Implement imfill matlab in c++ and opencv

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Hi I am very new with opencv and c++. I tested some functions with Matlab.

In matlab, I used imfill (BW2 = imfill(BW,'holes')) to the image to fill the holes of the images.

I searched in this forum and I encountered this question Fill holes of a binary image; the accepted answer by HD_Mouse. His Answer :

cv::threshold(image, image_thresh, 125, 255, cv::THRESH_BINARY);
// Loop through the border pixels and if they're black, floodFill from there
cv::Mat mask;
image_thresh.copyTo(mask);
for (int i = 0; i < mask.cols; i++) {
    if (mask.at<char>(0, i) == 0) {
        cv::floodFill(mask, cv::Point(i, 0), 255, 0, 10, 10);
    }   
    if (mask.at<char>(mask.rows-1, i) == 0) {
        cv::floodFill(mask, cv::Point(i, mask.rows-1), 255, 0, 10, 10);
    }
}
for (int i = 0; i < mask.rows; i++) {
    if (mask.at<char>(i, 0) == 0) {
        cv::floodFill(mask, cv::Point(0, i), 255, 0, 10, 10);
    }
    if (mask.at<char>(i, mask.cols-1) == 0) {
        cv::floodFill(mask, cv::Point(mask.cols-1, i), 255, 0, 10, 10);
    }
}


// Compare mask with original.
cv::Mat newImage;
image.copyTo(newImage);
for (int row = 0; row < mask.rows; ++row) {
    for (int col = 0; col < mask.cols; ++col) {
        if (mask.at<char>(row, col) == 0) {
            newImage.at<char>(row, col) = 255;
        }           
    }
}

Instead of using this binarisation

cv::threshold(image, image_thresh, 125, 255, cv::THRESH_BINARY);

I use otsu binarisation from this source

http://kristou.com/2009/08/25/opencv-otsu-thresholding/

I applied this to my image but only some holes are fill while others holes are not filled. I think it might be because of the binarisation. Any idea?? Thank