如何使for循環中的語句超時

Question

我正在編寫一個 python 腳本來使用 OpenCV 執行相機校准。

我發現cv2.findChessboardCorners函數可能需要很長時間才能在某些圖像上運行。

因此，我希望能夠在經過一段時間后停止該功能，然后繼續下一個圖像。

我怎么做？

for fname in images:        
    img = cv2.imread(fname)                            
    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    ret, corners = cv2.findChessboardCorners(gray, (20, 17), None)   

Answer 1

您可以使用 Pebble 作為多處理庫，它允許調度任務。 下面的代碼也使用了多線程進行處理：

from pebble import ProcessPool
from concurrent.futures import TimeoutError
import cv2
import glob
import os

CALIB_FOLDER = "path/to/folder"
# chessboard size
W = 10
H = 7


def f(fname):
    img = cv2.imread(fname)
    img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)
    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

    # Find the chessboard corners
    ret, corners = cv2.findChessboardCorners(gray, (W-1, H-1), None)
    return ret, corners


calib_imgs = glob.glob(os.path.join(CALIB_FOLDER, "*.jpg"))
calib_imgs = sorted(calib_imgs)

futures = []
with ProcessPool(max_workers=6) as pool:
    for fname in calib_imgs:          
        future = pool.schedule(f, args=[fname], timeout=10)
        futures.append(future)

for idx, future in enumerate(futures):
    try:
        ret, corners = future.result()  # blocks until results are ready
        print(ret)
    except TimeoutError as error:
        print("{} skipped. Took longer than {} seconds".format(calib_imgs[idx], error.args[1]))
    except Exception as error:
        print("Function raised %s" % error)
        print(error.traceback)  # traceback of the function