window_image.py

import win32gui
import win32ui
from ctypes import windll
from PIL import Image

toplist, winlist = [], []
def enum_cb(hwnd, results):
    winlist.append((hwnd, win32gui.GetWindowText(hwnd)))
win32gui.EnumWindows(enum_cb, toplist)
volmixsingleton = [(hwnd, title) for hwnd, title in winlist if "volume mixer - " in title.lower()]
volmixtitle = volmixsingleton[0][1]
hwnd = win32gui.FindWindow(None, volmixtitle)

left, top, right, bot = win32gui.GetWindowRect(hwnd)
w = right - left
h = bot - top

hwndDC = win32gui.GetWindowDC(hwnd)
mfcDC  = win32ui.CreateDCFromHandle(hwndDC)
saveDC = mfcDC.CreateCompatibleDC()

saveBitMap = win32ui.CreateBitmap()
saveBitMap.CreateCompatibleBitmap(mfcDC, w, h)

saveDC.SelectObject(saveBitMap)

def snapshot():
    result = windll.user32.PrintWindow(hwnd, saveDC.GetSafeHdc(), 0)

    bmpinfo = saveBitMap.GetInfo()
    bmpstr = saveBitMap.GetBitmapBits(True)

    im = Image.frombuffer(
        'RGB',
        (bmpinfo['bmWidth'], bmpinfo['bmHeight']),
        bmpstr, 'raw', 'BGRX', 0, 1)
    return im