对验证码识别大致分这几个过程，
- 第一步获取验证码，
- 第二对验证码处理，如果颜色单一没什么背景杂色就直接二值化处理，注意阙值，有干扰线的把干扰线和背景去掉，最终变为背景为白色，验证码前景色为黑色。
- 第三步就是切割，把验证码从图片中切割出来，
- 第四建立识别库，切割后的图片分类存入识别库，让后需要让程序学习一些验证码后，识别库就有了样例。第四步就是那当前是别的验证码和识别库的验证码进行比对，达到识别验证码的结果。
实例程序代码：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;
using System.Net;
using System.Collections;
using System.IO;
namespace CheckCodeRecognizeLib
{
public class CheckCodeRecognize
{
#region 成员变量
//色差阀值 越小消除的杂色越多
private double threshold = 150;
//二值阀值 越大效果越不明显
private double ezFZ = 0.6;
//背景近似度阀值
private double bjfz = 80;
//图片路径
private string imgPath = string.Empty;
//每个字符最小宽度
public int MinWidthPerChar = 7;
//每个字符最大宽度
public int MaxWidthPerChar = 18;
//每个字符最小高度
public int MinHeightPerChar = 10;
//学习库保存的路径
private readonly string samplePath = AppDomain.CurrentDomain.BaseDirectory + "Sample\\";
#endregion
#region 图片处理
/// <summary>
/// 对传入的图片二值化
/// </summary>
/// <param name="bitmap">传入的原图片</param>
/// <returns>处理过后的图片</returns>
private Bitmap EZH(Bitmap bitmap)
{
if (bitmap != null)
{
var img = new Bitmap(bitmap);
for (var x = 0; x < img.Width; x++)
{
for (var y = 0; y < img.Height; y++)
{
Color color = img.GetPixel(x, y);
if (color.GetBrightness() < ezFZ)
{
img.SetPixel(x, y, Color.Black);
}
else
{
img.SetPixel(x, y, Color.White);
}
}
}
return img;
}
return null;
}
/// <summary>
/// 去背景
/// 把图片中最多的一部分颜色视为背景色 选出来后替换为白色
/// </summary>
/// <param name="bitmapImg">将要处理的图片</param>
/// <returns>返回去过背景的图片</returns>
private Bitmap RemoveBackGround(Bitmap bitmapImg)
{
if (bitmapImg == null)
{
return null;
}
//key 颜色 value颜色对应的数量
Dictionary<Color, int> colorDic = new Dictionary<Color, int>();
//获取图片中每个颜色的数量
for (var x = 0; x < bitmapImg.Width; x++)
{
for (var y = 0; y < bitmapImg.Height; y++)
{
//删除边框
if (y == 0 || y == bitmapImg.Height)
{
bitmapImg.SetPixel(x, y, Color.White);
}
var color = bitmapImg.GetPixel(x, y);
var colorRGB = color.ToArgb();
if (colorDic.ContainsKey(color))
{
colorDic[color] = colorDic[color] + 1;
}
else
{
colorDic[color] = 1;
}
}
}
//图片中最多的颜色
Color maxColor = colorDic.OrderByDescending(o => o.Value).FirstOrDefault().Key;
//图片中最少的颜色
Color minColor = colorDic.OrderBy(o => o.Value).FirstOrDefault().Key;
Dictionary<int[], double> maxColorDifDic = new Dictionary<int[], double>();
//查找 maxColor 最接近颜色
for (var x = 0; x < bitmapImg.Width; x++)
{
for (var y = 0; y < bitmapImg.Height; y++)
{
maxColorDifDic.Add(new int[] { x, y }, GetColorDif(bitmapImg.GetPixel(x, y), maxColor));
}
}
//去掉和maxColor接近的颜色 即 替换成白色
var maxColorDifList = maxColorDifDic.OrderBy(o => o.Value).Where(o => o.Value < bjfz).ToArray();
foreach (var kv in maxColorDifList)
{
bitmapImg.SetPixel(kv.Key[0], kv.Key[1], Color.White);
}
return bitmapImg;
}
/// <summary>
/// 获取色差
/// </summary>
/// <param name="color1"></param>
/// <param name="color2"></param>
/// <returns></returns>
private double GetColorDif(Color color1, Color color2)
{
return Math.Sqrt((Math.Pow((color1.R - color2.R), 2) +
Math.Pow((color1.G - color2.G), 2) +
Math.Pow((color1.B - color2.B), 2)));
}
/// <summary>
/// 去掉目标干扰线
/// </summary>
/// <param name="img">将要处理的图片</param>
/// <returns>去掉干干扰线处理过的图片</returns>
private Bitmap btnDropDisturb_Click(Bitmap img)
{
if (img == null)
{
return null;
}
byte[] p = new byte[9]; //最小处理窗口3*3
//去干扰线
for (var x = 0; x < img.Width; x++)
{
for (var y = 0; y < img.Height; y++)
{
Color currentColor = img.GetPixel(x, y);
int color = currentColor.ToArgb();
if (x > 0 && y > 0 && x < img.Width - 1 && y < img.Height - 1)
{
#region 中值滤波效果不好
////取9个点的值
//p[0] = img.GetPixel(x - 1, y - 1).R;
//p[1] = img.GetPixel(x, y - 1).R;
//p[2] = img.GetPixel(x + 1, y - 1).R;
//p[3] = img.GetPixel(x - 1, y).R;
//p[4] = img.GetPixel(x, y).R;
//p[5] = img.GetPixel(x + 1, y).R;
//p[6] = img.GetPixel(x - 1, y + 1).R;
//p[7] = img.GetPixel(x, y + 1).R;
//p[8] = img.GetPixel(x + 1, y + 1).R;
////计算中值
//for (int j = 0; j < 5; j++)
//{
// for (int i = j + 1; i < 9; i++)
// {
// if (p[j] > p[i])
// {
// s = p[j];
// p[j] = p[i];
// p[i] = s;
// }
// }
//}
//// if (img.GetPixel(x, y).R < dgGrayValue)
//img.SetPixel(x, y, Color.FromArgb(p[4], p[4], p[4])); //给有效值付中值
#endregion
//上 x y+1
double upDif = GetColorDif(currentColor, img.GetPixel(x, y + 1));
//下 x y-1
double downDif = GetColorDif(currentColor, img.GetPixel(x, y - 1));
//左 x-1 y
double leftDif = GetColorDif(currentColor, img.GetPixel(x - 1, y));
//右 x+1 y
double rightDif = GetColorDif(currentColor, img.GetPixel(x + 1, y));
//左上
double upLeftDif = GetColorDif(currentColor, img.GetPixel(x - 1, y + 1));
//右上
double upRightDif = GetColorDif(currentColor, img.GetPixel(x + 1, y + 1));
//左下
double downLeftDif = GetColorDif(currentColor, img.GetPixel(x - 1, y - 1));
//右下
double downRightDif = GetColorDif(currentColor, img.GetPixel(x + 1, y - 1));
////四面色差较大
//if (upDif > threshold && downDif > threshold && leftDif > threshold && rightDif > threshold)
//{
// img.SetPixel(x, y, Color.White);
//}
//三面色差较大
if ((upDif > threshold && downDif > threshold && leftDif > threshold)
|| (downDif > threshold && leftDif > threshold && rightDif > threshold)
|| (upDif > threshold && leftDif > threshold && rightDif > threshold)
|| (upDif > threshold && downDif > threshold && rightDif > threshold))
{
img.SetPixel(x, y, Color.White);
}
List<int[]> xLine = new List<int[]>();
//去横向干扰线 原理 如果这个点上下有很多白色像素则认为是干扰
for (var x1 = x + 1; x1 < x + 10; x1++)
{
if (x1 >= img.Width)
{
break;
}
if (img.GetPixel(x1, y + 1).ToArgb() == Color.White.ToArgb()
&& img.GetPixel(x1, y - 1).ToArgb() == Color.White.ToArgb())
{
xLine.Add(new int[] { x1, y });
}
}
if (xLine.Count() >= 4)
{
foreach (var xpoint in xLine)
{
img.SetPixel(xpoint[0], xpoint[1], Color.White);
}
}
//去竖向干扰线
}
}
}
return img;
}
/// <summary>
/// 对图片先竖向分割，再横向分割
/// </summary>
/// <param name="img">将要分割的图片</param>
/// <returns>所有分割后的字符图片</returns>
private Bitmap[] SplitImage(Bitmap img)
{
if (img == null)
{
return null;
}
List<int[]> xCutPointList = GetXCutPointList(img);
List<int[]> yCutPointList = GetYCutPointList(xCutPointList, img);
Bitmap[] bitmapArr = new Bitmap[5];
//对分割的部分划线
for (int i = 0; i < xCutPointList.Count(); i++)
{
int xStart = xCutPointList[i][0];
int xEnd = xCutPointList[i][1];
int yStart = yCutPointList[i][0];
int yEnd = yCutPointList[i][1];
if (i >= 4) break;
bitmapArr[i]= (Bitmap)AcquireRectangleImage(img,
new Rectangle(xStart, yStart, xEnd - xStart + 1, yEnd - yStart + 1));
}
return bitmapArr;
}
/// <summary>
/// 分别从图片的上下寻找像素点大于阙值的地方，然后获取有黑色像素的有效区域
/// </summary>
/// <param name="xCutPointList">x轴范围的x坐标集合</param>
/// <param name="img">目标图片</param>
/// <returns>y轴坐标开始和结束点，其实就是黑色像素图片的有效区域</returns>
private List<int[]> GetYCutPointList(List<int[]> xCutPointList, Bitmap img)
{
List<int[]> list = new List<int[]>();
//获取图像最上面Y值
int topY = 0;
//获取图像最下面的Y值
int bottomY = 0;
foreach (var xPoint in xCutPointList)
{
for (int ty = 1; ty < img.Height; ty++)
{
int xStart = xPoint[0];
int xEnd = xPoint[1];
int blackCount = GetBlackPXCountInY(ty, 2, xStart, xEnd, img);
if (blackCount > 3)
{
topY = ty;
break;
}
}
for (int by = img.Height; by > 1; by--)
{
int xStart = xPoint[0];
int xEnd = xPoint[1];
int blackCount = GetBlackPXCountInY(by, -2, xStart, xEnd, img);
if (blackCount > 3)
{
bottomY = by;
break;
}
}
list.Add(new int[] { topY, bottomY });
}
return list;
}
/// <summary>
/// 获取分割后某区域的黑色像素
/// </summary>
/// <param name="startY"></param>
/// <param name="offset"></param>
/// <param name="startX"></param>
/// <param name="endX"></param>
/// <param name="img"></param>
/// <returns></returns>
private int GetBlackPXCountInY(int startY, int offset, int startX, int endX, Bitmap img)
{
int blackPXCount = 0;
int startY1 = offset > 0 ? startY : startY + offset;
int offset1 = offset > 0 ? startY + offset : startY;
for (var x = startX; x <= endX; x++)
{
for (var y = startY1; y < offset1; y++)
{
if (y >= img.Height)
{
continue;
}
if (img.GetPixel(x, y).ToArgb() == Color.Black.ToArgb())
{
blackPXCount++;
}
}
}
return blackPXCount;
}
/// <summary>
/// 获取一个垂直区域内的黑色像素
/// </summary>
/// <param name="startX">开始x</param>
/// <param name="offset">左偏移像素</param>
/// <returns></returns>
private int GetBlackPXCountInX(int startX, int offset, Bitmap img)
{
int blackPXCount = 0;
for (int x = startX; x < startX + offset; x++)
{
if (x >= img.Width)
{
continue;
}
for (var y = 0; y < img.Height; y++)
{
if (img.GetPixel(x, y).ToArgb() == Color.Black.ToArgb())
{
blackPXCount++;
}
}
}
return blackPXCount;
}
/// <summary>
/// 获取竖向分割点
/// </summary>
/// <param name="img"></param>
/// <returns>List int[xstart xend]</returns>
private List<int[]> GetXCutPointList(Bitmap img)
{
//分割点 List<int[xstart xend]>
List<int[]> xCutList = new List<int[]>();
int startX = -1;//-1表示在寻找开始节点
for (var x = 0; x < img.Width; x++)
{
if (startX == -1)//开始点
{
int blackPXCount = GetBlackPXCountInX(x, 2, img);
//如果大于有效像素则是开始节点 ,0-x的矩形区域大于3像素，认为是字母，防止一些噪点被切割
if (blackPXCount > 5)
{
startX = x;
}
}
else//结束点
{
if (x == img.Width - 1)//判断是否最后一列
{
xCutList.Add(new int[] { startX, x });
break;
}
else if (x >= startX + MinWidthPerChar)//隔开一定距离才能结束分割
{
int blackPXCount = GetBlackPXCountInX(x, 2, img);//判断后面区域黑色像素点的个数
//小于等于阀值则是结束节点
if (blackPXCount < 2)
{
if (x > startX + MaxWidthPerChar)//尽量控制不执行
{
//大于最大字符的宽度应该是两个字符粘连到一块了 从中间分开
int middleX = startX + (x - startX) / 2;
xCutList.Add(new int[] { startX, middleX });
xCutList.Add(new int[] { middleX + 1, x });
}
else
{
//验证黑色像素是否太少
blackPXCount = GetBlackPXCountInX(startX, x - startX, img);
if (blackPXCount <= 10)
{
startX = -1;//重置开始点
}
else
{
xCutList.Add(new int[] { startX, x });
}
}
startX = -1;//重置开始点
}
}
}
}
return xCutList;
}
/// <summary>
/// 截取图像的矩形区域
/// </summary>
/// <param name="source">源图像对应picturebox1</param>
/// <param name="rect">矩形区域，如上初始化的rect</param>
/// <returns>矩形区域的图像</returns>
private Image AcquireRectangleImage(Image source, Rectangle rect)
{
if (source == null || rect.IsEmpty) return null;
//Bitmap bmSmall = new Bitmap(rect.Width, rect.Height, System.Drawing.Imaging.PixelFormat.Format32bppRgb);
Bitmap bmSmall = new Bitmap(rect.Width, rect.Height, source.PixelFormat);
using (Graphics grSmall = Graphics.FromImage(bmSmall))
{
grSmall.DrawImage(source,
new System.Drawing.Rectangle(0, 0, bmSmall.Width, bmSmall.Height),
rect,
GraphicsUnit.Pixel);
grSmall.Dispose();
}
return bmSmall;
}
#endregion
#region 图片识别
/// <summary>
/// 返回两图比较的相似度 最大1
/// </summary>
/// <param name="compareImg">对比图</param>
/// <param name="mainImg">要识别的图</param>
/// <returns></returns>
private double CompareImg(Bitmap compareImg, Bitmap mainImg)
{
int img1x = compareImg.Width;
int img1y = compareImg.Height;
int img2x = mainImg.Width;
int img2y = mainImg.Height;
//最小宽度
double min_x = img1x > img2x ? img2x : img1x;
//最小高度
double min_y = img1y > img2y ? img2y : img1y;
double score = 0;
//重叠的黑色像素
for (var x = 0; x < min_x; x++)
{
for (var y = 0; y < min_y; y++)
{
if (compareImg.GetPixel(x, y).ToArgb() == Color.Black.ToArgb()
&& compareImg.GetPixel(x, y).ToArgb() == mainImg.GetPixel(x, y).ToArgb())
{
score++;
}
}
}
double originalBlackCount = 0;
//对比图片的黑色像素
for (var x = 0; x < img1x; x++)
{
for (var y = 0; y < img1y; y++)
{
if (Color.Black.ToArgb() == compareImg.GetPixel(x, y).ToArgb())
{
originalBlackCount++;
}
}
}
return score / originalBlackCount;
}
/// <summary>
/// 用所有的学习的图片对比当前图，通过黑色和图片比率获取最大相似度的字符图片，从而识别
/// </summary>
/// <param name="imgArr">要识别图片的数组</param>
/// <returns>识别后的字符串</returns>
public string RecognizeCheckCodeImg(Bitmap bitImg)
{
Bitmap EZHimg = EZH(bitImg);
Bitmap[] imgArr = SplitImage(EZHimg);
string returnString = string.Empty;
for (int i = 0; i < imgArr.Length; i++)
{
if (imgArr[i] == null)
{
continue;
}
var img = imgArr[i];
if (img == null)
{
continue;
}
string[] detailPathList = Directory.GetDirectories(samplePath);
if (detailPathList == null || detailPathList.Length == 0)
{
continue;
}
string resultString = string.Empty;
//config.txt 文件中指定了识别字母的顺序
string configPath = samplePath + "config.txt";
if (!File.Exists(configPath))
{
Console.WriteLine("config.txt文件不存在,无法识别");
return null;
}
string configString = File.ReadAllText(configPath);
double maxRate = 0;//相似度 最大1
foreach (char resultChar in configString)
{
string charPath = samplePath + resultChar.ToString();//特征目录存储路径
if (!Directory.Exists(charPath))
{
continue;
}
string[] fileNameList = Directory.GetFiles(charPath);
if (fileNameList == null || fileNameList.Length == 0)
{
continue;
}
foreach (string filename in fileNameList)
{
Bitmap imgSample = new Bitmap(filename);
//过滤宽高相差太大的
if (Math.Abs(imgSample.Width - img.Width) >= 2
|| Math.Abs(imgSample.Height - img.Height) >= 3)
{
continue;
}
//当前相似度
double currentRate = CompareImg(imgSample, img);
if (currentRate > maxRate)
{
maxRate = currentRate;
resultString = resultChar.ToString();
}
imgSample.Dispose();
}
}
returnString = returnString + resultString;
}
return returnString;
}
#endregion
}
}
程序验证：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.Drawing;
using System.IO;
namespace CheckCodeRecognizeLibTest
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("正在下载验证码......");
//CookieContainer cc = new CookieContainer();
//byte[] imgByte = HttpWebRequestForBPMS.GetWebResorce("http://hd.cnrds.net/hd/login.do?action=createrandimg",cc);
//MemoryStream ms1 = new MemoryStream(imgByte);
// Bitmap bm = (Bitmap)Image.FromStream(ms1);
Bitmap img = HttpWebRequestForBPMS.GetWebImage("http://hd.cnrds.net/hd/login.do?action=createrandimg");
Console.WriteLine("验证码下载成功，正在识别.....");
CheckCodeRecognizeLib.CheckCodeRecognize regImg = new CheckCodeRecognizeLib.CheckCodeRecognize();
string regResult= regImg.RecognizeCheckCodeImg(img);
Console.WriteLine("验证码识别成功，验证码结果为："+regResult);
}
}
}
原文：http://www.cnblogs.com/fuchongjundream/p/5403193.html