import json
from keras.utils.data_utils import get_file
from keras import backend as K
CLASS_INDEX = None
CLASS_INDEX_PATH = 'https://s3.amazonaws.com/deep-learning-models/image-models/imagenet_class_index.json'
def preprocess_input(x, data_format=None):
"""Preprocesses a tensor encoding a batch of images.
# Arguments
x: input Numpy tensor, 4D.
data_format: data format of the image tensor.
# Returns
Preprocessed tensor.
"""
if data_format is None:
data_format = K.image_data_format()
assert data_format in {'channels_last', 'channels_first'}
if data_format == 'channels_first':
# 'RGB'->'BGR'
x = x[:, ::-1, :, :]
# Zero-center by mean pixel
x[:, 0, :, :] -= 103.939
x[:, 1, :, :] -= 116.779
x[:, 2, :, :] -= 123.68
else:
# 'RGB'->'BGR'
x = x[:, :, :, ::-1]
# Zero-center by mean pixel
x[:, :, :, 0] -= 103.939
x[:, :, :, 1] -= 116.779
x[:, :, :, 2] -= 123.68
return x
def decode_predictions(preds, top=5):
"""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 = get_file('imagenet_class_index.json',
CLASS_INDEX_PATH,
cache_subdir='models')
CLASS_INDEX = json.load(open(fpath))
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,
include_top):
"""Internal utility to compute/validate an ImageNet 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.
include_top: whether the model is expected to
be linked to a classifier via a Flatten layer.
# Returns
An integer shape tuple (may include None entries).
# Raises
ValueError: in case of invalid argument values.
"""
if data_format == 'channels_first':
default_shape = (3, default_size, default_size)
else:
default_shape = (default_size, default_size, 3)
if include_top:
if input_shape is not None:
if input_shape != default_shape:
raise ValueError('When setting`include_top=True`, '
'`input_shape` should be ' + str(default_shape) + '.')
input_shape = default_shape
else:
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:
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:
input_shape = (3, None, None)
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:
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:
input_shape = (None, None, 3)
return input_shape
