vision_util.py 文件源码

def canny(img, lowThreshold):
    """
    Performs canny edge detection on the provided grayscale image.
    :param img: a grayscale image
    :param lowThreshold: threshold for the canny operation
    :return: binary image containing the edges found by canny
    """

    dst = np.zeros(img.shape, dtype=img.dtype)
    cv2.blur(img, (3, 3), dst)

    # canny recommends that the high threshold be 3 times the low threshold
    # the kernel size is 3 as defined above
    return cv2.Canny(dst, lowThreshold, lowThreshold * 3, dst, 3)