filter_mask.py

def filter_mask(img):

    kernel = cv2.getStructuringElement(cv2.MORPH_ELLIPSE, (2, 2))

    # Fill any small holes
    closing = cv2.morphologyEx(img, cv2.MORPH_CLOSE, kernel)
    # Remove noise
    opening = cv2.morphologyEx(closing, cv2.MORPH_OPEN, kernel)

    # Dilate to merge adjacent blobs
    dilation = cv2.dilate(opening, kernel, iterations=2)

    # threshold
    th = dilation[dilation < 240] = 0

    return th