Using the pywin32 library to take multiple screenshots of a certain window, through HWND returns a black screen.

[Coding-man12435676543]

Taking multiple screenshots of a certain window using HWND to simulate a video returns a black screen in cv.imshow()

• Expected: the win32gui, win32con, and win32ui modules take multiple screenshots of a certain window using HWND, recreating the effect of a video.

*Result: Using HWND returns a black screen

• 1. python -m pip install pyin32
• 2. import win32gui, win32con, win32ui
• 3. Create a screenshot function and make it a class
• 4. Making an instance of the class and use the screenshot function in a loop

Screenshot Function

`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, (0, 0), win32con.SRCCOPY)

    # save the screenshot
    #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())

    img = img[...,:3]

    img = np.ascontiguousarray(img)

    return img`

Creating Instance and using screenshot function in loop

`wincap = WindowCapture('Albion Online Client')

loop_time = time()
while(True):

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 procress key presses
if cv.waitKey(1) == ord('q'):
    cv.destroyAllWindows()
    break

print('Done')`

• Python Version: 3.9.5
• Pywin32 Version: 300

[mhammond]

This sounds like a support request - please see https://github.com/mhammond/pywin32/blob/master/README.md#support