Project 8

import cv2
import numpy as np

def opticalflow():
    video=cv2.VideoCapture('traffic.mp4')
    fourcc=cv2.VideoWriter_fourcc(*'XVID')
    out=cv2.VideoWriter('output.avi',fourcc,30.0,(640,360))

    #creating a dict for shi-tomasi corener detection by specifying the parameters
    stomasi_features=dict(
        maxCorners = 100,
        qualityLevel = 0.01,
        minDistance = 10,
        blockSize = 7 )


    #creater a dict to  pre  specify parameters for lucas kanade method
    lk_parameters=dict(
                winSize  = (15,15),
                maxLevel = 2,
                criteria = (cv2.TERM_CRITERIA_EPS | cv2.TERM_CRITERIA_COUNT, 10, 0.03)
    )


    #creating random colors
    colors=np.random.randint(0,255,(100,3))

    #now we take first frame and detec shi-tomasi corners in it by first reading the #frame and then converting it to gray scale and then using cv2.goodfeatures totrack() #method
    ret,frame1=video.read()
    frame1_gray=cv2.cvtColor(frame1,cv2.COLOR_BGR2GRAY)

    F1_points=cv2.goodFeaturesToTrack(frame1_gray,mask=None,**stomasi_features)

    #create maask img for drawing
    mask=np.zeros_like(frame1)

    #now here we read the next frame convert it to grayscale then calculate optical flow #in the new frame and the frame 1
    while True:
        ret,frame2=video.read()
        frame2_gray=cv2.cvtColor(frame2,cv2.COLOR_BGR2GRAY)

        F2_points,status,err=cv2.calcOpticalFlowPyrLK(frame1_gray,frame2_gray,F1_points,None,**lk_parameters)

    #selecting good points from the above optical flow method and comparing it with old #points
        good_new=F2_points[status==1]
        good_old=F1_points[status==1]

    #drawing lines
        for colour,(new,old) in enumerate(zip(good_new,good_old)):
            a,b=new.ravel()   #this the coordinate of the new point from the frame 2
            c,d=old.ravel()   #this is coordinateof old point from frame 1

            mask= cv2.line(mask,(int(a),int(b)),(int(c),int(d)),colors[colour].tolist(),2)
            frame2=cv2.circle(frame2,(int(a),int(b)),5,colors[colour].tolist(),-1)

        img=cv2.add(frame2,mask)
        #out.write(img)

        cv2.imshow('FRAME',img)
        cv2.imshow('mask',mask)
        out.write(img)

        k = cv2.waitKey(30)
        if k == 27  & 0xff:
            break
        
        #update previous points and frame
        frame1_gray=frame2_gray.copy()
        F1_points=good_new.reshape(-1,1,2)

    cv2.destroyAllWindows()
    out.release()
    video.release()


if __name__ == '__main__':
    opticalflow()