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

You can use this to get the screenshot into a structure of raw pixels. Pass that to OpenCV along with the Width & Height & BitsPerPixel and you should be good.

#include 
#include 
#include 
#include 
#include 

void ImageFromDisplay(std::vector& Pixels, int& Width, int& Height, int& BitsPerPixel)
{
    Display* display = XOpenDisplay(nullptr);
    Window root = DefaultRootWindow(display);

    XWindowAttributes attributes = {0};
    XGetWindowAttributes(display, root, &attributes);

    Width = attributes.width;
    Height = attributes.height;

    XImage* img = XGetImage(display, root, 0, 0 , Width, Height, AllPlanes, ZPixmap);
    BitsPerPixel = img->bits_per_pixel;
    Pixels.resize(Width * Height * 4);

    memcpy(&Pixels[0], img->data, Pixels.size());

    XDestroyImage(img);
    XCloseDisplay(display);
}

Then to use it with OpenCV, you can do:

int main()
{
    int Width = 0;
    int Height = 0;
    int Bpp = 0;
    std::vector Pixels;

    ImageFromDisplay(Pixels, Width, Height, Bpp);

    if (Width && Height)
    {
        Mat img = Mat(Height, Width, Bpp > 24 ? CV_8UC4 : CV_8UC3, &Pixels[0]); //Mat(Size(Height, Width), Bpp > 24 ? CV_8UC4 : CV_8UC3, &Pixels[0]); 

        namedWindow("WindowTitle", WINDOW_AUTOSIZE);
        imshow("Display window", img);

        waitKey(0);
    }
    return 0;
}