Mask encoding example for Kaggle OpenImages Instance Segmentation Competition

oid_mask_encoding.py

import base64
import numpy as np
from pycocotools import _mask as coco_mask
import typing as t
import zlib
def encode_binary_mask(mask: np.ndarray) -> t.Text:
 """Converts a binary mask into OID challenge encoding ascii text."""

 # check input mask --
 if mask.dtype != np.bool:
   raise ValueError(
       "encode_binary_mask expects a binary mask, received dtype == %s" %
       mask.dtype)

 mask = np.squeeze(mask)
 if len(mask.shape) != 2:
   raise ValueError(
       "encode_binary_mask expects a 2d mask, received shape == %s" %
       mask.shape)

 # convert input mask to expected COCO API input --
 mask_to_encode = mask.reshape(mask.shape[0], mask.shape[1], 1)
 mask_to_encode = mask_to_encode.astype(np.uint8)
 mask_to_encode = np.asfortranarray(mask_to_encode)

 # RLE encode mask --
 encoded_mask = coco_mask.encode(mask_to_encode)[0]["counts"]

 # compress and base64 encoding --
 binary_str = zlib.compress(encoded_mask, zlib.Z_BEST_COMPRESSION)
 base64_str = base64.b64encode(binary_str)
 return base64_str