opencv Edge detection Canny Edge Thresholds prototyping using Trackbars


Example

""" 
CannyTrackbar function allows for a better understanding of 
the mechanisms behind Canny Edge detection algorithm and rapid
prototyping. The example includes basic use case.

2 of the trackbars allow for tuning of the Canny function and
the other 2 help with understanding how basic filtering affects it.
"""
import cv2

def empty_function(*args):
    pass

def CannyTrackbar(img):
    win_name = "CannyTrackbars"

    cv2.namedWindow(win_name)
    cv2.resizeWindow(win_name, 500,100)

    cv2.createTrackbar("canny_th1", win_name, 0, 255, empty_function)
    cv2.createTrackbar("canny_th2", win_name, 0, 255, empty_function)
    cv2.createTrackbar("blur_size", win_name, 0, 255, empty_function)
    cv2.createTrackbar("blur_amp", win_name, 0, 255, empty_function)

    while True:
        cth1_pos = cv2.getTrackbarPos("canny_th1", win_name)
        cth2_pos = cv2.getTrackbarPos("canny_th2", win_name)
        bsize_pos = cv2.getTrackbarPos("blur_size", win_name)
        bamp_pos = cv2.getTrackbarPos("blur_amp", win_name)

        img_blurred = cv2.GaussianBlur(img.copy(), (trackbar_pos3 * 2 + 1, trackbar_pos3 * 2 + 1), bamp_pos)
        canny = cv2.Canny(img_blurred, cth1_pos, cth2_pos)
        cv2.imshow(win_name, canny)

        key = cv2.waitKey(1) & 0xFF
        if key == ord("c"):
            break

    cv2.destroyAllWindows()
    return canny

img = cv2.imread("image.jpg")
canny = CannyTrackbar(img)
cv2.imwrite("result.jpg", canny)