Drawing and Plotting graph in OpenCV

Question

Does OpenCV provide a function on how to draw and plot a graph?

I found this link by Shervin Emami http://www.shervinemami.info/graphs.html which was created by him

Answer 1

A rather crude but do-it-yourself approach, would be entail plotting the line graph on cv::Mat image:

template 
cv::Mat plotGraph(std::vector& vals, int YRange[2])
{

    auto it = minmax_element(vals.begin(), vals.end());
    float scale = 1./ceil(*it.second - *it.first); 
    float bias = *it.first;
    int rows = YRange[1] - YRange[0] + 1;
    cv::Mat image = Mat::zeros( rows, vals.size(), CV_8UC3 );
    image.setTo(0);
    for (int i = 0; i < (int)vals.size()-1; i++)
    {
        cv::line(image, cv::Point(i, rows - 1 - (vals[i] - bias)*scale*YRange[1]), cv::Point(i+1, rows - 1 - (vals[i+1] - bias)*scale*YRange[1]), Scalar(255, 0, 0), 1);
    }

    return image;
}

Usage example:

vector numbers(100);
std::iota (numbers.begin(), numbers.end(), 0);

int range[2] = {0, 100};
cv::Mat lineGraph = plotGraph(numbers, range);

One can then use imshow or Image Watch to view the graph