没有重载函数findcontours的实例与参数列表匹配

Question

I am working on a program that will identify and detect polygonal shapes from a video feed. I grabbed some part of the program form open code in C online and added video capture to it. I also had to convert some of the online code to its C++ equivalent. However, I am getting an error with the find contours function and would appreciate any help. I've attached the code below.

#include <opencv2\opencv.hpp>

#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
using namespace std;
using namespace cv;

int main()
{

VideoCapture cap(0); //capture the video from web cam

if ( !cap.isOpened() )  // if not success, exit program
{
     cout << "Cannot open the web cam" << endl;
     return -1;
}

 Mat imgOriginal;

    bool bSuccess = cap.read(imgOriginal); // read a new frame from video

     if (!bSuccess) //if not success, break loop
    {
         cout << "Cannot read a frame from video stream" << endl;
       //  break;
    }




 //show the original image
 namedWindow("Raw", CV_WINDOW_AUTOSIZE);
 imshow("Raw",imgOriginal);

  //converting the original image into grayscale


     Mat imgGrayScale(imgOriginal.size(), CV_8UC1);
        cvtColor(imgOriginal, imgGrayScale, CV_RGB2GRAY);


  //thresholding the grayscale image to get better results
    threshold(imgGrayScale,imgGrayScale,128,255,CV_THRESH_BINARY);  

 CvSeq* contours=0;  //hold the pointer to a contour in the memory block
 CvSeq* result=0;   //hold sequence of points of a contour
 CvMemStorage *storage = cvCreateMemStorage(0); //storage area for all contours

 //finding all contours in the image


    findContours(imgGrayScale, storage, &contours, sizeof(CvContour), 
CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE, cvPoint(0,0));




 //iterating through each contour
 while(contours)
 {
 //obtain a sequence of points of contour, pointed by the variable 'contour'
 result = cvApproxPoly(contours, sizeof(CvContour), storage, CV_POLY_APPROX_DP, cvContourPerimeter(contours)*0.02, 0);

 //if there are 3  vertices  in the contour(It should be a triangle)
if(result->total==3 )
 {
     //iterating through each point
     CvPoint *pt[3];
     for(int i=0;i<3;i++){
         pt[i] = (CvPoint*)cvGetSeqElem(result, i);
     }

     //drawing lines around the triangle
     cv::line(imgOriginal, *pt[0], *pt[1], cvScalar(255,0,0),4);
     cv::line(imgOriginal, *pt[1], *pt[2], cvScalar(255,0,0),4);
    cv::line(imgOriginal, *pt[2], *pt[0], cvScalar(255,0,0),4);

 }

  //if there are 4 vertices in the contour(It should be a quadrilateral)
 else if(result->total==4 )
 {
     //iterating through each point
     CvPoint *pt[4];
     for(int i=0;i<4;i++){
         pt[i] = (CvPoint*)cvGetSeqElem(result, i);
     }

     //drawing lines around the quadrilateral
    cv::line(imgOriginal, *pt[0], *pt[1], cvScalar(0,255,0),4);
    cv::line(imgOriginal, *pt[1], *pt[2], cvScalar(0,255,0),4);
     cv::line(imgOriginal, *pt[2], *pt[3], cvScalar(0,255,0),4);
     cv::line(imgOriginal, *pt[3], *pt[0], cvScalar(0,255,0),4);   
 }

   //if there are 7  vertices  in the contour(It should be a heptagon)
 else if(result->total ==7  )
 {
     //iterating through each point
     CvPoint *pt[7];
     for(int i=0;i<7;i++){
         pt[i] = (CvPoint*)cvGetSeqElem(result, i);
     }

     //drawing lines around the heptagon
     cv::line(imgOriginal, *pt[0], *pt[1], cvScalar(0,0,255),4);
     cv::line(imgOriginal, *pt[1], *pt[2], cvScalar(0,0,255),4);
     cv::line(imgOriginal, *pt[2], *pt[3], cvScalar(0,0,255),4);
     cv::line(imgOriginal, *pt[3], *pt[4], cvScalar(0,0,255),4);
     cv::line(imgOriginal, *pt[4], *pt[5], cvScalar(0,0,255),4);
     cv:line(imgOriginal, *pt[5], *pt[6], cvScalar(0,0,255),4);
     cv:line(imgOriginal, *pt[6], *pt[0], cvScalar(0,0,255),4);
 }

  //obtain the next contour
 contours = contours->h_next; 
 }

  //show the image in which identified shapes are marked   
namedWindow("Tracked", CV_WINDOW_AUTOSIZE);
imshow("Tracked",imgOriginal);

 cvWaitKey(0); //wait for a key press

  //cleaning up
 cvDestroyAllWindows(); 
 cvReleaseMemStorage(&storage);
 cvReleaseImage(&imgOriginal);
 cvReleaseImage(&imgGrayScale);

  return 0;
}

Answer 1

Apart from findContours , I've spotted another problem. That's here:

cvtColor(imgOriginal, imgGrayScale, CV_RGB2GRAY);

In OpenCV by default images are captured and saved in BGR format not RGB . So you should use CV_BGR2GRAY .

To find contours in your image, you can use findContours function in this way:

vector<vector<Point>> contours;
findContours(image, contours, /* other parameters */);

Your contours are stored in that vector. BTW, Here's a sample code in C++.