lucas_canade_method.py

import numpy as np
import cv2 as cv

# Open the video file
video_path = "slow_traffic_small.mp4"  # Name of the video file
cap = cv.VideoCapture(video_path)

# Check if the video file was successfully opened
if not cap.isOpened():
    print("Could not open video file!")
    exit()

# Parameters for Shi-Tomasi 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=(cv.TERM_CRITERIA_EPS | cv.TERM_CRITERIA_COUNT, 10, 0.03))

# Create some random colors
color = np.random.randint(0, 255, (100, 3))

# Read the first frame and detect corners
ret, old_frame = cap.read()
if not ret:
    print("Could not read the first frame of the video!")
    cap.release()
    exit()

old_gray = cv.cvtColor(old_frame, cv.COLOR_BGR2GRAY)
p0 = cv.goodFeaturesToTrack(old_gray, mask=None, **feature_params)

# Create a mask image for drawing purposes
mask = np.zeros_like(old_frame)

while True:
    ret, frame = cap.read()
    if not ret:
        print("Video ended or an error occurred!")
        break

    # Convert the frame to grayscale
    frame_gray = cv.cvtColor(frame, cv.COLOR_BGR2GRAY)

    # Calculate optical flow
    p1, st, err = cv.calcOpticalFlowPyrLK(old_gray, frame_gray, p0, None, **lk_params)

    # Select good points
    if p1 is not None:
        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 = cv.line(mask, (int(a), int(b)), (int(c), int(d)), color[i].tolist(), 2)
        frame = cv.circle(frame, (int(a), int(b)), 5, color[i].tolist(), -1)

    # Combine the frame with the mask
    img = cv.add(frame, mask)

    cv.imshow('Optical Flow', img)
    key = cv.waitKey(30) & 0xFF
    if key == 27:  # Exit on pressing the ESC key
        break

    # Update the previous frame and points
    old_gray = frame_gray.copy()
    p0 = good_new.reshape(-1, 1, 2)

cap.release()
cv.destroyAllWindows()