opticalFlow.py

import numpy as np
import cv2, sys

# SPARSE OPTICAL FLOW
def sparseOpticalFlow():
    # use 0 for webcam capturing
    # cap = cv2.VideoCapture(0)

    cap = cv2.VideoCapture('test/Pedestrian overpass.mp4')

    # params for ShiTomasi corner detection
    feature_params = dict( maxCorners = 100,
                           qualityLevel = 0.3,
                           minDistance = 7,
                           blockSize = 7 )
    # Parameters for lucas kanade optical flow
    lk_params = dict( winSize  = (15,15),
                      maxLevel = 2,
                      criteria = (cv2.TERM_CRITERIA_EPS | cv2.TERM_CRITERIA_COUNT, 10, 0.03))
    # Create some random colors
    color = np.random.randint(0,255,(100,3))
    # Take first frame and find corners in it
    ret, old_frame = cap.read()
    old_gray = cv2.cvtColor(old_frame, cv2.COLOR_BGR2GRAY)
    p0 = cv2.goodFeaturesToTrack(old_gray, mask = None, **feature_params)
    # Create a mask image for drawing purposes
    mask = np.zeros_like(old_frame)
    while(1):
        ret,frame = cap.read()
        frame_gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
        # calculate optical flow
        p1, st, err = cv2.calcOpticalFlowPyrLK(old_gray, frame_gray, p0, None, **lk_params)
        # Select good points
        good_new = p1[st==1]
        good_old = p0[st==1]
        # draw the tracks
        for i,(new,old) in enumerate(zip(good_new,good_old)):
            a,b = new.ravel()
            c,d = old.ravel()
            mask = cv2.line(mask, (a,b),(c,d), color[i].tolist(), 2)
            frame = cv2.circle(frame,(a,b),5,color[i].tolist(),-1)
        img = cv2.add(frame,mask)
        cv2.imshow('frame',img)
        k = cv2.waitKey(30) & 0xff
        if k == 27:
            break
        # Now update the previous frame and previous points
        old_gray = frame_gray.copy()
        p0 = good_new.reshape(-1,1,2)
    cv2.destroyAllWindows()
    cap.release()


# DENSE OPTICAL FLOW
def denseOpticalFlow():
    # use 0 for webcam capturing
    # cap = cv2.VideoCapture(0)

    cap = cv2.VideoCapture('test/Pedestrian overpass.mp4')
    ret, frame1 = cap.read()
    prvs = cv2.cvtColor(frame1,cv2.COLOR_BGR2GRAY)
    hsv = np.zeros_like(frame1)
    hsv[...,1] = 255

    while(1):
        ret, frame2 = cap.read()
        next = cv2.cvtColor(frame2,cv2.COLOR_BGR2GRAY)
        flow = cv2.calcOpticalFlowFarneback(prvs,next, None, 0.5, 3, 15, 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)

        # print(np.sum(mag[100:300, 100:300]))
        if (np.sum(mag)> 100000):
            print('motion detected')

        bgr = cv2.cvtColor(hsv,cv2.COLOR_HSV2BGR)
        cv2.imshow('frame2',bgr)

        k = cv2.waitKey(30) & 0xff
        if k == 27:
            break
        elif k == ord('s'):
            cv2.imwrite('opticalfb.png',frame2)
            cv2.imwrite('opticalhsv.png',bgr)
        prvs = next

    cap.release()
    cv2.destroyAllWindows()

if __name__=='__main__':
    if sys.argv[1] == 'dense':
        denseOpticalFlow()
    elif sys.argv[1] == 'sparse':
        sparseOpticalFlow()
    else:
        print('Enter sparse for sparse optical flow, else dense')