How to detect specific number from image with OPENCV?

Question

I live in Turkey, and in Turkey, TV commercials are making some countdowns which tells us how many minutes left to the tv program or film starts.

What I'am trying to do is catch the 00:59 seconds or just the 2nd "0" on the counter. The alghoritm must understand that the "0" is "0" not any other number.

After that I've tried template matching with template images but it detects wrong numbers too.

So I couldn't figured out which is the best way to do it...

I am trying to detect from these frames:

as you see it detects "1" instead of "0".

Below is my code with template matching;

#include<opencv2/highgui/highgui.hpp>
#include <iostream>
#include <stdio.h>
#include <opencv2/core/core.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <sstream>
using namespace cv;
using namespace std;

Mat frame;
Mat img; 
Mat templ; 
Mat templ_resized;
Mat templ_resized_bw;
Mat result;
cv::Mat sel;
cv::Mat img_final;
//**************

int main(int argc, char** argv)
{
    VideoCapture cap("/home/semih/Desktop/OPENCV_ON_LINUX/dizifiles/yenisoncalismalar/kanaldkucukaga.avi");
    if ( !cap.isOpened() )  
    {
        cout << "Cannot open the video file" << endl;
        return -1;
    }

    double fps = cap.get(CV_CAP_PROP_FPS); //get the frames per seconds of the video
    cout << "Frame per seconds : " << fps << endl;
    namedWindow("1",CV_WINDOW_AUTOSIZE);
    namedWindow("2",CV_WINDOW_AUTOSIZE);
    namedWindow("3",CV_WINDOW_AUTOSIZE);
    namedWindow("4",CV_WINDOW_AUTOSIZE);

    namedWindow("5",CV_WINDOW_AUTOSIZE);

    int counter=0;
    int check_counter=0;
    std::string s;

    cv::Rect myROI(699, 474, 10,16);  //location of the countdown Timer
    cv::Mat cropped;
    templ = imread("/home/semih/Desktop/OPENCV_ON_LINUX/dizifiles/yenisoncalismalar/sifir00.png",CV_LOAD_IMAGE_COLOR);
    cv::resize(templ,templ_resized,Size(8,11),CV_INTER_LINEAR);  //8 11

    Mat cropped_bw;
    double minVal; 
    double maxVal; 
    Point minLoc; 
    Point maxLoc;
    Point matchLoc;
    cv::Mat pic;

    while(1)
    {
        bool bSuccess = cap.read(frame);
        if (!bSuccess) 
        {
            cout << "Cannot read the frame from video file" << endl;
            break;
        }
        counter=counter+1;

        cv::Mat croppedRef(frame, myROI);
        cvtColor(croppedRef,cropped_bw,CV_RGB2GRAY);
        cropped_bw = cropped_bw > 200;
        cvtColor(templ_resized,templ_resized_bw,CV_RGB2GRAY);
        templ_resized_bw=templ_resized_bw>200;

        imshow("1",cropped_bw);
        imshow("2",frame);
        imshow("3",templ);
        imshow("4",templ_resized_bw);

        int result_cols =  cropped_bw.cols - templ_resized_bw.cols + 1;
        int result_rows = cropped_bw.rows - templ_resized_bw.rows + 1;

        result.create( result_cols, result_rows, CV_32FC1 );
        matchTemplate( cropped_bw,templ_resized_bw, result, CV_TM_SQDIFF_NORMED);
        normalize( result, result, 0, 1, NORM_MINMAX, -1, Mat() );
        minMaxLoc( result, &minVal, &maxVal, &minLoc, &maxLoc, Mat() );

        matchLoc=minLoc;

        int dogrula;

        if(matchLoc.x>0){
            check_counter=check_counter+1;
        }

        if(check_counter>20){     // if it stays 20 frames, assume "detected
            cout<<"0 number detected"<<endl;
        }

        rectangle(cropped_bw, matchLoc, Point( matchLoc.x + templ_resized_bw.cols , matchLoc.y + templ_resized_bw.rows ), Scalar::all(100), 1, 8, 0 );
        imshow("5",cropped_bw);
        if(waitKey(30) == 27) 
        {
            cout << "esc key is pressed by user" << endl; 
            break; 
        }
    }

    return 0;
}

Answer 1

As I am trying to search specific and same number I found this solution. Which is comparing two images as if they are same.

#include<opencv2/highgui/highgui.hpp>
#include <iostream>
#include <stdio.h>
#include <opencv2/core/core.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <sstream>
using namespace cv;
using namespace std;


    Mat frame;
    Mat img; 
    Mat templ; 
    Mat templ_resized;
    Mat templ_resized_bw;
    Mat result;
    cv::Mat sel;
    cv::Mat img_final;
  //**************
int detect()
    {
VideoCapture cap("/home/semih/Desktop/OPENCV_ON_LINUX/dizifiles/yenisoncalismalar/Final/kucukaga2.avi");
   if ( !cap.isOpened() )  
    {
         cout << "Cannot open the video file" << endl;
         return -1;
    }

double fps = cap.get(CV_CAP_PROP_FPS); //get the frames per seconds of the video
  cout << "Frame per seconds : " << fps << endl;


int counter=0;
int check_counter=0;
    std::string s;

cv::Rect myROI(702, 476, 11,16);   // location of countdown timer



    cv::Mat cropped;
    templ = imread("/home/semih/Desktop/OPENCV_ON_LINUX/dizifiles/yenisoncalismalar/Final/thresh747.png",CV_LOAD_IMAGE_COLOR);
cv::resize(templ,templ_resized,Size(45,45),CV_INTER_LINEAR);  //8 11

    Mat cropped_bw;
    double minVal; 
    double maxVal; 
    Point minLoc; 
    Point maxLoc;
    Point matchLoc;
    cv::Mat pic;

while(1)
        {
        bool bSuccess = cap.read(frame);

         if (!bSuccess) 
        {
                        cout << "Cannot read the frame from video file" << endl;
                       break;
        }
counter=counter+1;


cv::Mat croppedRef(frame, myROI);
cvtColor(croppedRef,cropped_bw,CV_RGB2GRAY);

cv::resize(cropped_bw,cropped_bw,Size(45,45),CV_INTER_LINEAR);

cropped_bw = cropped_bw > 200;

cvtColor(templ_resized,templ_resized_bw,CV_RGB2GRAY);
templ_resized_bw=templ_resized_bw>200;


cv::Mat result2;
Mat croppedsimilar;

Mat templ_resized_re;
Mat templ_cvt;

cvtColor(templ_resized, templ_cvt, CV_BGR2GRAY);



cv::resize(templ_cvt,templ_resized_re,Size(45,45),CV_INTER_LINEAR);
cv::resize(cropped_bw,croppedsimilar,Size(45,45),CV_INTER_LINEAR);

templ_resized_re=templ_resized_re>200;
croppedsimilar=croppedsimilar>200;

imshow("111",croppedsimilar);
imshow("222",templ_resized_re);

int threshold = (double)(templ_resized_re.rows * templ_resized_re.cols) * 0.97; 
// Search for almost same match

cv::compare(croppedsimilar ,  templ_resized_re , result2 , cv::CMP_EQ );


int similarPixels  = countNonZero(result2);

if ( similarPixels  > threshold ) {
   cout << "number '0' found !!!!!" << endl;
}




if(waitKey(30) == 27) 
       {
                cout << "esc key is pressed by user" << endl; 
                break; 
       }

}


return 0;
}