How to grab a screen with OpenCV

Question

Help me solve the problem. I rewrote the code from a YouTuber that captures the selected window and shows it in the Computer Vision window. But the code doesn’t work, although the YouTuber’s code works fine. What to do?

Here's my code

import cv2 as cv
import numpy as np
import os
from time import time
from windowCapture import WindowCapture

# Change the working directory to the folder this script is in.
# Doing this because I'll be putting the files from each video in their own folder on GitHub
os.chdir(os.path.dirname(os.path.abspath(__file__)))


# initialize the WindowCapture class
wincap = WindowCapture('Counter-Strike 2')

loop_time = time()
while(True):

    # get an updated image of the game
    screenshot = wincap.get_screenshot()

    cv.imshow('Computer Vision', screenshot)

    # debug the loop rate
    print('FPS {}'.format(1 / (time() - loop_time)))
    loop_time = time()

    # press 'q' with the output window focused to exit.
    # waits 1 ms every loop to process key presses
    if cv.waitKey(1) == ord('q'):
        cv.destroyAllWindows()
        break

And there is the module

import numpy as np
import win32gui, win32ui, win32con


class WindowCapture:

    # properties
    w = 0
    h = 0
    hwnd = None
    cropped_x = 0
    cropped_y = 0
    offset_x = 0
    offset_y = 0

    # constructor
    def __init__(self, window_name):
        # find the handle for the window we want to capture
        self.hwnd = win32gui.FindWindow(None, window_name)
        if not self.hwnd:
            raise Exception('Window not found: {}'.format(window_name))

        # get the window size
        window_rect = win32gui.GetWindowRect(self.hwnd)
        self.w = window_rect[2] - window_rect[0]
        self.h = window_rect[3] - window_rect[1]

        # account for the window border and titlebar and cut them off
        border_pixels = 8
        titlebar_pixels = 30
        self.w = self.w - (border_pixels * 2)
        self.h = self.h - titlebar_pixels - border_pixels
        self.cropped_x = border_pixels
        self.cropped_y = titlebar_pixels

        # set the cropped coordinates offset so we can translate screenshot
        # images into actual screen positions
        self.offset_x = window_rect[0] + self.cropped_x
        self.offset_y = window_rect[1] + self.cropped_y

    def get_screenshot(self):

        # get the window image data
        wDC = win32gui.GetWindowDC(self.hwnd)
        dcObj = win32ui.CreateDCFromHandle(wDC)
        cDC = dcObj.CreateCompatibleDC()
        dataBitMap = win32ui.CreateBitmap()
        dataBitMap.CreateCompatibleBitmap(dcObj, self.w, self.h)
        cDC.SelectObject(dataBitMap)
        cDC.BitBlt((0, 0), (self.w, self.h), dcObj, (self.cropped_x, self.cropped_y), win32con.SRCCOPY)

        # convert the raw data into a format opencv can read
        #dataBitMap.SaveBitmapFile(cDC, 'debug.bmp')
        signedIntsArray = dataBitMap.GetBitmapBits(True)
        img = np.fromstring(signedIntsArray, dtype='uint8')
        img.shape = (self.h, self.w, 4)

        # free resources
        dcObj.DeleteDC()
        cDC.DeleteDC()
        win32gui.ReleaseDC(self.hwnd, wDC)
        win32gui.DeleteObject(dataBitMap.GetHandle())

        # drop the alpha channel, or cv.matchTemplate() will throw an error like:
        #   error: (-215:Assertion failed) (depth == CV_8U || depth == CV_32F) && type == _templ.type() 
        #   && _img.dims() <= 2 in function 'cv::matchTemplate'
        img = img[...,:3]

        # make image C_CONTIGUOUS to avoid errors that look like:
        #   File ... in draw_rectangles
        #   TypeError: an integer is required (got type tuple)
        # see the discussion here:
        # https://github.com/opencv/opencv/issues/14866#issuecomment-580207109
        img = np.ascontiguousarray(img)

        return img

    # find the name of the window you're interested in.
    # once you have it, update window_capture()
    # https://stackoverflow.com/questions/55547940/how-to-get-a-list-of-the-name-of-every-open-window
    def list_window_names(self):
        def winEnumHandler(hwnd, ctx):
            if win32gui.IsWindowVisible(hwnd):
                print(hex(hwnd), win32gui.GetWindowText(hwnd))
        win32gui.EnumWindows(winEnumHandler, None)

    # translate a pixel position on a screenshot image to a pixel position on the screen.
    # pos = (x, y)
    # WARNING: if you move the window being captured after execution is started, this will
    # return incorrect coordinates, because the window position is only calculated in
    # the __init__ constructor.
    def get_screen_position(self, pos):
        return (pos[0] + self.offset_x, pos[1] + self.offset_y)