DeepLab 源码分析之 core/preprocess_utils.py
我们分析core文件夹下的 preprocess_utils.py 文件
这个文件主要包含数据预处理的各项函数
import tensorflow as tf函数 flip_dim
用于图像翻转 dim=1 水平翻转
def flip_dim(tensor_list, prob=0.5, dim=1):
"""Randomly flips a dimension of the given tensor.
The decision to randomly flip the `Tensors` is made together. In other words,
all or none of the images pass in are flipped.
Note that tf.random_flip_left_right and tf.random_flip_up_down isn't used so
that we can control for the probability as well as ensure the same decision
is applied across the images.
Args:
tensor_list: A list of `Tensors` with the same number of dimensions.
prob: The probability of a left-right flip.
dim: The dimension to flip, 0, 1, ..
Returns:
outputs: A list of the possibly flipped `Tensors` as well as an indicator
`Tensor` at the end whose value is `True` if the inputs were flipped and
`False` otherwise.
Raises:
ValueError: If dim is negative or greater than the dimension of a `Tensor`.
"""
random_value = tf.random_uniform([])
def flip():
flipped = []
for tensor in tensor_list:
if dim < 0 or dim >= len(tensor.get_shape().as_list()):
raise ValueError('dim must represent a valid dimension.')
flipped.append(tf.reverse_v2(tensor, [dim]))
return flipped
is_flipped = tf.less_equal(random_value, prob)
outputs = tf.cond(is_flipped, flip, lambda: tensor_list)
if not isinstance(outputs, (list, tuple)):
outputs = [outputs]
outputs.append(is_flipped)
return outputs函数 pad_to_bounding_box
根据给定的pad_value，填充image
def pad_to_bounding_box(image, offset_height, offset_width, target_height,
target_width, pad_value):
"""Pads the given image with the given pad_value.
Works like tf.image.pad_to_bounding_box, except it can pad the image
with any given arbitrary pad value and also handle images whose sizes are not
known during graph construction.
Args:
image: 3-D tensor with shape [height, width, channels]
offset_height: Number of rows of zeros to add on top.
offset_width: Number of columns of zeros to add on the left.
target_height: Height of output image.
target_width: Width of output image.
pad_value: Value to pad the image tensor with.
Returns:
3-D tensor of shape [target_height, target_width, channels].
Raises:
ValueError: If the shape of image is incompatible with the offset_* or
target_* arguments.
"""
image_rank = tf.rank(image)
image_rank_assert = tf.Assert(
tf.equal(image_rank, 3),
['Wrong image tensor rank [Expected] [Actual]',
3, image_rank])
with tf.control_dependencies([image_rank_assert]):
image -= pad_value
image_shape = tf.shape(image)
height, width = image_shape[0], image_shape[1]
target_width_assert = tf.Assert(
tf.greater_equal(
target_width, width),
['target_width must be >= width'])
target_height_assert = tf.Assert(
tf.greater_equal(target_height, height),
['target_height must be >= height'])
with tf.control_dependencies([target_width_assert]):
after_padding_width = target_width - offset_width - width
with tf.control_dependencies([target_height_assert]):
after_padding_height = target_height - offset_height - height
offset_assert = tf.Assert(
tf.logical_and(
tf.greater_equal(after_padding_width, 0),
tf.greater_equal(after_padding_height, 0)),
['target size not possible with the given target offsets'])
height_params = tf.stack([offset_height, after_padding_height])
width_params = tf.stack([offset_width, after_padding_width])
channel_params = tf.stack([0, 0])
with tf.control_dependencies([offset_assert]):
paddings = tf.stack([height_params, width_params, channel_params])
padded = tf.pad(image, paddings)
return padded + pad_value函数 _crop
def _crop(image, offset_height, offset_width, crop_height, crop_width):
"""Crops the given image using the provided offsets and sizes.
Note that the method doesn't assume we know the input image size but it does
assume we know the input image rank.
Args:
image: an image of shape [height, width, channels].
offset_height: a scalar tensor indicating the height offset.
offset_width: a scalar tensor indicating the width offset.
crop_height: the height of the cropped image.
crop_width: the width of the cropped image.
Returns:
The cropped (and resized) image.
Raises:
ValueError: if `image` doesn't have rank of 3.
InvalidArgumentError: if the rank is not 3 or if the image dimensions are
less than the crop size.
"""
original_shape = tf.shape(image)
if len(image.get_shape().as_list()) != 3:
raise ValueError('input must have rank of 3')
original_channels = image.get_shape().as_list()[2]
rank_assertion = tf.Assert(
tf.equal(tf.rank(image), 3),
['Rank of image must be equal to 3.'])
with tf.control_dependencies([rank_assertion]):
cropped_shape = tf.stack([crop_height, crop_width, original_shape[2]])
size_assertion = tf.Assert(
tf.logical_and(
tf.greater_equal(original_shape[0], crop_height),
tf.greater_equal(original_shape[1], crop_width)),
['Crop size greater than the image size.'])
offsets = tf.to_int32(tf.stack([offset_height, offset_width, 0]))
# Use tf.slice instead of crop_to_bounding box as it accepts tensors to
# define the crop size.
with tf.control_dependencies([size_assertion]):
image = tf.slice(image, offsets, cropped_shape)
image = tf.reshape(image, cropped_shape)
image.set_shape([crop_height, crop_width, original_channels])
return image函数 random_crop
def random_crop(image_list, crop_height, crop_width):
"""Crops the given list of images.
The function applies the same crop to each image in the list. This can be
effectively applied when there are multiple image inputs of the same
dimension such as:
image, depths, normals = random_crop([image, depths, normals], 120, 150)
Args:
image_list: a list of image tensors of the same dimension but possibly
varying channel.
crop_height: the new height.
crop_width: the new width.
Returns:
the image_list with cropped images.
Raises:
ValueError: if there are multiple image inputs provided with different size
or the images are smaller than the crop dimensions.
"""
if not image_list:
raise ValueError('Empty image_list.')
# Compute the rank assertions.
rank_assertions = []
for i in range(len(image_list)):
image_rank = tf.rank(image_list[i])
rank_assert = tf.Assert(
tf.equal(image_rank, 3),
['Wrong rank for tensor %s [expected] [actual]',
image_list[i].name, 3, image_rank])
rank_assertions.append(rank_assert)
with tf.control_dependencies([rank_assertions[0]]):
image_shape = tf.shape(image_list[0])
image_height = image_shape[0]
image_width = image_shape[1]
crop_size_assert = tf.Assert(
tf.logical_and(
tf.greater_equal(image_height, crop_height),
tf.greater_equal(image_width, crop_width)),
['Crop size greater than the image size.'])
asserts = [rank_assertions[0], crop_size_assert]
for i in range(1, len(image_list)):
image = image_list[i]
asserts.append(rank_assertions[i])
with tf.control_dependencies([rank_assertions[i]]):
shape = tf.shape(image)
height = shape[0]
width = shape[1]
height_assert = tf.Assert(
tf.equal(height, image_height),
['Wrong height for tensor %s [expected][actual]',
image.name, height, image_height])
width_assert = tf.Assert(
tf.equal(width, image_width),
['Wrong width for tensor %s [expected][actual]',
image.name, width, image_width])
asserts.extend([height_assert, width_assert])
# Create a random bounding box.
#
# Use tf.random_uniform and not numpy.random.rand as doing the former would
# generate random numbers at graph eval time, unlike the latter which
# generates random numbers at graph definition time.
with tf.control_dependencies(asserts):
max_offset_height = tf.reshape(image_height - crop_height + 1, [])
max_offset_width = tf.reshape(image_width - crop_width + 1, [])
offset_height = tf.random_uniform(
[], maxval=max_offset_height, dtype=tf.int32)
offset_width = tf.random_uniform(
[], maxval=max_offset_width, dtype=tf.int32)
return [_crop(image, offset_height, offset_width,
crop_height, crop_width) for image in image_list]
函数 get_random_scale
def get_random_scale(min_scale_factor, max_scale_factor, step_size):
"""Gets a random scale value.
Args:
min_scale_factor: Minimum scale value.
max_scale_factor: Maximum scale value.
step_size: The step size from minimum to maximum value.
Returns:
A random scale value selected between minimum and maximum value.
Raises:
ValueError: min_scale_factor has unexpected value.
"""
if min_scale_factor < 0 or min_scale_factor > max_scale_factor:
raise ValueError('Unexpected value of min_scale_factor.')
if min_scale_factor == max_scale_factor:
return tf.to_float(min_scale_factor)
# When step_size = 0, we sample the value uniformly from [min, max).
if step_size == 0:
return tf.random_uniform([1],
minval=min_scale_factor,
maxval=max_scale_factor)
# When step_size != 0, we randomly select one discrete value from [min, max].
num_steps = int((max_scale_factor - min_scale_factor) / step_size + 1)
scale_factors = tf.lin_space(min_scale_factor, max_scale_factor, num_steps)
shuffled_scale_factors = tf.random_shuffle(scale_factors)
return shuffled_scale_factors[0]函数 randomly_scale_image_and_label 随机放缩
def randomly_scale_image_and_label(image, label=None, scale=1.0):
"""Randomly scales image and label.
Args:
image: Image with shape [height, width, 3].
label: Label with shape [height, width, 1].
scale: The value to scale image and label.
Returns:
Scaled image and label.
"""
# No random scaling if scale == 1.
if scale == 1.0:
return image, label
image_shape = tf.shape(image)
new_dim = tf.to_int32(tf.to_float([image_shape[0], image_shape[1]]) * scale)
# Need squeeze and expand_dims because image interpolation takes
# 4D tensors as input.
image = tf.squeeze(tf.image.resize_bilinear(
tf.expand_dims(image, 0),
new_dim,
align_corners=True), [0])
if label is not None:
label = tf.squeeze(tf.image.resize_nearest_neighbor(
tf.expand_dims(label, 0),
new_dim,
align_corners=True), [0])
return image, label函数 resolve_shape 形状
def resolve_shape(tensor, rank=None, scope=None):
"""Fully resolves the shape of a Tensor.
Use as much as possible the shape components already known during graph
creation and resolve the remaining ones during runtime.
Args:
tensor: Input tensor whose shape we query.
rank: The rank of the tensor, provided that we know it.
scope: Optional name scope.
Returns:
shape: The full shape of the tensor.
"""
with tf.name_scope(scope, 'resolve_shape', [tensor]):
if rank is not None:
shape = tensor.get_shape().with_rank(rank).as_list()
else:
shape = tensor.get_shape().as_list()
if None in shape:
shape_dynamic = tf.shape(tensor)
for i in range(len(shape)):
if shape[i] is None:
shape[i] = shape_dynamic[i]
return shape函数 resize_to_range
def resize_to_range(image,
label=None,
min_size=None,
max_size=None,
factor=None,
align_corners=True,
label_layout_is_chw=False,
scope=None,
method=tf.image.ResizeMethod.BILINEAR):
"""Resizes image or label so their sides are within the provided range.
The output size can be described by two cases:
1. If the image can be rescaled so its minimum size is equal to min_size
without the other side exceeding max_size, then do so.
2. Otherwise, resize so the largest side is equal to max_size.
An integer in `range(factor)` is added to the computed sides so that the
final dimensions are multiples of `factor` plus one.
Args:
image: A 3D tensor of shape [height, width, channels].
label: (optional) A 3D tensor of shape [height, width, channels] (default)
or [channels, height, width] when label_layout_is_chw = True.
min_size: (scalar) desired size of the smaller image side.
max_size: (scalar) maximum allowed size of the larger image side. Note
that the output dimension is no larger than max_size and may be slightly
smaller than min_size when factor is not None.
factor: Make output size multiple of factor plus one.
align_corners: If True, exactly align all 4 corners of input and output.
label_layout_is_chw: If true, the label has shape [channel, height, width].
We support this case because for some instance segmentation dataset, the
instance segmentation is saved as [num_instances, height, width].
scope: Optional name scope.
method: Image resize method. Defaults to tf.image.ResizeMethod.BILINEAR.
Returns:
A 3-D tensor of shape [new_height, new_width, channels], where the image
has been resized (with the specified method) so that
min(new_height, new_width) == ceil(min_size) or
max(new_height, new_width) == ceil(max_size).
Raises:
ValueError: If the image is not a 3D tensor.
"""
with tf.name_scope(scope, 'resize_to_range', [image]):
new_tensor_list = []
min_size = tf.to_float(min_size)
if max_size is not None:
max_size = tf.to_float(max_size)
# Modify the max_size to be a multiple of factor plus 1 and make sure the
# max dimension after resizing is no larger than max_size.
if factor is not None:
max_size = (max_size + (factor - (max_size - 1) % factor) % factor
- factor)
[orig_height, orig_width, _] = resolve_shape(image, rank=3)
orig_height = tf.to_float(orig_height)
orig_width = tf.to_float(orig_width)
orig_min_size = tf.minimum(orig_height, orig_width)
# Calculate the larger of the possible sizes
large_scale_factor = min_size / orig_min_size
large_height = tf.to_int32(tf.ceil(orig_height * large_scale_factor))
large_width = tf.to_int32(tf.ceil(orig_width * large_scale_factor))
large_size = tf.stack([large_height, large_width])
new_size = large_size
if max_size is not None:
# Calculate the smaller of the possible sizes, use that if the larger
# is too big.
orig_max_size = tf.maximum(orig_height, orig_width)
small_scale_factor = max_size / orig_max_size
small_height = tf.to_int32(tf.ceil(orig_height * small_scale_factor))
small_width = tf.to_int32(tf.ceil(orig_width * small_scale_factor))
small_size = tf.stack([small_height, small_width])
new_size = tf.cond(
tf.to_float(tf.reduce_max(large_size)) > max_size,
lambda: small_size,
lambda: large_size)
# Ensure that both output sides are multiples of factor plus one.
if factor is not None:
new_size += (factor - (new_size - 1) % factor) % factor
new_tensor_list.append(tf.image.resize_images(
image, new_size, method=method, align_corners=align_corners))
if label is not None:
if label_layout_is_chw:
# Input label has shape [channel, height, width].
resized_label = tf.expand_dims(label, 3)
resized_label = tf.image.resize_nearest_neighbor(
resized_label, new_size, align_corners=align_corners)
resized_label = tf.squeeze(resized_label, 3)
else:
# Input label has shape [height, width, channel].
resized_label = tf.image.resize_images(
label, new_size, method=tf.image.ResizeMethod.NEAREST_NEIGHBOR,
align_corners=align_corners)
new_tensor_list.append(resized_label)
else:
new_tensor_list.append(None)
return new_tensor_list