简单验证码识别

验证码识别主要包括两部分：去除干扰和识别。其中最麻烦的是去除干扰。对于识别有现成的库：tesseract。在进行验证码识别之前，首先需要得到验证码数据，如果从网上下载是在太麻烦，就写了一个生成验证码的程序，用来生成各种随机验证码。

一、生成验证码数据集

1）验证码的随机性，包括字符串本身的随机性，字体以及字体大小的随机性以及字体旋转和各种随机干扰线。

2）简单的代码：

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Linq;using System.Text;using System.Threading.Tasks;using System.Windows.Forms;namespace GenSecurityCode{    public partial class SecurityCodeGen : Form    {        public const int DEFAULT_FONT_SIZE = 20;        private int iCodeLen = 6;        private int iFontSize = DEFAULT_FONT_SIZE;        private int iInterferLines = 6;        private int iCodeNums = 20;        public string batchSavePath = string.Empty;        public SecurityCodeGen()        {            InitializeComponent();        }        private void SecurityCodeGen_Load(object sender, EventArgs e)        {            checkNum.Checked = true;            checkUpperCase.Checked = false;            checkLowerCase.Checked = false;            textCodeLength.Text = iCodeLen.ToString();            txtCodeNums.Text = iCodeNums.ToString();        }        /*Generate Security Code String         */        private string GenCodeString()        {            string codeStr = String.Empty;            char code;            System.Random random = new Random();            int iRandCode;            if (checkNum.Checked)            {                for (int i = 0; i < iCodeLen; i++)                {                    iRandCode = random.Next();                    code = (char)('0' + (char)(iRandCode % 10));                    codeStr += code.ToString();                }            }            return codeStr;        }        private System.Drawing.Bitmap GenCodeImage(string sCodeStr)        {            char[] chars = sCodeStr.ToCharArray();            //define random color            Color[] colorArray = { Color.Black, Color.Red, Color.DarkBlue, Color.Green,                             Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };            //define random font            string[] fontArray = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };            //define random transform angle            int iTransAngleRange = 0;            //define image            System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((sCodeStr.Length * iFontSize* 1.0)),                 (int)Math.Ceiling(iFontSize * 2.0));            Graphics g = Graphics.FromImage(image);            //Gen Backgroud Image;            System.Random random = new Random();            g.Clear(Color.White);            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;            //draw interferior lines            for (int i = 0; i < iInterferLines; 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);                int colorIndex = random.Next(colorArray.Length);                g.DrawLine(new Pen(colorArray[colorIndex]), x1, y1, x2, y2);            }            StringFormat format = new StringFormat(StringFormatFlags.NoClip);            format.Alignment = StringAlignment.Center;            format.LineAlignment = StringAlignment.Center;            //draw security code string            for (int i = 0; i < chars.Length; i++)            {                int fontIndex = 1;//random.Next(5);//no random font used first                int colorIndex = random.Next(colorArray.Length);                int transAngleIndex = 0;// no transform first;                Font font = new System.Drawing.Font(fontArray[fontIndex], iFontSize, System.Drawing.FontStyle.Bold);                Point dot = new Point(iFontSize/8, iFontSize/8);                Brush brush = new System.Drawing.SolidBrush(colorArray[colorIndex]);                                float angle = random.Next(-transAngleIndex, transAngleIndex);                g.TranslateTransform(dot.X, dot.Y);                g.RotateTransform(angle);                g.DrawString(chars[i].ToString(), font, brush, 1, 1);                //MessageBox.Show(chars[i].ToString());                g.RotateTransform(-angle);                g.TranslateTransform((int)Math.Ceiling(iFontSize*0.75), -dot.Y);                //g.DrawString(sCodeStr.ToString(), font, brush, 1, 1);            }                        //draw interferior point            for (int i = 0; i < 150; i++)            {                int x = random.Next(image.Width);                int y = random.Next(image.Height);                image.SetPixel(x, y, Color.FromArgb(random.Next()));            }            //draw border            //g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);            return image;        }        private void btnGen_Click(object sender, EventArgs e)        {            string codeStr = GenCodeString();            System.Drawing.Bitmap image = GenCodeImage(codeStr);            txtCodeStr.Text = codeStr;            this.picShowCtrl.Width = image.Width;            this.picShowCtrl.Height = image.Height;            this.picShowCtrl.BackgroundImage = image;            image.Save(codeStr + ".jpg");        }        private void btnBatchGen_Click(object sender, EventArgs e)        {            if (batchSavePath.Length == 0)            {                FolderBrowserDialog folderDlg = new FolderBrowserDialog();                folderDlg.ShowDialog();                batchSavePath = folderDlg.SelectedPath;                if (batchSavePath.Length == 0)                {                    MessageBox.Show("You didn't select path!");                }            }            iCodeNums = int.Parse(txtCodeNums.Text);            iCodeLen = int.Parse(textCodeLength.Text);            txtCodeStr.Text = string.Empty;            for (int i = 0; i < iCodeNums; i++)            {                string codeStr = GenCodeString();                System.Drawing.Bitmap image = GenCodeImage(codeStr);                if (txtCodeStr.Text.Length != 0)                    //txtCodeStr.Text += Environment.NewLine +codeStr;                    txtCodeStr.Text += "," + codeStr;                else                    txtCodeStr.Text = codeStr;                if(batchSavePath.Length==0)                    image.Save(codeStr + ".jpg");                else                    image.Save(batchSavePath+"\\"+codeStr + ".jpg");                System.Threading.Thread.Sleep(50);            }        }    }}

二、去除干扰

Mat PreProcess(Mat &img){Mat grayImg,binaryImg,erodeImg,dilateImg,maskedImg;cvtColor(img, grayImg, CV_RGB2GRAY);Mat mask(img.rows, img.cols, CV_8UC1,Scalar(0));/*OSTU threshold*/threshold(grayImg, binaryImg, 0, 255, CV_THRESH_OTSU + CV_THRESH_BINARY_INV);imwrite("binary.jpg", binaryImg);/*erode to remove noise,erode and dilate function only work on white pixel*/erode(binaryImg, erodeImg, Mat(2, 2, CV_8U), Point(-1, -1), 1);imwrite("erode.jpg", erodeImg);/*dilate to link contour*/dilate(erodeImg, dilateImg, Mat(3, 3, CV_8U), Point(-1, -1), 1);imwrite("dilate.jpg", dilateImg);dilateImg.copyTo(grayImg);/*find contour*/vector<vector<Point>> contours;findContours(dilateImg, contours, CV_RETR_EXTERNAL, CV_CHAIN_APPROX_NONE);imwrite("dilate1.jpg", grayImg);/*remove interferior*/vector<vector<Point>>::iterator it;Point2f center;float radius;Rect rc;for (it = contours.begin(); it != contours.end();){minEnclosingCircle(*it, center, radius);if (center.y > (img.rows / 4) && center.y < img.rows * 3 / 4){

<span style="white-space:pre"></span>/*you can add more condition to remove more interferior*/rc = boundingRect(*it);rectangle(mask, rc, CV_RGB(255,255,255), -1);it++;}else{/*please note how to erase one item in vector*/it = contours.erase(it);}}imwrite("mask.jpg", mask);//copy(dilateImg, maskedImg, mask);grayImg.copyTo(maskedImg, mask);erode(maskedImg, erodeImg, Mat(2, 2, CV_8U), Point(-1, -1), 1);bitwise_not(erodeImg, erodeImg);imwrite("masked.jpg", erodeImg);return erodeImg;}

三、字符识别

字符识别最麻烦其实是tesseract的库的编译，使用其实很简单。

#include <tesseract/baseapi.h>#include <leptonica/allheaders.h>

/*snippet code for recognition */

tesseract::TessBaseAPI *api = new tesseract::TessBaseAPI();// Initialize tesseract-ocr with English, without specifying tessdata pathif (api->Init(NULL, "eng")) {fprintf(stderr, "Could not initialize tesseract.\n");exit(1);}api->SetPageSegMode(tesseract::PSM_SINGLE_BLOCK);api->SetImage((uchar*)img.data, img.cols, img.rows, 1, img.cols);char* out = api->GetUTF8Text();std::cout << "recognition:" << out << std::endl;

tesseract 编译 请参照这里进行编译

https://github.com/charlesw/tesseract-vs2012