import numpy as np
import cv2

def test(cap):
    if not cap.isOpened():
        exit(1)

    while(True):
        ret, frame = cap.read()
        if not ret:
            break

        gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
        cv2.imshow('frame', gray)
        if cv2.waitKey(1) & 0xFF == ord('q'):
            break

    cap.release()
    cv2.destroyAllWindows()

class StaticImageSource(object):
    def __init__(self, image=None):
        self.image = image

    def isOpened(self):
        return self.image is not None

    def read(self, image=None):
        if self.image is None:
            return False, None
        if not image:
            return True, self.image.copy()
        np.copyto(image, self.image)
        return True, image

    def release(self):
        self.image = None

#cap = cv2.VideoCapture(0)
cap = StaticImageSource(cv2.imread('chocolate.png'))
test(cap)