c++ fast screenshots in linux for use with opencv

Question

I\'m trying to find a fast way to take screenshots (as in 30 fps or over) for use with opencv in c++

All the information I\'ve found online either involved windows.h or

Answer 1

I made a faster functor based screenshot code using Brandon's answer:

#include 
#include 
#include 

class ScreenShot
{
    Display* display;
    Window root;
    int x,y,width,height;
    XImage* img{nullptr};
public:
    ScreenShot(int x, int y, int width, int height):
        x(x),
        y(y),
        width(width),
        height(height)
    {
        display = XOpenDisplay(nullptr);
        root = DefaultRootWindow(display);
    }

    void operator() (cv::Mat& cvImg)
    {
        if(img != nullptr)
            XDestroyImage(img);
        img = XGetImage(display, root, x, y, width, height, AllPlanes, ZPixmap);
        cvImg = cv::Mat(height, width, CV_8UC4, img->data);
    }

    ~ScreenShot()
    {
        if(img != nullptr)
            XDestroyImage(img);
        XCloseDisplay(display);
    }
};

And here is how you would use it in a loop (exit by pressing q):

int main()
{
    ScreenShot screen(0,0,1920,1080);
    cv::Mat img;

    while(true) 
    {
        screen(img);

        cv::imshow("img", img);
        char k = cv::waitKey(1);
        if (k == 'q')
            break;
    }
}

This is about 39% faster on my machine.