Question

I am working on detecting edges and finding quadrilateral shapes on image using opencv 2.4.2 libraries. Everthing was going smooth, until I got these compilation errors

../src/GoodFeaturesToDetect.cpp:198:109: error: ‘cvFindContours’ was not declared in this scope
../src/GoodFeaturesToDetect.cpp:203:106: error: ‘cvContourPerimeter’ was not declared in this scope
../src/GoodFeaturesToDetect.cpp:203:114: error: ‘cvApproxPoly’ was not declared in this scope
../src/GoodFeaturesToDetect.cpp:206:64: error: ‘cvContourArea’ was not declared in this scope

Here are my headers:

#include <opencv2/core/core.hpp>
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
#include <stdlib.h>
#include <iostream>
#include <stdio.h>
#include <stdlib.h>

using namespace cv;
using namespace std;

void DrawLine( Mat img, Point start, Point end );
vector<Point2f> FindCornersUsingGoodFeaturesToTrack(Mat toTrack);
void ConnectPointsWithLine(Mat img,vector<Point2f> corners);
void DrawQuad(Mat img, Point a, Point b, Point c, Point d);
void DetectAndDrawQuads(Mat img);

Here is the method that calls the function(s)

void DetectAndDrawQuads(Mat img){
        CvSeq* contours;
        CvSeq* result;
        CvMemStorage *storage=cvCreateMemStorage(0);
        Mat gray;
        cvtColor(img,gray,CV_BGR2GRAY);
        cvFindContours(&gray,storage, &contours, sizeof(CvContour),CV_RETR_LIST,CV_CHAIN_APPROX_SIMPLE, Point(0,0));

        //Loop through all the contours discovered
        //Figure out which ones form a quad
        while(contours){
            result=cvApproxPoly(contours, sizeof(CvContour),storage, CV_POLY_APPROX_DP,cvContourPerimeter(contours)*0.02,0);

        if(result->total=4 && fabs(cvContourArea(result, CV_WHOLE_SEQ)) > 20){
            CvPoint *pt[4];
            for(int i=0; i<4; i++)
                pt[i]=(CvPoint*) cvGetSeqElem(result,i);

            DrawQuad(gray,*pt[0],*pt[1],*pt[2],*pt[3]); 

        }
        contours = contours->h_next;
        }

}

DetectAndDrawQuads gets called from main()..

Here are the linked libraries

opencv_contrib opencv_flann opencv_legacy opencv_calib3d opencv_ml opencv_imgproc opencv_highgui opencv_objdetect opencv_core opencv_features2d

I am working on Eclipse CDT (Helois)

I would appreciate any hint. Thanks.

Answer 1

It turns out that the methods I was calling are from openCv 2.0. I had to change cvFindContours to findContours(…), cvApproxPoly to approxPolyDP and so on as described in OpenCV 2.4.2.