# Copyright 2016 The TensorFlow Authors. All Rights Reserved.
#
# 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.
# ==============================================================================
"""Provides utilities to preprocess images in CIFAR-10.
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import tensorflow as tf
_PADDING = 4
slim = tf.contrib.slim
def preprocess_for_train(image,
output_height,
output_width,
padding=_PADDING):
"""Preprocesses the given image for training.
Note that the actual resizing scale is sampled from
[`resize_size_min`, `resize_size_max`].
Args:
image: A `Tensor` representing an image of arbitrary size.
output_height: The height of the image after preprocessing.
output_width: The width of the image after preprocessing.
padding: The amound of padding before and after each dimension of the image.
Returns:
A preprocessed image.
"""
tf.summary.image('image', tf.expand_dims(image, 0))
# Transform the image to floats.
image = tf.to_float(image)
if padding > 0:
image = tf.pad(image, [[padding, padding], [padding, padding], [0, 0]])
# Randomly crop a [height, width] section of the image.
distorted_image = tf.random_crop(image,
[output_height, output_width, 3])
# Randomly flip the image horizontally.
distorted_image = tf.image.random_flip_left_right(distorted_image)
tf.summary.image('distorted_image', tf.expand_dims(distorted_image, 0))
# Because these operations are not commutative, consider randomizing
# the order their operation.
distorted_image = tf.image.random_brightness(distorted_image,
max_delta=63)
distorted_image = tf.image.random_contrast(distorted_image,
lower=0.2, upper=1.8)
# Subtract off the mean and divide by the variance of the pixels.
return tf.image.per_image_standardization(distorted_image)
def preprocess_for_eval(image, output_height, output_width):
"""Preprocesses the given image for evaluation.
Args:
image: A `Tensor` representing an image of arbitrary size.
output_height: The height of the image after preprocessing.
output_width: The width of the image after preprocessing.
Returns:
A preprocessed image.
"""
tf.summary.image('image', tf.expand_dims(image, 0))
# Transform the image to floats.
image = tf.to_float(image)
# Resize and crop if needed.
resized_image = tf.image.resize_image_with_crop_or_pad(image,
output_width,
output_height)
tf.summary.image('resized_image', tf.expand_dims(resized_image, 0))
# Subtract off the mean and divide by the variance of the pixels.
return tf.image.per_image_standardization(resized_image)
def preprocess_image(image, output_height, output_width, is_training=False):
"""Preprocesses the given image.
Args:
image: A `Tensor` representing an image of arbitrary size.
output_height: The height of the image after preprocessing.
output_width: The width of the image after preprocessing.
is_training: `True` if we're preprocessing the image for training and
`False` otherwise.
Returns:
A preprocessed image.
"""
if is_training:
return preprocess_for_train(image, output_height, output_width)
else:
return preprocess_for_eval(image, output_height, output_width)
