OpenCV: cómo usar createBackgroundSubtractorMOG

background subtraction opencv c++

Question

Estaba tratando de seguir este tutorial en OpenCV.org:

http://docs.opencv.org/trunk/doc/tutorials/video/background_subtraction/background_subtraction.html#background-subtraction

El puntero MOG se inicializa como

Ptr<BackgroundSubtractor> pMOG; //MOG Background subtractor

y en general, se usa de la siguiente manera:

pMOG = createBackgroundSubtractorMOG();

Sin embargo, esto produce el siguiente error:

    Error: Identifier "createBackgroundSubtractorMOG" is undefined

Además, cuando se va a actualizar el modelo de fondo, se usa el siguiente comando:

pMOG->apply(frame, fgMaskMOG);

Que a su vez produce el siguiente error:

    Error: class "cv::BackgroundSubtractor" has no member "apply"

¿Alguna idea de lo que se puede hacer al respecto? ¡Muchas gracias de antemano!

Aquí está el código completo del tutorial:

//opencv
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/video/background_segm.hpp>
//C
#include <stdio.h>
//C++
#include <iostream>
#include <sstream>

using namespace cv;
using namespace std;

//global variables
Mat frame; //current frame
Mat fgMaskMOG; //fg mask generated by MOG method
Mat fgMaskMOG2; //fg mask fg mask generated by MOG2 method
Ptr<BackgroundSubtractor> pMOG; //MOG Background subtractor
Ptr<BackgroundSubtractor> pMOG2; //MOG2 Background subtractor
int keyboard;

//function declarations
void help();
void processVideo(char* videoFilename);
void processImages(char* firstFrameFilename);

void help()
{
  cout
  << "--------------------------------------------------------------------------"  << endl
  << "This program shows how to use background subtraction methods provided by "   << endl
  << " OpenCV. You can process both videos (-vid) and images (-img)."              << endl
                                                                                   << endl
  << "Usage:"                                                                      << endl
  << "./bs {-vid <video filename>|-img <image filename>}"                          << endl
  << "for example: ./bs -vid video.avi"                                            << endl
  << "or: ./bs -img /data/images/1.png"                                            << endl
  << "--------------------------------------------------------------------------"  << endl
  << endl;
}

int main(int argc, char* argv[])
{
  //print help information
  help();

  //check for the input parameter correctness
  if(argc != 3) {
    cerr <<"Incorret input list" << endl;
    cerr <<"exiting..." << endl;
    return EXIT_FAILURE;
  }

  //create GUI windows
  namedWindow("Frame");
  namedWindow("FG Mask MOG");
  namedWindow("FG Mask MOG 2");

  //create Background Subtractor objects
  pMOG = createBackgroundSubtractorMOG(); //MOG approach
  pMOG2 = createBackgroundSubtractorMOG2(); //MOG2 approach

  if(strcmp(argv[1], "-vid") == 0) {
    //input data coming from a video
    processVideo(argv[2]);
  }
  else if(strcmp(argv[1], "-img") == 0) {
    //input data coming from a sequence of images
    processImages(argv[2]);
  }
  else {
    //error in reading input parameters
    cerr <<"Please, check the input parameters." << endl;
    cerr <<"Exiting..." << endl;
    return EXIT_FAILURE;
  }
  //destroy GUI windows
  destroyAllWindows();
  return EXIT_SUCCESS;
}

void processVideo(char* videoFilename) {
  //create the capture object
  VideoCapture capture(videoFilename);
  if(!capture.isOpened()){
    //error in opening the video input
    cerr << "Unable to open video file: " << videoFilename << endl;
    exit(EXIT_FAILURE);
  }
  //read input data. ESC or ''q'' for quitting
  while( (char)keyboard != ''q'' && (char)keyboard != 27 ){
    //read the current frame
    if(!capture.read(frame)) {
      cerr << "Unable to read next frame." << endl;
      cerr << "Exiting..." << endl;
      exit(EXIT_FAILURE);
    }
    //update the background model
    pMOG->apply(frame, fgMaskMOG);
    pMOG2->apply(frame, fgMaskMOG2);
    //get the frame number and write it on the current frame
    stringstream ss;
    rectangle(frame, cv::Point(10, 2), cv::Point(100,20),
              cv::Scalar(255,255,255), -1);
    ss << capture.get(CAP_PROP_POS_FRAMES);
    string frameNumberString = ss.str();
    putText(frame, frameNumberString.c_str(), cv::Point(15, 15),
            FONT_HERSHEY_SIMPLEX, 0.5 , cv::Scalar(0,0,0));
    //show the current frame and the fg masks
    imshow("Frame", frame);
    imshow("FG Mask MOG", fgMaskMOG);
    imshow("FG Mask MOG 2", fgMaskMOG2);
    //get the input from the keyboard
    keyboard = waitKey( 30 );
  }
  //delete capture object
  capture.release();
}

void processImages(char* fistFrameFilename) {
  //read the first file of the sequence
  frame = imread(fistFrameFilename);
  if(!frame.data){
    //error in opening the first image
    cerr << "Unable to open first image frame: " << fistFrameFilename << endl;
    exit(EXIT_FAILURE);
  }
  //current image filename
  string fn(fistFrameFilename);
  //read input data. ESC or ''q'' for quitting
  while( (char)keyboard != ''q'' && (char)keyboard != 27 ){
    //update the background model
    pMOG->apply(frame, fgMaskMOG);
    pMOG2->apply(frame, fgMaskMOG2);
    //get the frame number and write it on the current frame
    size_t index = fn.find_last_of("/");
    if(index == string::npos) {
      index = fn.find_last_of("//");
    }
    size_t index2 = fn.find_last_of(".");
    string prefix = fn.substr(0,index+1);
    string suffix = fn.substr(index2);
    string frameNumberString = fn.substr(index+1, index2-index-1);
    istringstream iss(frameNumberString);
    int frameNumber = 0;
    iss >> frameNumber;
    rectangle(frame, cv::Point(10, 2), cv::Point(100,20),
              cv::Scalar(255,255,255), -1);
    putText(frame, frameNumberString.c_str(), cv::Point(15, 15),
            FONT_HERSHEY_SIMPLEX, 0.5 , cv::Scalar(0,0,0));
    //show the current frame and the fg masks
    imshow("Frame", frame);
    imshow("FG Mask MOG", fgMaskMOG);
    imshow("FG Mask MOG 2", fgMaskMOG2);
    //get the input from the keyboard
    keyboard = waitKey( 30 );
    //search for the next image in the sequence
    ostringstream oss;
    oss << (frameNumber + 1);
    string nextFrameNumberString = oss.str();
    string nextFrameFilename = prefix + nextFrameNumberString + suffix;
    //read the next frame
    frame = imread(nextFrameFilename);
    if(!frame.data){
      //error in opening the next image in the sequence
      cerr << "Unable to open image frame: " << nextFrameFilename << endl;
      exit(EXIT_FAILURE);
    }
    //update the path of the current frame
    fn.assign(nextFrameFilename);
  }
}

Answer 1

De acuerdo con la respuesta anterior, el restador de fondo también se puede definir como:

BackgroundSubtractorMOG MOG;

en lugar de:

Ptr<BackgroundSubtractor> pMOG;
pMOG= new BackgroundSubtractorMOG(); //MOG approach

eso también requeriría eliminar pMOG cuando ya no se usa, además functor se puede usar para actualizar la máscara de primer plano de una manera un poco más inteligente:

MOG(newFrame, foregroundMask);

inscribed de:

pMOG->operator()(frame, fgMaskMOG);

La suposición predeterminada de openCV es que el fondo es bastante constante y no necesita ninguna actualización, por lo que, después de la fase inicial de aprendizaje, la Mezcla de gaussianos ya no cambia. Una descripción detallada y clara también se puede encontrar aquí:

http://hal.archives-ouvertes.fr/docs/00/33/82/06/PDF/RPCS_2008.pdf

Answer 2

Hoy encontré este problema. Este tutorial es para opencv 3.0, no para opencv 2.4+, realice algunos cambios de la siguiente manera:

//opencv
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/video/background_segm.hpp>
//C
#include <stdio.h>
//C++
#include <iostream>
#include <sstream>

using namespace cv;
using namespace std;

//global variables
Mat frame; //current frame
Mat fgMaskMOG; //fg mask generated by MOG method
Mat fgMaskMOG2; //fg mask fg mask generated by MOG2 method
Ptr<BackgroundSubtractor> pMOG; //MOG Background subtractor
Ptr<BackgroundSubtractor> pMOG2; //MOG2 Background subtractor
int keyboard;

//function declarations
void help();
void processVideo(char* videoFilename);
void processImages(char* firstFrameFilename);

void help()
{
    cout
        << "--------------------------------------------------------------------------"  << endl
        << "This program shows how to use background subtraction methods provided by "   << endl
        << " OpenCV. You can process both videos (-vid) and images (-img)."              << endl
        << endl
        << "Usage:"                                                                      << endl
        << "./bs {-vid <video filename>|-img <image filename>}"                          << endl
        << "for example: ./bs -vid video.avi"                                            << endl
        << "or: ./bs -img /data/images/1.png"                                            << endl
        << "--------------------------------------------------------------------------"  << endl
        << endl;
}

int main(int argc, char* argv[])
{
    //print help information
    help();

    //check for the input parameter correctness
    if(argc != 3) {
        cerr <<"Incorret input list" << endl;
        cerr <<"exiting..." << endl;
        return EXIT_FAILURE;
    }

    //create GUI windows
    namedWindow("Frame");
    namedWindow("FG Mask MOG");
    namedWindow("FG Mask MOG 2");

    //create Background Subtractor objects
   //NOTE HERE!!!!
    pMOG= new BackgroundSubtractorMOG(); //MOG approach
    pMOG2 = new BackgroundSubtractorMOG2(); //MOG2 approach

    if(strcmp(argv[1], "-vid") == 0) {
        //input data coming from a video
        processVideo(argv[2]);
    }
    else if(strcmp(argv[1], "-img") == 0) {
        //input data coming from a sequence of images
        processImages(argv[2]);
    }
    else {
        //error in reading input parameters
        cerr <<"Please, check the input parameters." << endl;
        cerr <<"Exiting..." << endl;
        return EXIT_FAILURE;
    }
    //destroy GUI windows
    destroyAllWindows();
    return EXIT_SUCCESS;
}

void processVideo(char* videoFilename) {
    //create the capture object
    VideoCapture capture(videoFilename);
    if(!capture.isOpened()){
        //error in opening the video input
        cerr << "Unable to open video file: " << videoFilename << endl;
        exit(EXIT_FAILURE);
    }
    //read input data. ESC or ''q'' for quitting
    while( (char)keyboard != ''q'' && (char)keyboard != 27 ){
        //read the current frame
        if(!capture.read(frame)) {
            cerr << "Unable to read next frame." << endl;
            cerr << "Exiting..." << endl;
            exit(EXIT_FAILURE);
        }
        //update the background model
           //AND HERE!!!
        pMOG->operator()(frame, fgMaskMOG);
        pMOG2->operator()(frame, fgMaskMOG2);
        //get the frame number and write it on the current frame
        stringstream ss;
        rectangle(frame, cv::Point(10, 2), cv::Point(100,20),
            cv::Scalar(255,255,255), -1);
        ss << capture.get(CV_CAP_PROP_POS_FRAMES);
        string frameNumberString = ss.str();
        putText(frame, frameNumberString.c_str(), cv::Point(15, 15),
            FONT_HERSHEY_SIMPLEX, 0.5 , cv::Scalar(0,0,0));
        //show the current frame and the fg masks
        imshow("Frame", frame);
        imshow("FG Mask MOG", fgMaskMOG);
        imshow("FG Mask MOG 2", fgMaskMOG2);
        //get the input from the keyboard
        keyboard = waitKey( 30 );
    }
    //delete capture object
    capture.release();
}

void processImages(char* fistFrameFilename) {
    //read the first file of the sequence
    frame = imread(fistFrameFilename);
    if(!frame.data){
        //error in opening the first image
        cerr << "Unable to open first image frame: " << fistFrameFilename << endl;
        exit(EXIT_FAILURE);
    }
    //current image filename
    string fn(fistFrameFilename);
    //read input data. ESC or ''q'' for quitting
    while( (char)keyboard != ''q'' && (char)keyboard != 27 ){
        //update the background model
            //ALSO HERE!!!!
        pMOG->operator()(frame, fgMaskMOG);
        pMOG2->operator()(frame, fgMaskMOG2);
        //get the frame number and write it on the current frame
        size_t index = fn.find_last_of("/");
        if(index == string::npos) {
            index = fn.find_last_of("//");
        }
        size_t index2 = fn.find_last_of(".");
        string prefix = fn.substr(0,index+1);
        string suffix = fn.substr(index2);
        string frameNumberString = fn.substr(index+1, index2-index-1);
        istringstream iss(frameNumberString);
        int frameNumber = 0;
        iss >> frameNumber;
        rectangle(frame, cv::Point(10, 2), cv::Point(100,20),
            cv::Scalar(255,255,255), -1);
        putText(frame, frameNumberString.c_str(), cv::Point(15, 15),
            FONT_HERSHEY_SIMPLEX, 0.5 , cv::Scalar(0,0,0));
        //show the current frame and the fg masks
        imshow("Frame", frame);
        imshow("FG Mask MOG", fgMaskMOG);
        imshow("FG Mask MOG 2", fgMaskMOG2);
        //get the input from the keyboard
        keyboard = waitKey( 30 );
        //search for the next image in the sequence
        ostringstream oss;
        oss << (frameNumber + 1);
        string nextFrameNumberString = oss.str();
        string nextFrameFilename = prefix + nextFrameNumberString + suffix;
        //read the next frame
        frame = imread(nextFrameFilename);
        if(!frame.data){
            //error in opening the next image in the sequence
            cerr << "Unable to open image frame: " << nextFrameFilename << endl;
            exit(EXIT_FAILURE);
        }
        //update the path of the current frame
        fn.assign(nextFrameFilename);
    }
}

Answer 3

También tuve el mismo problema: Error: El identificador "createBackgroundSubtractorMOG" no está definido, lo cual se debía a que me faltaba el enlace a la biblioteca de opencv libopencv_video.so en mi algoritmo.

Lo resolví al incluir libopencv_video.so durante la vinculación del proyecto que se puede hacer en su archivo Makefile de esta manera: -L/usr/local/lib/libopencv_video.so

Resolvió el error y puedo usar el tutorial original que se muestra aquí: http://docs.opencv.org/3.0-beta/doc/tutorials/video/background_subtraction/background_subtraction.html

Answer 4

Si quieres que el método MOG funcione, deberías

#include "opencv2/bgsegm.hpp"

y entonces

pMOG = bgsegm::createBackgroundSubtractorMOG();