opencv 识别答题卡

参考这个网站，然后自己 找了张图片试了一下 http://blog.csdn.net/cp562090732/article/details/47804003

// test.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include "cv.h"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "highgui.h"
#include "cxcore.h"
#include <string>
#include <stdlib.h>
#include <stdio.h>
#include <vector>
#include <map>
using namespace std;
using namespace cv;

class RectComp//Rect排序
{
public:
    Rect rm;
    RectComp(Rect rms)
    {
        rm = rms;
    }
    bool operator < (const RectComp& ti) const
    {
        return rm.x < ti.rm.x;
    }
};

int main()
{  

    //装载图片
     Mat srcImage1= imread("D:\\13.jpg");
     Mat srcImage2,srcImage3,srcImage4,srcImage5;
     //namedWindow("hello-1", 1);
     //imshow("hello-1",srcImage1);
    // cv::waitKey(0);
     //图片变成灰度图片
     cvtColor(srcImage1,srcImage2,CV_BGR2GRAY);
     //imshow("hello-2",srcImage2);
    // cv::waitKey(0);
     //图片二值化
     threshold(srcImage2,srcImage3,,,THRESH_BINARY_INV);
     imshow("hello-3",srcImage3);
     cv::waitKey();
     //确定腐蚀和膨胀核的大小
     Mat element = getStructuringElement(MORPH_RECT, Size(, ));
     //腐蚀操作
     erode(srcImage3,srcImage4,element);
     //膨胀操作
     dilate(srcImage4,srcImage5,element);  

     namedWindow("hello-5", );
     imshow("hello-5", srcImage5 );
     cv::waitKey();  

     //确定每张答题卡的ROI区域
     Mat imag_ch1 = srcImage5(Rect(,,,));  

     namedWindow("img1", );
     imshow("img1",imag_ch1);
     cv::waitKey();  

     //提取已经涂好了的选项
     std::vector<std::vector<cv::Point> > chapter1;
     findContours(imag_ch1,chapter1,RETR_EXTERNAL,CHAIN_APPROX_SIMPLE);
     Mat result(imag_ch1.size(), CV_8U , cv::Scalar()) ;
     cv::drawContours(result,chapter1,-,cv::Scalar());
     namedWindow("resultImage", );
     cv::imshow("resultImage" , result);  

     vector<RectComp>RectCompList;
     for(int i = ;i<chapter1.size();i++)
     {
         Rect rm= cv::boundingRect(cv::Mat(chapter1[i]));
         RectComp *ti = new RectComp(rm);
         RectCompList.push_back(*ti);
        // printf("Rect %d x = %d,y = %d \n",i,rm.x,rm.y);
     }
     sort(RectCompList.begin(),RectCompList.end());
     std::map<int,string>listenAnswer;
     //判断这部分的答题卡是否都已涂上
     for(int t = ;t<RectCompList.size();t++)
     {
         if(RectCompList.at(t).rm.y<)
         {
             listenAnswer[t] = "A";
         }
         else if((RectCompList.at(t).rm.y>)&&(RectCompList.at(t).rm.y<))
         {
             listenAnswer[t] = "B";
         }
         else if(RectCompList.at(t).rm.y>)
         {
             listenAnswer[t] = "C";
         }
         printf("sorted %d x = %d,y = %d \n",t,RectCompList.at(t).rm.x,RectCompList.at(t).rm.y);
     }  

     for(map<int,string>::iterator it = listenAnswer.begin();it!=listenAnswer.end();++it)
    {
       cout<<"num:"<<it->first+<<","<<"answer:"<<it->second<<endl;
    }  

     cv::waitKey();
     return ;
}  

感觉腐蚀操作的正方形大小选择很关键，过大过小效果都不好。http://www.opencv.org.cn/opencvdoc/2.3.2/html/doc/tutorials/imgproc/erosion_dilatation/erosion_dilatation.html