Source code for

# Copyright 2020 - 2021 MONAI Consortium
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# See the License for the specific language governing permissions and
# limitations under the License.

from typing import Optional, Sequence, Union

import numpy as np

from monai.transforms import Resize
from monai.utils import InterpolateMode, ensure_tuple_rep, optional_import

Image, _ = optional_import("PIL", name="Image")

[docs]def write_png( data: np.ndarray, file_name: str, output_spatial_shape: Optional[Sequence[int]] = None, mode: Union[InterpolateMode, str] = InterpolateMode.BICUBIC, scale: Optional[int] = None, ) -> None: """ Write numpy data into png files to disk. Spatially it supports HW for 2D.(H,W) or (H,W,3) or (H,W,4). If `scale` is None, expect the input data in `np.uint8` or `np.uint16` type. It's based on the Image module in PIL library: Args: data: input data to write to file. file_name: expected file name that saved on disk. output_spatial_shape: spatial shape of the output image. mode: {``"nearest"``, ``"linear"``, ``"bilinear"``, ``"bicubic"``, ``"trilinear"``, ``"area"``} The interpolation mode. Defaults to ``"bicubic"``. See also: scale: {``255``, ``65535``} postprocess data by clipping to [0, 1] and scaling to [0, 255] (uint8) or [0, 65535] (uint16). Default is None to disable scaling. Raises: ValueError: When ``scale`` is not one of [255, 65535]. """ if not isinstance(data, np.ndarray): raise AssertionError("input data must be numpy array.") if len(data.shape) == 3 and data.shape[2] == 1: # PIL Image can't save image with 1 channel data = data.squeeze(2) if output_spatial_shape is not None: output_spatial_shape_ = ensure_tuple_rep(output_spatial_shape, 2) mode = InterpolateMode(mode) align_corners = None if mode in (InterpolateMode.NEAREST, InterpolateMode.AREA) else False xform = Resize(spatial_size=output_spatial_shape_, mode=mode, align_corners=align_corners) _min, _max = np.min(data), np.max(data) if len(data.shape) == 3: data = np.moveaxis(data, -1, 0) # to channel first data = xform(data) data = np.moveaxis(data, 0, -1) else: # (H, W) data = np.expand_dims(data, 0) # make a channel data = xform(data)[0] # first channel if mode != InterpolateMode.NEAREST: data = np.clip(data, _min, _max) if scale is not None: data = np.clip(data, 0.0, 1.0) # png writer only can scale data in range [0, 1] if scale == np.iinfo(np.uint8).max: data = (scale * data).astype(np.uint8) elif scale == np.iinfo(np.uint16).max: data = (scale * data).astype(np.uint16) else: raise ValueError(f"Unsupported scale: {scale}, available options are [255, 65535]") img = Image.fromarray(data), "PNG") return