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    Create a Line Drawing from Webcam Stream using OpenCV in Python

    What will we cover in this tutorial?

    How to convert a webcam stream into a black and white line drawing using OpenCV and Python. Also, how to adjust the parameters while running the live stream.

    See result here.

    The things you need to use

    There are two things you need to use in order to get a good line drawing of your image.

    1. GaussianBlur to smooth out the image, as detecting lines is sensitive to noise.
    2. Canny that detects the lines.

    The Gaussian blur is advised to use a 5×5 filter. The Canny then has to threshold parameters. To find the optimal values for your setting, we have inserted two trackbars where you can set them to any value as see the results.

    You can read more about Canny Edge Detection here.

    If you need to install OpenCV please read this tutorial.

    The code is given below.

    import cv2
    import numpy as np
    # Setup camera
    cap = cv2.VideoCapture(0)
    # Set a smaller resolution
    cap.set(cv2.CAP_PROP_FRAME_WIDTH, 640)
    cap.set(cv2.CAP_PROP_FRAME_HEIGHT, 480)
    def nothing(x):
    canny = "Canny"
    cv2.createTrackbar('Threshold 1', canny, 0, 255, nothing)
    cv2.createTrackbar('Threshold 2', canny, 0, 255, nothing)
    while True:
        # Capture frame-by-frame
        _, frame = cap.read()
        frame = cv2.flip(frame, 1)
        t1 = cv2.getTrackbarPos('Threshold 1', canny)
        t2 = cv2.getTrackbarPos('Threshold 2', canny)
        gb = cv2.GaussianBlur(frame, (5, 5), 0)
        can = cv2.Canny(gb, t1, t2)
        cv2.imshow(canny, can)
        frame[np.where(can)] = 255
        cv2.imshow('WebCam', frame)
        if cv2.waitKey(1) == ord('q'):
    # When everything done, release the capture

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