0xa9, 0xfc, 0xed, 0x08, 0xe3, 0x82, 0x57, 0x08, 0x35, 0x47, 0x68, 0x9c, 0x01, 0x40, 0x87, 0x8b, 0xbd, 0x0c, 0xb3, 0xf4, 0xe1, 0x72, 0xd7, 0x54, 0x62, 0xfd, 0x40, 0xed, 0x99, 0xa6, 0x7e, 0x2b, 0xe4, 0xb4, 0xc4, 0x62, 0x0d, 0x79, 0xae, 0x1b, 0xd7, 0xf4, 0x09, 0xb7, 0xe1, 0x7c, 0x44, 0x09, 0x9a, 0xda, 0xff, 0x52, 0x6a, 0x3c, 0xe1, 0xc8, 0xd7, 0xbd, 0xbb, 0xbe, 0x37, 0xfc, 0xd6, 0xd5, 0x4e, 0x3c, 0x40, 0x2a, 0x4b, 0x39, 0x1a, 0xbd, 0x2a, 0xcd, 0xc1, 0x18, 0x59, 0x40, 0x62, 0x78, 0xec, 0x63, 0x19, 0x72, 0xf0, 0xcf, 0xf8, 0x38, 0xfa, 0x42, 0x3a, 0xc8, 0x02, 0xec, 0x5b, 0xeb, 0x8d, 0xae, 0xf1, 0x45, 0xdd, 0x32, 0x98, 0x35, 0x3c, 0x9f, 0xa6, 0x3d, 0xce, 0x13, 0xce, 0x94, 0x38, 0x87, 0x00, 0x8d, 0x85, 0xc4, 0x70, 0x17, 0x26, 0x0e, 0xa6, 0x1e, 0x16, 0xcb, 0xbf, 0x52, 0xdf, 0x29, 0x63, 0xc4, 0xf6, 0x8c, 0x35, 0xba, 0xf2, 0xf9, 0x1f, 0xbf, 0x73, 0x1f, 0x91, 0x1b, 0x9e, 0x24, 0x5e, 0x63, 0x22, 0x82, 0x23, 0x05, 0x19, 0xb9, 0x71, 0x73, 0xdc, 0xcf, 0x05, 0x88, 0x94, 0x71, 0xdb, 0xdd, 0x48, 0x10, 0xd5, 0x55, 0xb3, 0x52, 0xc3, 0x1b, 0x01, 0x94, 0x13, 0x74, 0x94, 0x3a, 0x80, 0x2f, 0x39, 0xe2, 0x75, 0x0e, 0xf2, 0xc6, 0x18, 0xdc, 0x46, 0xfc, 0xf3, 0xea, 0x14, 0x80, 0xc1, 0xce, 0x24, 0xee, 0x72, 0xed, 0x94, 0xaf, 0xfb, 0xa9, 0xaa, 0x4a, 0xe0, 0xd4, 0x22, 0xc6, 0xf0, 0x57, 0x1d, 0x8e, 0xd2, 0x90, 0xc6, 0x0c, 0xd3, 0x9a, 0x53, 0xfb, 0xd6, 0xb7, 0xdd, 0x14, 0xd4, 0xbd, 0x41, 0xa7, 0x80, 0x7b, 0x23, 0xfe, 0x34, 0x56, 0x0d, 0x96, 0x46, 0x02, 0xfe, 0xfd, 0xb2, 0x00, 0x5f, 0x01, 0x9c, 0xa0, 0x32, 0x39, 0xd7, 0x90, 0xc2, 0x6c, 0xc7, 0x4e, 0x68, 0x88, 0x7d, 0x9f, 0x9b, 0xcf, 0xa7, 0xbe, 0xa0, 0xfc, 0x18, 0x7d, 0x07, 0x5b, 0xa9, 0xbe, 0x56, 0x1f, 0x67, 0x1a, 0x4a, 0x91, 0x9c, 0x04, 0x38, 0x53, 0x6b, 0x70, 0x68, 0x8f, 0xea, 0xf4, 0x34, 0x87, 0x7f, 0x6e, 0x82, 0xc3, 0xc1, 0xab, 0x40, 0xc4, 0x50, 0x13, 0x0e, 0x33, 0x5d, 0x67, 0x7d, 0x01, 0x1f, 0xdb, 0xc0, 0x7f, 0xed, 0x87, 0x7f, 0xbc, 0x0f, 0x75, 0xe0, 0xa5, 0xba, 0xc0, 0x84, 0x3d, 0x24, 0x04, 0xe0, 0xf1, 0x16, 0x41, 0x3b, 0x74, 0xd2, 0x52, 0xc5, 0xf8, 0x7c, 0x12, 0xfb, 0xe4, 0x37, 0x5b, 0xfb, 0x57, 0x11, 0xa1, 0x18, 0x00, 0x00, }; using (var stream = new MemoryStream(bytes)) using (var gzip = new GZipStream(stream, CompressionMode.Decompress)) using (var reader = new BinaryReader(gzip)) { while (true) { char ch = reader.ReadChar(); if (ch == ‘\0‘) break; int width = reader.ReadByte(); int height = reader.ReadByte(); bool[,] map = new bool[width, height]; for (int i = 0; i < width; i++) for (int j = 0; j < height; j++) map[i, j] = reader.ReadBoolean(); words_.Add(new CharInfo(ch, map)); } } } public string Read(Bitmap bmp) { var result = string.Empty; var width = bmp.Width; var height = bmp.Height; var table = ToTable(bmp); var next = SearchNext(table, -1); while (next < width - 7) { var matched = Match(table, next); if (matched.Rate > 0.6) { result += matched.Char; next = matched.X + 10; } else { next += 1; } } return result; } private bool[,] ToTable(Bitmap bmp) { var table = new bool[bmp.Width, bmp.Height]; for (int i = 0; i < bmp.Width; i++) for (int j = 0; j < bmp.Height; j++) { var color = bmp.GetPixel(i, j); table[i, j] = (color.R + color.G + color.B < 500); } return table; } private int SearchNext(bool[,] table, int start) { var width = table.GetLength(0); var height = table.GetLength(1); for (start++; start < width; start++) for (int j = 0; j < height; j++) if (table[start, j]) return start; return start; } private double FixedMatch(bool[,] source, bool[,] target, int x0, int y0) { double total = 0; double count = 0; int targetWidth = target.GetLength(0); int targetHeight = target.GetLength(1); int sourceWidth = source.GetLength(0); int sourceHeight = source.GetLength(1); int x, y; for (int i = 0; i < targetWidth; i++) { x = i + x0; if (x < 0 || x >= sourceWidth) continue; for (int j = 0; j < targetHeight; j++) { y = j + y0; if (y < 0 || y >= sourceHeight) continue; if (target[i, j]) { total++; if (source[x, y]) count++; else count--; } else if (source[x, y]) count -= 0.55; } } return count / total; } private MatchedChar ScopeMatch(bool[,] source, bool[,] target, int start) { int targetWidth = target.GetLength(0); int targetHeight = target.GetLength(1); int sourceWidth = source.GetLength(0); int sourceHeight = source.GetLength(1); double max = 0; var matched = new MatchedChar(); for (int i = -2; i < 6; i++) for (int j = -3; j < sourceHeight - targetHeight + 5; j++) { double rate = FixedMatch(source, target, i + start, j); if (rate > max) { max = rate; matched.X = i + start; matched.Y = j; matched.Rate = rate; } } return matched; } private MatchedChar Match(bool[,] source, int start) { MatchedChar best = null; foreach (var info in words_) { var matched = ScopeMatch(source, info.Table, start); matched.Char = info.Char; if (best == null || best.Rate < matched.Rate) best = matched; } return best; } private class CharInfo { public char Char { get; private set; } public bool[,] Table { get; private set; } public CharInfo(char ch, bool[,] table) { Char = ch; Table = table; } } private class MatchedChar { public int X { get; set; } public int Y { get; set; } public char Char { get; set; } public double Rate { get; set; } } } }
使用要领如下：
var cracker = new Cracker(); var result = cracker.Read(img);