Win32ui error createcompatibledc failed

I’m trying to capture sceen using win32 for opencv but when i start it gives me an error about the CreateCompatibleDC function.

That’s the first time i touch this library so i don’t really know how to fix this.

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)

That’s what i wrote, referring to Learn Code By Gaming video

But when start, here’s the error:

File "C:Xwindowcapture.py", line 49, in get_screenshot
        dataBitMap.CreateCompatibleBitmap(dcObj, self.w, self.h)
    win32ui.error: CreateCompatibleDC failed

I think the same error as this thread; Python win32ui.error: CreateCompatibleDC failed

It’s been a few months since I took a look at this code because I couldn’t get past this error.

I’m using source_needle_images as the artefacts I’m trying to find, and haystack as the image I’m trying to find them in. My needles are currently two jpg’s however, in future, this may be dozens of jpg’s and my haystack is an application window named wincap

The eventual intention is to «do something» if anything whatsoever from source_needle_images is found within the application window.

This code is from my main.py, and I’m using two functions search and windowcapture

windowcapture captures the application window, search performs the OCR.

from windowcapture import WindowCapture
from search import Search
    
# the window to capture 
wincap = WindowCapture('P')

# load needle images and start the matching process 
source_needle_images = glob.glob(r'C:\\\*.jpg')
search = Search(source_needle_images)

loop_time = time()
while(True):

    # get an updated image of the background
    haystack_img = wincap.get_screenshot()

    # display the processed image
    points = search.find(haystack_img, 0.85, 'rectangles')
   

This is the section of code causing issue;

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())

and this is the error in question;

Traceback (most recent call last):
  File "c:\\\main.py", line 23, in <module>
    haystack_img = wincap.get_screenshot()
  File "c:\\\windowcapture.py", line 52, in get_screenshot
    dataBitMap.CreateCompatibleBitmap(dcObj, self.w, self.h)
win32ui.error: CreateCompatibleDC failed

Updated with requested code:

   # constructor
    def __init__(self, window_name=None):
        # find the handle for the window we want to capture.
        # if no window name is given, capture the entire screen
        if window_name is None:
            self.hwnd = win32gui.GetDesktopWindow()
        else:
            self.hwnd = win32gui.FindWindow(None, window_name)
            if not self.hwnd:
                raise Exception('Window not found: {}'.format(window_name))

hey there, I’m having difficulty figuring out how to get my template to match the game recording for my code. This is the test code that I’m trying to run, and it just doesn’t seem to work. I do realize I haven’t run the exact code that you put on your videos, but that is because I can’t seem to get it to window/video capture for the game I’m playing, (which is a little frustrating).
Nevertheless, it works for still image and it works fine videocapturing when I don’t try to matchTemplate but the two don’t seem to want to merge.

import numpy as np
from PIL import ImageGrab
import cv2
import time
import threading

def screen_record(): 
     last_time = time.time()
     while(True):
         # 800x600 windowed mode for GTA 5, at the top left position of your main screen.
         # 40 px accounts for title bar. 
         printscreen = np.array(ImageGrab.grab(bbox=(0,40,800,640)))
         print('loop took {} seconds'.format(time.time()-last_time))
         last_time = time.time()
         img_gray = cv2.imshow('window',cv2.cvtColor(printscreen, cv2.COLOR_BGR2GRAY))
         if cv2.waitKey(25) & 0xFF == ord('q'):
             cv2.destroyAllWindows()
             break

    eyes_hungry = cv2.imshow('hungry2.jpg',0)
    last_time = time.time()
    res = cv2.matchTemplate(img_gray, eyes_hungry, cv2.TM_CCOEFF_NORMED)       
    threshhold = 0.8
    loc = np.where(res >= threshhold)
    for pt in zip(*loc[::-1]):
        w, h = template.shape[::-1]
        cv2.rectangle(img_gray, pt, (pt[0]+w, pt[1]+h), (0,255,255), 1)


screen_record()

this is the error or a variation on the same error I get when I try running it:

  F:DesktopNeneat-python>grabscreen.py                                                    
loop took 0.0657804012298584 seconds                                                       
Traceback (most recent call last):                                                         
  File "F:DesktopNeneat-pythongrabscreen.py", line 29, in <module>                     
    screen_record()                                                                        
  File "F:DesktopNeneat-pythongrabscreen.py", line 22, in screen_record                
    res = cv2.matchTemplate(img_gray, eyes_hungry, cv2.TM_CCOEFF_NORMED)                   
cv2.error: OpenCV(4.5.3) C:UsersrunneradminAppDataLocalTemppip-req-build-sn_xpupmopencvmodulesimgprocsrctemplmatch.cpp:588: error: (-215:Assertion failed) corr.rows <= img.rows + templ.rows - 1 && corr.cols <= img.cols + templ.cols - 1 in function 'cv::crossCorr'

if you or anyone might be able to help, I’d really appreciate it, I’ve been banging my head on the wall for a few days now.

Thank you for reading.