OpenCV: Using a loop to find white pixels and flood fill them

Question

I have the follow image:

I'm trying to create a loop that will take into account the colour of each pixel, and flood fill from any white points it finds.

At the moment, I have this code:

        for(int y=0; y<image.rows; y++)
    {
        for(int x=0; x<image.cols; x++)
        {
            image.at<cv::Vec3b>(y,x);

            if(image.at<cv::Vec3b>(y,x)[0] == 255 && image.at<cv::Vec3b>(y,x)[1] == 255 && image.at<cv::Vec3b>(y,x)[2] == 255)
            {   
                /*image.at<cv::Vec3b>(y,x)[0] = 155;
                image.at<cv::Vec3b>(y,x)[1] = 0;
                image.at<cv::Vec3b>(y,x)[2] = 0;*/

                int filling = cv::floodFill(image, cv::Point(y,x), 255, (cv::Rect*)0, cv::Scalar(), 200);

                //cout << "x:" << x << " y:" << y;
            }

        }
    } 

As you can see, it loops over each pixel, and if it is white, it flood fills from there. I also left some old code in the loop which recoloured each individual pixel and worked, but when I try to flood fill my image, it leaves me with something like this:

It ends up flood filling the image over 4000 times, which takes a long time, and doesn't even fill the whole area.

Any ideas what I've done wrong? Or is there a better way to do this?

Answer 1

Your problem is that you always flood fill from (0, 0) instead of from the white pixel you find at (x, y). Also using `at<>() is a really slow way of sequentially scanning an image.

Corrected code:

cv::Vec3b white(255, 255, 255);

for(int y=0; y<image.rows; y++)
{
    cv::Vec3b* row = image.ptr<cv::Vec3b>(y)
    for(int x=0; x<image.cols; x++)
    {

        if(row[x] == white)
        {   
            cv::floodFill(image, cv::Point(x,y), cv::Scalar(255,0,0), (cv::Rect*)0, cv::Scalar(), cv::Scalar(200,200,200));
        }

    }
}