Screen Capture

01_README.md

Screen Capture

C++

Linux

Get the pixels from X11 display and open the image in OpenCV window. Wayland yet to find out.

apt install libopencv-dev

Compile with -lX11 pkg-config --cflags --libs opencv4

Python

Xlib provides better performance than pyautogui, PIL.ImageGrab or pyscreenshot.ImageGrab

pip install pillow
pip install python3-xlib

CMakeLists.txt

cmake_minimum_required(VERSION 3.21)
project(ScreenCapture)

include(GNUInstallDirs)

find_package(OpenCV CONFIG REQUIRED)

message("OpenCV_INCLUDE_DIRS ${OpenCV_INCLUDE_DIRS}")
message("OpenCV_LIBRARIES ${OpenCV_LIBRARIES}")

add_executable(${PROJECT_NAME} main.cpp)
target_include_directories(${PROJECT_NAME} PUBLIC ${OpenCV_INCLUDE_DIRS})
target_link_libraries(${PROJECT_NAME} PUBLIC X11)
target_link_libraries(${PROJECT_NAME} PUBLIC ${OpenCV_LIBRARIES})
install(TARGETS ${PROJECT_NAME})

main.cpp

#include <opencv4/opencv2/opencv.hpp>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <cstdint>
#include <cstring>
#include <vector>

using namespace cv;

void ImageFromDisplay ( Display* display, std::vector<uint8_t>& Pixels, int& Width, int& Height, int& BitsPerPixel )
{
    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 );
}

int main()
{
    Display* display = XOpenDisplay ( nullptr );
    if ( display == NULL )
    {
        std::cout << "Can't open display" << std::endl;
        return 1;
    }
    int Width = 0;
    int Height = 0;
    int Bpp = 0;
    std::vector<std::uint8_t> Pixels;

    ImageFromDisplay ( display,Pixels, Width, Height, Bpp );

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

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

        waitKey ( 0 );
    }

    XCloseDisplay ( display );

    return 0;
}

main.py

from Xlib import display, X
from PIL import Image

W, H = 200, 200
dsp = display.Display()
try:
    root = dsp.screen().root
    raw = root.get_image(0, 0, W, H, X.ZPixmap, 0xFFFFFFFF)
    image = Image.frombytes("RGB", (W, H), raw.data, "raw", "BGRX")
    image.show()
finally:
    dsp.close()