crop-image-borders.py

def crop_image_borders(image_path):
    image = Image.open(image_path)
    image.load()
    ndarray_image = np.asarray(image)
    ndarray_image_mask = ndarray_image.max(axis=2)
    non_empty_columns = np.where(ndarray_image_mask.max(axis=0) > 0)[0]
    non_empty_rows = np.where(ndarray_image_mask.max(axis=1) > 0)[0]
    image_bbox = (min(non_empty_rows), max(non_empty_rows),
                  min(non_empty_columns), max(non_empty_columns))
    cropped_ndarray_image = ndarray_image[image_bbox[0]:image_bbox[1] + 1,
                                          image_bbox[2]:image_bbox[3] + 1, :]
    cropped_image = Image.fromarray(cropped_ndarray_image)
    cropped_image.save(image_path)