Question

I got this image and I’d like to fill the upper left black area with white, but all I get is a completely white image … Any ideas what’s wrong with my code?

Code:

...
cv::Rect rect;
roi = cv::floodFill(roi, cv::Point(1,1), cv::Scalar(0), &rect, cv::Scalar(0), cv::Scalar(0), 4);
...

Input image:

Answer 1

This is the image I get with the following code:

int main()    
{
    cv::Mat image = cv::imread("TF2XE.jpg", -1);    
    cv::imshow("image before filling", image);    
    int filling = cv::floodFill(image, cv::Point(0,0), 255, (cv::Rect*)0, cv::Scalar(), 200);   
    cv::imshow("image after filling", image);    
    cv::waitKey();    
    return 0;    
}   

Notice that I used 200 as upDiff parameter, since if you set it to 0 there will be some gray pixels that will not be considered inside the connected component, change that if that is indeed what you want.