# Copyright 2023 The Flax Authors.
#
# 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
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# Copyright 2023 The Flax Authors.
#
# 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
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
This code is created with reference to torchvision/utils.py.

Modify: torch.tensor -> jax.numpy.DeviceArray
If you want to know about this file in detail, please visit the original code:
    https://github.com/pytorch/vision/blob/master/torchvision/utils.py
"""
import math

import jax.numpy as jnp
import numpy as np
from PIL import Image


def save_image(ndarray, fp, nrow=8, padding=2, pad_value=0.0, format_img=None):
  """Make a grid of images and Save it into an image file.

  Args:
    ndarray (array_like): 4D mini-batch images of shape (B x H x W x C)
    fp:  A filename(string) or file object
    nrow (int, optional): Number of images displayed in each row of the grid.
      The final grid size is ``(B / nrow, nrow)``. Default: ``8``.
    padding (int, optional): amount of padding. Default: ``2``.
    pad_value (float, optional): Value for the padded pixels. Default: ``0``.
    format_img(Optional):  If omitted, the format to use is determined from the
      filename extension. If a file object was used instead of a filename,
      this parameter should always be used.
  """

  if not (isinstance(ndarray, jnp.ndarray) or
          (isinstance(ndarray, list) and all(isinstance(t, jnp.ndarray) for t
                                             in ndarray))):
    raise TypeError(f'array_like of tensors expected, got {type(ndarray)}')

  ndarray = jnp.asarray(ndarray)

  if ndarray.ndim == 4 and ndarray.shape[-1] == 1:  # single-channel images
    ndarray = jnp.concatenate((ndarray, ndarray, ndarray), -1)

  # make the mini-batch of images into a grid
  nmaps = ndarray.shape[0]
  xmaps = min(nrow, nmaps)
  ymaps = int(math.ceil(float(nmaps) / xmaps))
  height, width = (int(ndarray.shape[1] + padding),
                   int(ndarray.shape[2] + padding))
  num_channels = ndarray.shape[3]
  grid = jnp.full((height * ymaps + padding, width * xmaps + padding,
                   num_channels), pad_value).astype(jnp.float32)
  k = 0
  for y in range(ymaps):
    for x in range(xmaps):
      if k >= nmaps:
        break
      grid = grid.at[y * height + padding:(y + 1) * height,
                     x * width + padding:(x + 1) * width].set(ndarray[k])
      k = k + 1

  # Add 0.5 after unnormalizing to [0, 255] to round to nearest integer
  ndarr = np.array(jnp.clip(grid * 255.0 + 0.5, 0, 255).astype(jnp.uint8))
  im = Image.fromarray(ndarr.copy())
  im.save(fp, format=format_img)
