#! /usr/bin/env python
# -*- coding: utf-8 -*-

import numpy as np
import cv2

width  = 320
height = 240
margin =  50

cap = cv2.VideoCapture(0)

# Let us resize the video to width x height
cap.set(3,width)
cap.set(4,height)

# We need global variables
previous_frame = None
hsv            = np.zeros((height, width, 3), dtype = np.uint8)
hsv[...,1]     = 255

# Processing starts
while(True):
    is_ok, frame   = cap.read()
    frame          = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    if previous_frame != None : 
        flow       = cv2.calcOpticalFlowFarneback(previous_frame, frame, 
                                                  0.5, 3, 10, 3, 5, 1.2, 0)
        mag, ang   = cv2.cartToPolar(flow[...,0], flow[...,1])
        hsv[...,0] = ang*180/np.pi/2
        hsv[...,2] = cv2.normalize(mag,None,0,255,cv2.NORM_MINMAX)
        cv2.imshow('display',cv2.cvtColor(hsv,cv2.COLOR_HSV2BGR))
        if cv2.waitKey(1) & 0xFF == 27: #27 is the ascii for escape
            break
    previous_frame = frame

# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()