"""Utilities for ImageNet data preprocessing & prediction decoding.
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import json
import warnings
import numpy as np
import tensorflow.keras as keras
CLASS_INDEX = None
CLASS_INDEX_PATH = ('https://storage.googleapis.com/download.tensorflow.org/'
'data/imagenet_class_index.json')
backend = keras.backend
layers = keras.layers
models = keras.models
keras_utils = keras.utils
def _preprocess_numpy_input(x, data_format, mode, **kwargs):
"""Preprocesses a Numpy array encoding a batch of images.
# Arguments
x: Input array, 3D or 4D.
data_format: Data format of the image array.
mode: One of "caffe", "tf" or "torch".
- caffe: will convert the images from RGB to BGR,
then will zero-center each color channel with
respect to the ImageNet dataset,
without scaling.
- tf: will scale pixels between -1 and 1,
sample-wise.
- torch: will scale pixels between 0 and 1 and then
will normalize each channel with respect to the
ImageNet dataset.
# Returns
Preprocessed Numpy array.
"""
if not issubclass(x.dtype.type, np.floating):
x = x.astype(backend.floatx(), copy=False)
if mode == 'tf':
x /= 127.5
x -= 1.
return x
if mode == 'torch':
x /= 255.
mean = [0.485, 0.456, 0.406]
std = [0.229, 0.224, 0.225]
else:
if data_format == 'channels_first':
# 'RGB'->'BGR'
if x.ndim == 3:
x = x[::-1, ...]
else:
x = x[:, ::-1, ...]
else:
# 'RGB'->'BGR'
x = x[..., ::-1]
mean = [103.939, 116.779, 123.68]
std = None
# Zero-center by mean pixel
if data_format == 'channels_first':
if x.ndim == 3:
x[0, :, :] -= mean[0]
x[1, :, :] -= mean[1]
x[2, :, :] -= mean[2]
if std is not None:
x[0, :, :] /= std[0]
x[1, :, :] /= std[1]
x[2, :, :] /= std[2]
else:
x[:, 0, :, :] -= mean[0]
x[:, 1, :, :] -= mean[1]
x[:, 2, :, :] -= mean[2]
if std is not None:
x[:, 0, :, :] /= std[0]
x[:, 1, :, :] /= std[1]
x[:, 2, :, :] /= std[2]
else:
x[..., 0] -= mean[0]
x[..., 1] -= mean[1]
x[..., 2] -= mean[2]
if std is not None:
x[..., 0] /= std[0]
x[..., 1] /= std[1]
x[..., 2] /= std[2]
return x
def _preprocess_symbolic_input(x, data_format, mode, **kwargs):
"""Preprocesses a tensor encoding a batch of images.
# Arguments
x: Input tensor, 3D or 4D.
data_format: Data format of the image tensor.
mode: One of "caffe", "tf" or "torch".
- caffe: will convert the images from RGB to BGR,
then will zero-center each color channel with
respect to the ImageNet dataset,
without scaling.
- tf: will scale pixels between -1 and 1,
sample-wise.
- torch: will scale pixels between 0 and 1 and then
will normalize each channel with respect to the
ImageNet dataset.
# Returns
Preprocessed tensor.
"""
if mode == 'tf':
x /= 127.5
x -= 1.
return x
if mode == 'torch':
x /= 255.
mean = [0.485, 0.456, 0.406]
std = [0.229, 0.224, 0.225]
else:
if data_format == 'channels_first':
# 'RGB'->'BGR'
if backend.ndim(x) == 3:
x = x[::-1, ...]
else:
x = x[:, ::-1, ...]
else:
# 'RGB'->'BGR'
x = x[..., ::-1]
mean = [103.939, 116.779, 123.68]
std = None
mean_tensor = backend.constant(-np.array(mean))
# Zero-center by mean pixel
if backend.dtype(x) != backend.dtype(mean_tensor):
x = backend.bias_add(
x, backend.cast(mean_tensor, backend.dtype(x)),
data_format=data_format)
else:
x = backend.bias_add(x, mean_tensor, data_format)
if std is not None:
x /= std
return x
def preprocess_input(x, data_format=None, mode='caffe', **kwargs):
"""Preprocesses a tensor or Numpy array encoding a batch of images.
# Arguments
x: Input Numpy or symbolic tensor, 3D or 4D.
The preprocessed data is written over the input data
if the data types are compatible. To avoid this
behaviour, `numpy.copy(x)` can be used.
data_format: Data format of the image tensor/array.
mode: One of "caffe", "tf" or "torch".
- caffe: will convert the images from RGB to BGR,
then will zero-center each color channel with
respect to the ImageNet dataset,
without scaling.
- tf: will scale pixels between -1 and 1,
sample-wise.
- torch: will scale pixels between 0 and 1 and then
will normalize each channel with respect to the
ImageNet dataset.
# Returns
Preprocessed tensor or Numpy array.
# Raises
ValueError: In case of unknown `data_format` argument.
"""
if data_format is None:
data_format = backend.image_data_format()
if data_format not in {'channels_first', 'channels_last'}:
raise ValueError('Unknown data_format ' + str(data_format))
if isinstance(x, np.ndarray):
return _preprocess_numpy_input(x, data_format=data_format,
mode=mode, **kwargs)
else:
return _preprocess_symbolic_input(x, data_format=data_format,
mode=mode, **kwargs)
def decode_predictions(preds, top=5, **kwargs):
"""Decodes the prediction of an ImageNet model.
# Arguments
preds: Numpy tensor encoding a batch of predictions.
top: Integer, how many top-guesses to return.
# Returns
A list of lists of top class prediction tuples
`(class_name, class_description, score)`.
One list of tuples per sample in batch input.
# Raises
ValueError: In case of invalid shape of the `pred` array
(must be 2D).
"""
global CLASS_INDEX
if len(preds.shape) != 2 or preds.shape[1] != 1000:
raise ValueError('`decode_predictions` expects '
'a batch of predictions '
'(i.e. a 2D array of shape (samples, 1000)). '
'Found array with shape: ' + str(preds.shape))
if CLASS_INDEX is None:
fpath = keras_utils.get_file(
'imagenet_class_index.json',
CLASS_INDEX_PATH,
cache_subdir='models',
file_hash='c2c37ea517e94d9795004a39431a14cb')
with open(fpath) as f:
CLASS_INDEX = json.load(f)
results = []
for pred in preds:
top_indices = pred.argsort()[-top:][::-1]
result = [tuple(CLASS_INDEX[str(i)]) + (pred[i],) for i in top_indices]
result.sort(key=lambda x: x[2], reverse=True)
results.append(result)
return results
def _obtain_input_shape(input_shape,
default_size,
min_size,
data_format,
require_flatten,
weights=None):
"""Internal utility to compute/validate a model's input shape.
# Arguments
input_shape: Either None (will return the default network input shape),
or a user-provided shape to be validated.
default_size: Default input width/height for the model.
min_size: Minimum input width/height accepted by the model.
data_format: Image data format to use.
require_flatten: Whether the model is expected to
be linked to a classifier via a Flatten layer.
weights: One of `None` (random initialization)
or 'imagenet' (pre-training on ImageNet).
If weights='imagenet' input channels must be equal to 3.
# Returns
An integer shape tuple (may include None entries).
# Raises
ValueError: In case of invalid argument values.
"""
if weights != 'imagenet' and input_shape and len(input_shape) == 3:
if data_format == 'channels_first':
if input_shape[0] not in {1, 3}:
warnings.warn(
'This model usually expects 1 or 3 input channels. '
'However, it was passed an input_shape with ' +
str(input_shape[0]) + ' input channels.')
default_shape = (input_shape[0], default_size, default_size)
else:
if input_shape[-1] not in {1, 3}:
warnings.warn(
'This model usually expects 1 or 3 input channels. '
'However, it was passed an input_shape with ' +
str(input_shape[-1]) + ' input channels.')
default_shape = (default_size, default_size, input_shape[-1])
else:
if data_format == 'channels_first':
default_shape = (3, default_size, default_size)
else:
default_shape = (default_size, default_size, 3)
if weights == 'imagenet' and require_flatten:
if input_shape is not None:
if input_shape != default_shape:
raise ValueError('When setting `include_top=True` '
'and loading `imagenet` weights, '
'`input_shape` should be ' +
str(default_shape) + '.')
return default_shape
if input_shape:
if data_format == 'channels_first':
if input_shape is not None:
if len(input_shape) != 3:
raise ValueError(
'`input_shape` must be a tuple of three integers.')
if input_shape[0] != 3 and weights == 'imagenet':
raise ValueError('The input must have 3 channels; got '
'`input_shape=' + str(input_shape) + '`')
if ((input_shape[1] is not None and input_shape[1] < min_size) or
(input_shape[2] is not None and input_shape[2] < min_size)):
raise ValueError('Input size must be at least ' +
str(min_size) + 'x' + str(min_size) +
'; got `input_shape=' +
str(input_shape) + '`')
else:
if input_shape is not None:
if len(input_shape) != 3:
raise ValueError(
'`input_shape` must be a tuple of three integers.')
if input_shape[-1] != 3 and weights == 'imagenet':
raise ValueError('The input must have 3 channels; got '
'`input_shape=' + str(input_shape) + '`')
if ((input_shape[0] is not None and input_shape[0] < min_size) or
(input_shape[1] is not None and input_shape[1] < min_size)):
raise ValueError('Input size must be at least ' +
str(min_size) + 'x' + str(min_size) +
'; got `input_shape=' +
str(input_shape) + '`')
else:
if require_flatten:
input_shape = default_shape
else:
if data_format == 'channels_first':
input_shape = (3, None, None)
else:
input_shape = (None, None, 3)
if require_flatten:
if None in input_shape:
raise ValueError('If `include_top` is True, '
'you should specify a static `input_shape`. '
'Got `input_shape=' + str(input_shape) + '`')
return input_shape
def correct_pad(backend, inputs, kernel_size):
"""Returns a tuple for zero-padding for 2D convolution with downsampling.
# Arguments
input_size: An integer or tuple/list of 2 integers.
kernel_size: An integer or tuple/list of 2 integers.
# Returns
A tuple.
"""
img_dim = 2 if backend.image_data_format() == 'channels_first' else 1
input_size = backend.int_shape(inputs)[img_dim:(img_dim + 2)]
if isinstance(kernel_size, int):
kernel_size = (kernel_size, kernel_size)
if input_size[0] is None:
adjust = (1, 1)
else:
adjust = (1 - input_size[0] % 2, 1 - input_size[1] % 2)
correct = (kernel_size[0] // 2, kernel_size[1] // 2)
return ((correct[0] - adjust[0], correct[0]),
(correct[1] - adjust[1], correct[1]))
