play video frame by frame

frame_player.py

#!/usr/bin/python3

import sys, cv2

video_file = sys.argv[1]
video = cv2.VideoCapture(video_file)
assert video.isOpened()
frame_cnt = int(video.get(cv2.CAP_PROP_FRAME_COUNT))

def read_frame(pos):
	video.set(cv2.CAP_PROP_POS_FRAMES, pos)
	ret, img = video.read()
	assert ret
	cv2.putText(img, '{}/{}'.format(pos + 1, frame_cnt), (10, 40),
			cv2.FONT_HERSHEY_SIMPLEX, 1.0,(0, 255, 0), 1, cv2.LINE_AA)
	return img

iframe = 0
cur_img = []
playing = False

while True:
	if int(video.get(cv2.CAP_PROP_POS_FRAMES)) != iframe + 1:
		cur_img = read_frame(iframe)
	cv2.imshow('frame', cur_img)
	key = cv2.waitKey(40 if playing else 0) & 0xFF
	if key == 27:
		break
	elif key == 32:
		playing = not playing

	if playing:
		iframe += 1
		if iframe >= frame_cnt:
			iframe = frame_cnt - 1
			playing = False
	else:
		if key == 81:
			iframe = max(iframe - 1, 0)
		elif key == 83:
			iframe = min(iframe + 1, frame_cnt - 1)
		elif key == 82:
			iframe = 0