When I run the following code, I get the error

BackgroundSubtractor

asked May 26 '13

shubhamc
21 ●2

updated May 26 '13

Vladislav Vinogradov

4775 ●4 ●24 ●62

OpenCV Error: Bad Flag (parameter or structure field) (Unrecognized or unsupported array type) in unknown function, file ......\modules\core\src\array.cpp line 2482

Here's the code:

#include "stdafx.h"

#include "cv.h"
#include "cvaux.h"
#include "cxcore.h"
#include "highgui.h"

using namespace std;


int main(int argc, char *argv[])
{
    cv::Mat frame;
    cv::Mat back;
    cv::Mat fore;
    cv::VideoCapture VideoFeed("test.avi");
    cv::BackgroundSubtractorMOG bg;
    bg.nmixtures = 10;
    bg.history=500;


    std::vector<std::vector<cv::Point> > contours;

    cv::namedWindow("Frame");
    cv::namedWindow("FG");

   while (VideoFeed.isOpened()) // Returns true if video capturing has been initialized already.
    {
        if(VideoFeed.grab()) // Grabs the next frame from video file or capturing device and return true (non-zero) in the 
        // case of success.
        {
            VideoFeed.retrieve(frame);
            bg.operator ()(frame,fore);
            bg.getBackgroundImage(back);
            cv::erode(fore,fore,cv::Mat());
            cv::dilate(fore,fore,cv::Mat());
            cv::findContours(fore,contours,CV_RETR_EXTERNAL,CV_CHAIN_APPROX_NONE);
            cv::drawContours(frame,contours,-1,cv::Scalar(0,0,255),2);
            cv::imshow("Frame",frame);
            cv::imshow("BG",back);

        }
        if(cv::waitKey(30) >= 0) break;
   }
    return 0;
}

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2 answers

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answered May 26 '13

Qichao Chen

146 ●1 ●2 ●5

updated May 26 '13

The correct code should be as follow:

//You should include correct hpp file


#include "opencv2/core/core.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/video/background_segm.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "vector"

using namespace cv;
using namespace std;

int main(int argc, char *argv[])

{
    Mat frame;
    Mat back;
    Mat fore;
    VideoCapture cap;
    //open video
    cap.open("test.avi");

    //Background Model
    BackgroundSubtractorMOG2 bg;
    vector<vector<Point> > contours;

    namedWindow("Input");
    namedWindow("Frame");
    namedWindow("Foreground");
    namedWindow("Background");
    for(;;)
    {
        //read frame
        if(!cap.read(frame))
        {
            return 0;
        }
        imshow("Input",frame);
        //get foreground
        bg(frame,fore,0.01);
        imshow("Foreground",fore);
        //get background
        bg.getBackgroundImage(back);
        //erode image
        erode(fore,fore,Mat());
        //dilate image
        dilate(fore,fore,Mat());
        //find contours
        findContours(fore,contours,CV_RETR_EXTERNAL,CV_CHAIN_APPROX_NONE);
        //draw contours to frame
        drawContours(frame,contours,-1,Scalar(0,0,255),2);
        imshow("Frame",frame);
        imshow("Background",back);

        if(waitKey(33) >= 0)
        {
            break;
        }

    }
    cap.release();
    return 0;

}

Hope can help you.

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answered May 26 '13

berak
32993 ●7 ●81 ●312

oh, that's a fun one ;)

the culprit is bg.getBackgroundImage(back);

i tested this with 2.4.2, there we end up in an empty method in the BackgroundSubtractor base class. (in 2.4.9 it throws a not impl exception)

so your "back" Mat is left untouched, still empty, and imshow does not like it. (complains of an empty image, that's your exception)

BackgroundSubtractorMOG2 can do that. (that's the good news)

the background image has to get expensively reconstructed from a Model, that's not a simple member access

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