showflow.py

#!/usr/bin/env python3

'''
showflow.py - Optical-flow demonstrations

    To test:

      % python showflow.py               # video from webcam
      % python showflow.py -f FILENAME   # video from file
      % python showflow.py -c CAMERA     # specific camera number
      % python showflow.py -s N          # scale-down factor for flow image
      % python showflow.py -m M          # move step in pixels

    Adapted from

    https://code.ros.org/trac/opencv/browser/trunk/opencv/samples/python/fback.py?rev=2271

    Copyright (C) 2014 Simon D. Levy

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as
    published by the Free Software Foundation, either version 3 of the
    License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
'''

import cv2

import time
import argparse

from optical_flow import OpticalFlowCalculator

if __name__ == '__main__':

    parser = argparse.ArgumentParser()

    parser.add_argument('-f', '--file',  dest='filename',
                        help='Read from video file', metavar='FILE')
    parser.add_argument('-s', '--scaledown', dest='scaledown',
                        help='Fractional image scaling', metavar='SCALEDOWN')
    parser.add_argument('-c', '--camera', dest='camera',
                        help='Camera number', metavar='CAMERA')
    parser.add_argument('-m', '--movestep', dest='movestep',
                        help='Move step (pixels)', metavar='MOVESTEP')

    args = parser.parse_args()

    camno = int(args.camera) if args.camera else 0

    cap = cv2.VideoCapture(camno if not args.filename else args.filename)

    width = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH))
    height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))

    scaledown = int(args.scaledown) if args.scaledown else 1

    movestep = int(args.movestep) if args.movestep else 16

    flow = OpticalFlowCalculator(width, height,
                                 window_name='Optical Flow',
                                 scaledown=scaledown,
                                 move_step=movestep)

    start_sec = time.time()
    count = 0
    while True:

        success, frame = cap.read()

        count += 1

        if not success:
            break

        result = flow.processFrame(frame)

        if not result:
            break

    elapsed_sec = time.time() - start_sec

    print('%dx%d image: %d frames in %3.3f sec = %3.3f frames / sec' %
          (width/scaledown, height/scaledown, count, elapsed_sec,
           count/elapsed_sec))