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221 lines
8.2 KiB
221 lines
8.2 KiB
# Copyright 2018 The TensorFlow Authors. All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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# ==============================================================================
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"""ImageNet preprocessing for MnasNet."""
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from __future__ import absolute_import
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from __future__ import division
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from __future__ import print_function
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import tensorflow as tf
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import numpy as np
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IMAGE_SIZE = 224
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CROP_PADDING = 32
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def distorted_bounding_box_crop(image_bytes,
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bbox,
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min_object_covered=0.1,
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aspect_ratio_range=(0.75, 1.33),
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area_range=(0.05, 1.0),
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max_attempts=100,
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scope=None):
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"""Generates cropped_image using one of the bboxes randomly distorted.
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See `tf.image.sample_distorted_bounding_box` for more documentation.
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Args:
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image_bytes: `Tensor` of binary image data.
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bbox: `Tensor` of bounding boxes arranged `[1, num_boxes, coords]`
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where each coordinate is [0, 1) and the coordinates are arranged
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as `[ymin, xmin, ymax, xmax]`. If num_boxes is 0 then use the whole
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image.
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min_object_covered: An optional `float`. Defaults to `0.1`. The cropped
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area of the image must contain at least this fraction of any bounding
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box supplied.
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aspect_ratio_range: An optional list of `float`s. The cropped area of the
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image must have an aspect ratio = width / height within this range.
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area_range: An optional list of `float`s. The cropped area of the image
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must contain a fraction of the supplied image within in this range.
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max_attempts: An optional `int`. Number of attempts at generating a cropped
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region of the image of the specified constraints. After `max_attempts`
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failures, return the entire image.
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scope: Optional `str` for name scope.
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Returns:
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cropped image `Tensor`
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"""
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with tf.name_scope(scope, 'distorted_bounding_box_crop', [image_bytes, bbox]):
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shape = tf.image.extract_jpeg_shape(image_bytes)
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sample_distorted_bounding_box = tf.image.sample_distorted_bounding_box(
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shape,
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bounding_boxes=bbox,
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min_object_covered=min_object_covered,
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aspect_ratio_range=aspect_ratio_range,
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area_range=area_range,
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max_attempts=max_attempts,
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use_image_if_no_bounding_boxes=True)
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bbox_begin, bbox_size, _ = sample_distorted_bounding_box
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# Crop the image to the specified bounding box.
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offset_y, offset_x, _ = tf.unstack(bbox_begin)
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target_height, target_width, _ = tf.unstack(bbox_size)
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crop_window = tf.stack([offset_y, offset_x, target_height, target_width])
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image = tf.image.decode_and_crop_jpeg(image_bytes, crop_window, channels=3)
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return image
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def _at_least_x_are_equal(a, b, x):
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"""At least `x` of `a` and `b` `Tensors` are equal."""
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match = tf.equal(a, b)
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match = tf.cast(match, tf.int32)
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return tf.greater_equal(tf.reduce_sum(match), x)
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def _decode_and_random_crop(image_bytes, image_size):
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"""Make a random crop of image_size."""
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bbox = tf.constant([0.0, 0.0, 1.0, 1.0], dtype=tf.float32, shape=[1, 1, 4])
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image = distorted_bounding_box_crop(
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image_bytes,
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bbox,
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min_object_covered=0.1,
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aspect_ratio_range=(3. / 4, 4. / 3.),
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area_range=(0.08, 1.0),
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max_attempts=10,
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scope=None)
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original_shape = tf.image.extract_jpeg_shape(image_bytes)
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bad = _at_least_x_are_equal(original_shape, tf.shape(image), 3)
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image = tf.cond(
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bad,
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lambda: _decode_and_center_crop(image_bytes, image_size),
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lambda: tf.image.resize_bicubic([image], # pylint: disable=g-long-lambda
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[image_size, image_size])[0])
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return image
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def _decode_and_center_crop(image_bytes, image_size):
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"""Crops to center of image with padding then scales image_size."""
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shape = tf.image.extract_jpeg_shape(image_bytes)
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image_height = shape[0]
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image_width = shape[1]
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padded_center_crop_size = tf.cast(
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((image_size / (image_size + CROP_PADDING)) *
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tf.cast(tf.minimum(image_height, image_width), tf.float32)),
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tf.int32)
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offset_height = ((image_height - padded_center_crop_size) + 1) // 2
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offset_width = ((image_width - padded_center_crop_size) + 1) // 2
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crop_window = tf.stack([offset_height, offset_width,
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padded_center_crop_size, padded_center_crop_size])
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image = tf.image.decode_and_crop_jpeg(image_bytes, crop_window, channels=3)
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image = tf.image.resize_bicubic([image], [image_size, image_size])[0]
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return image
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def _flip(image):
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"""Random horizontal image flip."""
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image = tf.image.random_flip_left_right(image)
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return image
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def preprocess_for_train(image_bytes, use_bfloat16, image_size=IMAGE_SIZE):
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"""Preprocesses the given image for evaluation.
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Args:
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image_bytes: `Tensor` representing an image binary of arbitrary size.
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use_bfloat16: `bool` for whether to use bfloat16.
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image_size: image size.
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Returns:
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A preprocessed image `Tensor`.
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"""
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image = _decode_and_random_crop(image_bytes, image_size)
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image = _flip(image)
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image = tf.reshape(image, [image_size, image_size, 3])
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image = tf.image.convert_image_dtype(
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image, dtype=tf.bfloat16 if use_bfloat16 else tf.float32)
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return image
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def preprocess_for_eval(image_bytes, use_bfloat16, image_size=IMAGE_SIZE):
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"""Preprocesses the given image for evaluation.
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Args:
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image_bytes: `Tensor` representing an image binary of arbitrary size.
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use_bfloat16: `bool` for whether to use bfloat16.
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image_size: image size.
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Returns:
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A preprocessed image `Tensor`.
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"""
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image = _decode_and_center_crop(image_bytes, image_size)
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image = tf.reshape(image, [image_size, image_size, 3])
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image = tf.image.convert_image_dtype(
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image, dtype=tf.bfloat16 if use_bfloat16 else tf.float32)
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return image
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def preprocess_image(image_bytes,
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is_training=False,
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use_bfloat16=False,
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image_size=IMAGE_SIZE):
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"""Preprocesses the given image.
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Args:
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image_bytes: `Tensor` representing an image binary of arbitrary size.
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is_training: `bool` for whether the preprocessing is for training.
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use_bfloat16: `bool` for whether to use bfloat16.
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image_size: image size.
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Returns:
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A preprocessed image `Tensor` with value range of [0, 255].
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"""
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if is_training:
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return preprocess_for_train(image_bytes, use_bfloat16, image_size)
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else:
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return preprocess_for_eval(image_bytes, use_bfloat16, image_size)
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class TfPreprocessTransform:
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def __init__(self, is_training=False, size=224):
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self.is_training = is_training
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self.size = size[0] if isinstance(size, tuple) else size
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self._image_bytes = None
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self.process_image = self._build_tf_graph()
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self.sess = None
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def _build_tf_graph(self):
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with tf.device('/cpu:0'):
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self._image_bytes = tf.placeholder(
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shape=[],
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dtype=tf.string,
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)
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img = preprocess_image(self._image_bytes, self.is_training, False, self.size)
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return img
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def __call__(self, image_bytes):
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if self.sess is None:
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self.sess = tf.Session()
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img = self.sess.run(self.process_image, feed_dict={self._image_bytes: image_bytes})
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img = img.round().clip(0, 255).astype(np.uint8)
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if img.ndim < 3:
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img = np.expand_dims(img, axis=-1)
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img = np.rollaxis(img, 2) # HWC to CHW
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return img
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