Source code for neodroidvision.segmentation.masks.run_length_encoding

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
import numpy

__author__ = "Christian Heider Nielsen"
__doc__ = r"""

           Created on 20/10/2019
           """

__all__ = ["run_length_to_mask", "mask_to_run_length"]


def run_length_to_mask(
    mask_rle: str = "", shape: tuple = (1400, 2100)
) -> numpy.ndarray:
    """
    Decode rle encoded mask.

    :param mask_rle: run-length as string formatted (start length)
    :param shape: (height, width) of array to return
    Returns numpy array, 1 - mask, 0 - background"""
    s = mask_rle.split()
    starts, lengths = [numpy.asarray(x, dtype=int) for x in (s[0:][::2], s[1:][::2])]
    starts -= 1
    ends = starts + lengths
    img = numpy.zeros(shape[0] * shape[1], dtype=numpy.uint8)
    for lo, hi in zip(starts, ends):
        img[lo:hi] = 1
    return img.reshape(shape, order="F")


def mask_to_run_length(img: numpy.ndarray) -> str:
    """
    Convert mask to rle.
    img: numpy array, 1 - mask, 0 - background
    Returns run length as string formated"""
    pixels = img.T.flatten()
    pixels = numpy.concatenate([[0], pixels, [0]])
    runs = numpy.where(pixels[1:] != pixels[:-1])[0] + 1
    runs[1::2] -= runs[::2]
    return " ".join(str(x) for x in runs)