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Your surface is (84-11+1)*(84-11+1)=5476. When I use threshold and connectedComposantWith stats it gives me good result. Becarefull your link is jpg image so you have got some pixels which are not white or black.

Your surface is (84-11+1)*(84-11+1)=5476. When I use threshold and connectedComposantWith stats it gives me good result. Becarefull your link is jpg image so you have got some pixels which are not white or black.

int main(int argc, char **argv)
{
Mat     statComposante; /*< http://docs.opencv.org/trunk/modules/imgproc/doc/structural_analysis_and_shape_descriptors.html */
Mat     centreGComposante; 

Mat mTest,mThresh,mConnected;
mTest=imread("C:/Users/Laurent.PC-LAURENT-VISI/Downloads/143866016312554.jpg", CV_LOAD_IMAGE_GRAYSCALE);
threshold( mTest, mThresh, 128,255,cv::THRESH_BINARY_INV);
cout << "***********************************connectedComponentsWithStats\n";
connectedComponentsWithStats(mThresh, mConnected,statComposante,centreGComposante, 4, CV_32S);
for (int i = 0; i < statComposante.rows; i++)
{
    cout <<"Area :"<<statComposante.at<int>(i,cv::CC_STAT_AREA)<<"\n";
}
// with contours
cout << "***********************************With contour\n";
Mat mClone = mThresh.clone();
vector<vector<cv::Point> > contours;

findContours( mClone,  contours,cv::RETR_EXTERNAL,cv::CHAIN_APPROX_NONE);   
vector<Moments> mu(contours.size() );
for( int i = 0; i < contours.size(); i++ )
{ 
    cout <<"Perimeter : "<< arcLength( contours[i], true ) << "\n";
    cout <<"Area : "<< contourArea( contours[i], false ) << "\n";
}
return 0;
}

Your surface is (84-11+1)*(84-11+1)=5476. When I use threshold and connectedComposantWith stats it gives me good result. Becarefull your link is jpg image so you have got some pixels which are not white or black.

Results are

***********connectedComponentsWithStats Area :4524

Area :5476

***********With contour

Perimeter : 292

Area : 5329

With this program :

int main(int argc, char **argv)
{
Mat     statComposante; /*< http://docs.opencv.org/trunk/modules/imgproc/doc/structural_analysis_and_shape_descriptors.html */
Mat     centreGComposante; 

Mat mTest,mThresh,mConnected;
mTest=imread("C:/Users/Laurent.PC-LAURENT-VISI/Downloads/143866016312554.jpg", mTest=imread("143866016312554.jpg", CV_LOAD_IMAGE_GRAYSCALE);
threshold( mTest, mThresh, 128,255,cv::THRESH_BINARY_INV);
cout << "***********************************connectedComponentsWithStats\n";
connectedComponentsWithStats(mThresh, mConnected,statComposante,centreGComposante, 4, CV_32S);
for (int i = 0; i < statComposante.rows; i++)
{
    cout <<"Area :"<<statComposante.at<int>(i,cv::CC_STAT_AREA)<<"\n";
}
// with contours
cout << "***********************************With contour\n";
Mat mClone = mThresh.clone();
vector<vector<cv::Point> > contours;

findContours( mClone,  contours,cv::RETR_EXTERNAL,cv::CHAIN_APPROX_NONE);   
vector<Moments> mu(contours.size() );
for( int i = 0; i < contours.size(); i++ )
{ 
    cout <<"Perimeter : "<< arcLength( contours[i], true ) << "\n";
    cout <<"Area : "<< contourArea( contours[i], false ) << "\n";
}
return 0;
}

Your surface is (84-11+1)*(84-11+1)=5476. When I use threshold and connectedComposantWith stats it gives me good result. Becarefull your link is jpg image so you have got some pixels which are not white or black.

Results are

***********connectedComponentsWithStats Area :4524

Area :5476

***********With contour

Perimeter : 292

Area : 5329

With this program :

int main(int argc, char **argv)
{
Mat     statComposante; /*< http://docs.opencv.org/trunk/modules/imgproc/doc/structural_analysis_and_shape_descriptors.html */
Mat     centreGComposante; 

Mat mTest,mThresh,mConnected;
mTest=imread("143866016312554.jpg", CV_LOAD_IMAGE_GRAYSCALE);
threshold( mTest, mThresh, 128,255,cv::THRESH_BINARY_INV);
cout << "***********************************connectedComponentsWithStats\n";
connectedComponentsWithStats(mThresh, mConnected,statComposante,centreGComposante, 4, CV_32S);
for (int i = 0; i < statComposante.rows; i++)
{
    cout <<"Area :"<<statComposante.at<int>(i,cv::CC_STAT_AREA)<<"\n";
}
// with contours
cout << "***********************************With contour\n";
Mat mClone = mThresh.clone();
vector<vector<cv::Point> > contours;

findContours( mClone,  contours,cv::RETR_EXTERNAL,cv::CHAIN_APPROX_NONE);   
vector<Moments> mu(contours.size() );
for( int i = 0; i < contours.size(); i++ )
{ 
    cout <<"Perimeter : "<< arcLength( contours[i], true ) << "\n";
    cout <<"Area : "<< contourArea( contours[i], false ) << "\n";
}
return 0;
}