navigation.py 文件源码

def find_contours(mask, smooth_factor=0.005):
        """ Find the contours in a given mask """
        border = 5
        # Canny detection breaks down with the edge of the image
        my_mask = cv2.copyMakeBorder(mask, border, border, border, border,
                                     cv2.BORDER_CONSTANT, value=(0, 0, 0))

        my_mask = cv2.cvtColor(my_mask, cv2.COLOR_BGR2GRAY)

        if is_cv2():
            contours, _ = cv2.findContours(my_mask, cv2.RETR_EXTERNAL,
                                           cv2.CHAIN_APPROX_SIMPLE)
        else:
            _, contours, _ = cv2.findContours(my_mask, cv2.RETR_EXTERNAL,
                                              cv2.CHAIN_APPROX_SIMPLE)

        # shift the contours back down
        for contour in contours:
            for pnt in contour:
                if pnt[0][1] > border:
                    pnt[0][1] = pnt[0][1] - border
                else:
                    pnt[0][1] = 0
                if pnt[0][0] > border:
                    pnt[0][0] = pnt[0][0] - border
                else:
                    pnt[0][0] = 0

        closed_contours = []
        for contour in contours:
            epsilon = smooth_factor*cv2.arcLength(contour, True)
            approx = cv2.approxPolyDP(contour, epsilon, True)
            area = cv2.contourArea(approx)
            # if they are too small they are not edges
            if area < 200:
                continue
            closed_contours.append(approx)

        return closed_contours