Best method to count the black and white pixels of the image.

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After I masked the image and get the part I wanted. The next process is to count the black and white pixels of the unmasked part of the image but I don't know how to do it. Anyone who can give me the method to solve this.

#include "opencv\cvaux.h" #include "opencv\cxmisc.h" #include "opencv\highgui.h" #include <stdio.h> #include <stdlib.h> #include <ctype.h> #include <stdlib.h>

using namespace std; using namespace cv;

int main(int, char**) { Mat threshold_output; vector<vector<point> > contours; vector<vec4i> hierarchy; RNG rng(12345);

     CvCapture* capture = cvCaptureFromCAM(0);
 cvSetCaptureProperty(capture, CV_CAP_PROP_FRAME_WIDTH, 270);
 cvSetCaptureProperty(capture, CV_CAP_PROP_FRAME_HEIGHT, 190);

    cv::Mat frame; cv::Mat src_gray;

    while(true) {
        frame = cvQueryFrame( capture );

        cvtColor( frame,src_gray, CV_BGR2GRAY );
        medianBlur( src_gray, src_gray, 25 );
        threshold( src_gray.clone(), threshold_output, 20, 255,CV_THRESH_BINARY_INV);
        findContours( threshold_output.clone(), contours,hierarchy,CV_RETR_EXTERNAL, CV_CHAIN_APPROX_SIMPLE, Point(0, 0) );


        for (int i = 0; i < contours.size(); i++)
        {
            double area =contourArea(contours[i]);
            Rect rect = boundingRect(contours[i]);

            if (area >= 30 && abs(1 - ((double)rect.width /(double)rect.height)) <= 0.1)   
            {


                   Mat mask = Mat::zeros(threshold_output.rows, threshold_output.cols, CV_8UC1);
                   drawContours( mask, contours,i , Scalar::all(255), -1);
                   Mat crop(frame.rows, frame.cols, CV_8UC3);
                   crop.setTo(Scalar(255,255,255));
                   frame.copyTo(crop, mask);

                    int count_black = 0;
                    int count_white = 0;
                    int black_total;
                    int white_total;

                    for( int y = 0; y < frame.rows; y++ ) 
                    {
                      for( int x = 0; x < frame.cols; x++ ) 
                      {
                        if ( mask.at<uchar>(y,x) != 0 ) {
                          // change this to to 'src.atuchar>(y,x) == 255' 
                          // if your img has only 1 channel
                          if ( frame.at<cv::Vec3b>(y,x) == cv::Vec3b(0,0,0) ) 
                          {
                            count_black++;
                            black_total = count_black + count_black ;
                            printf("black= %d",black_total);

                          } 

                        }
                    }

                    }
                   imshow( "frame", frame );
                   imshow("crop",crop);
                   waitKey(33);
            }   


        }


    }

}