from pathlib import Path
import cv2
以下の関数を呼び出してくると画像が開けない
#from classfy02 import input_data

def main():
    parent_path = Path(__file__).parent
    path = str(
        (parent_path / 'cross.png').resolve()
    )


    img = cv2.imread(path)
    cv2.namedWindow('screen', cv2.WINDOW_NORMAL)
    cv2.setWindowProperty('screen', cv2.WND_PROP_FULLSCREEN,
    cv2.WINDOW_FULLSCREEN)
    cv2.imshow('screen', img)
    cv2.waitKey(1000)

if __name__ == '__main__':
    main()

OpenCV Error: Assertion failed (size.width>0 && size.height>0) in imshow, file /Users/travis/build/skvark/opencv-
python/opencv/modules/highgui/src/window.cpp, line 325
Traceback (most recent call last):
File "path.py", line 15, in <module>
cv2.imshow('screen', img)
cv2.error: /Users/travis/build/skvark/opencv-
python/opencv/modules/highgui/src/window.cpp:325: error: (-215) size.width>0 && size.height>0 in function imshow