TFRecord产生的背景：
一般情况下数据集经常分为 train, test 文件夹，文件夹内部往往会存着成千上万的图片或文本等文件，这些文件被散列存着，不仅占用磁盘空间，读取的时候频繁访问磁盘，会非常慢。TFRecord内部使用了“Protocol Buffer”二进制数据编码方案，它只占用一个内存块，只需要一次性加载一个二进制文件的方式即可，简单，快速，尤其对大型训练数据很友好。而且当我们的训练数据量比较大的时候，可以将数据分成多个TFRecord文件，来提高处理效率
下面分为3个方面说明其如何使用：代码结构，TFRecord创建，TFRecord读取
1、代码结构：
image.png
2、TFRecord创建
#coding=utf-8
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
from datetime import datetime
import os
import random
import sys
import threading
import numpy as np
import tensorflow as tf
tf.app.flags.DEFINE_string('train_directory', './flower_photos/',
'Training data directory')
tf.app.flags.DEFINE_string('validation_directory', './flower_photos/',
'Validation data directory')
tf.app.flags.DEFINE_string('output_directory', './data/',
'Output data directory')
tf.app.flags.DEFINE_integer('train_shards', 2,
'Number of shards in training TFRecord files.')
tf.app.flags.DEFINE_integer('validation_shards', 0,
'Number of shards in validation TFRecord files.')
tf.app.flags.DEFINE_integer('num_threads', 2,
'Number of threads to preprocess the images.')
# The labels file contains a list of valid labels are held in this file.
# Assumes that the file contains entries as such:
# dog
# cat
# flower
# where each line corresponds to a label. We map each label contained in
# the file to an integer corresponding to the line number starting from 0.
tf.app.flags.DEFINE_string('labels_file', './flower_label.txt', 'Labels file')
FLAGS = tf.app.flags.FLAGS
def _int64_feature(value):
"""Wrapper for inserting int64 features into Example proto."""
if not isinstance(value, list):
value = [value]
return tf.train.Feature(int64_list=tf.train.Int64List(value=value))
def _bytes_feature(value):
"""Wrapper for inserting bytes features into Example proto."""
return tf.train.Feature(bytes_list=tf.train.BytesList(value=[value]))
def _convert_to_example(filename, image_buffer, label, text, height, width):
"""Build an Example proto for an example.
Args:
filename: string, path to an image file, e.g., '/path/to/example.JPG'
image_buffer: string, JPEG encoding of RGB image
label: integer, identifier for the ground truth for the network
text: string, unique human-readable, e.g. 'dog'
height: integer, image height in pixels
width: integer, image width in pixels
Returns:
Example proto
"""
colorspace = 'RGB'
channels = 3
image_format = 'JPEG'
example = tf.train.Example(features=tf.train.Features(feature={
'image/height': _int64_feature(height),
'image/width': _int64_feature(width),
'image/colorspace': _bytes_feature(tf.compat.as_bytes(colorspace)),
'image/channels': _int64_feature(channels),
'image/class/label': _int64_feature(label),
'image/class/text': _bytes_feature(tf.compat.as_bytes(text)),
'image/format': _bytes_feature(tf.compat.as_bytes(image_format)),
'image/filename': _bytes_feature(tf.compat.as_bytes(os.path.basename(filename))),
'image/encoded': _bytes_feature(tf.compat.as_bytes(image_buffer))}))
return example
class ImageCoder(object):
"""Helper class that provides TensorFlow image coding utilities."""
def __init__(self):
# Create a single Session to run all image coding calls.
self._sess = tf.Session()
# Initializes function that converts PNG to JPEG data.
self._png_data = tf.placeholder(dtype=tf.string)
image = tf.image.decode_png(self._png_data, channels=3)
self._png_to_jpeg = tf.image.encode_jpeg(image, format='rgb', quality=100)
# Initializes function that decodes RGB JPEG data.
self._decode_jpeg_data = tf.placeholder(dtype=tf.string)
self._decode_jpeg = tf.image.decode_jpeg(self._decode_jpeg_data, channels=3)
def png_to_jpeg(self, image_data):
return self._sess.run(self._png_to_jpeg,
feed_dict={self._png_data: image_data})
def decode_jpeg(self, image_data):
image = self._sess.run(self._decode_jpeg,
feed_dict={self._decode_jpeg_data: image_data})
assert len(image.shape) == 3
assert image.shape[2] == 3
return image
def _is_png(filename):
"""Determine if a file contains a PNG format image.
Args:
filename: string, path of the image file.
Returns:
boolean indicating if the image is a PNG.
"""
return '.png' in filename
def _process_image(filename, coder):
"""Process a single image file.
Args:
filename: string, path to an image file e.g., '/path/to/example.JPG'.
coder: instance of ImageCoder to provide TensorFlow image coding utils.
Returns:
image_buffer: string, JPEG encoding of RGB image.
height: integer, image height in pixels.
width: integer, image width in pixels.
"""
# Read the image file.
with tf.gfile.FastGFile(filename, 'rb') as f:
image_data = f.read()
# Convert any PNG to JPEG's for consistency.
if _is_png(filename):
print('Converting PNG to JPEG for %s' % filename)
image_data = coder.png_to_jpeg(image_data)
# Decode the RGB JPEG.
image = coder.decode_jpeg(image_data)
# Check that image converted to RGB
assert len(image.shape) == 3
height = image.shape[0]
width = image.shape[1]
assert image.shape[2] == 3
return image_data, height, width
def _process_image_files_batch(coder, thread_index, ranges, name, filenames,
texts, labels, num_shards):
"""Processes and saves list of images as TFRecord in 1 thread.
Args:
coder: instance of ImageCoder to provide TensorFlow image coding utils.
thread_index: integer, unique batch to run index is within [0, len(ranges)).
ranges: list of pairs of integers specifying ranges of each batches to
analyze in parallel.
name: string, unique identifier specifying the data set
filenames: list of strings; each string is a path to an image file
texts: list of strings; each string is human readable, e.g. 'dog'
labels: list of integer; each integer identifies the ground truth
num_shards: integer number of shards for this data set.
"""
# Each thread produces N shards where N = int(num_shards / num_threads).
# For instance, if num_shards = 128, and the num_threads = 2, then the first
# thread would produce shards [0, 64).
num_threads = len(ranges)
assert not num_shards % num_threads
num_shards_per_batch = int(num_shards / num_threads)
shard_ranges = np.linspace(ranges[thread_index][0],
ranges[thread_index][1],
num_shards_per_batch + 1).astype(int)
num_files_in_thread = ranges[thread_index][1] - ranges[thread_index][0]
counter = 0
for s in range(num_shards_per_batch):
# Generate a sharded version of the file name, e.g. 'train-00002-of-00010'
shard = thread_index * num_shards_per_batch + s
output_filename = '%s-%.5d-of-%.5d.tfrecord' % (name, shard, num_shards)
output_file = os.path.join(FLAGS.output_directory, output_filename)
writer = tf.python_io.TFRecordWriter(output_file)
shard_counter = 0
files_in_shard = np.arange(shard_ranges[s], shard_ranges[s + 1], dtype=int)
for i in files_in_shard:
filename = filenames[i]
label = labels[i]
text = texts[i]
image_buffer, height, width = _process_image(filename, coder)
example = _convert_to_example(filename, image_buffer, label,
text, height, width)
writer.write(example.SerializeToString())
shard_counter += 1
counter += 1
if not counter % 1000:
print('%s [thread %d]: Processed %d of %d images in thread batch.' %
(datetime.now(), thread_index, counter, num_files_in_thread))
sys.stdout.flush()
writer.close()
print('%s [thread %d]: Wrote %d images to %s' %
(datetime.now(), thread_index, shard_counter, output_file))
sys.stdout.flush()
shard_counter = 0
print('%s [thread %d]: Wrote %d images to %d shards.' %
(datetime.now(), thread_index, counter, num_files_in_thread))
sys.stdout.flush()
def _process_image_files(name, filenames, texts, labels, num_shards):
"""Process and save list of images as TFRecord of Example protos.
Args:
name: string, unique identifier specifying the data set
filenames: list of strings; each string is a path to an image file
texts: list of strings; each string is human readable, e.g. 'dog'
labels: list of integer; each integer identifies the ground truth
num_shards: integer number of shards for this data set.
"""
assert len(filenames) == len(texts)
assert len(filenames) == len(labels)
# Break all images into batches with a [ranges[i][0], ranges[i][1]].
spacing = np.linspace(0, len(filenames), FLAGS.num_threads + 1).astype(np.int)
ranges = []
for i in range(len(spacing) - 1):
ranges.append([spacing[i], spacing[i+1]])
# Launch a thread for each batch.
print('Launching %d threads for spacings: %s' % (FLAGS.num_threads, ranges))
sys.stdout.flush()
# Create a mechanism for monitoring when all threads are finished.
coord = tf.train.Coordinator()
# Create a generic TensorFlow-based utility for converting all image codings.
coder = ImageCoder()
threads = []
for thread_index in range(len(ranges)):
args = (coder, thread_index, ranges, name, filenames,
texts, labels, num_shards)
t = threading.Thread(target=_process_image_files_batch, args=args)
t.start()
threads.append(t)
# Wait for all the threads to terminate.
coord.join(threads)
print('%s: Finished writing all %d images in data set.' %
(datetime.now(), len(filenames)))
sys.stdout.flush()
def _find_image_files(data_dir, labels_file):
"""Build a list of all images files and labels in the data set.
Args:
data_dir: string, path to the root directory of images.
Assumes that the image data set resides in JPEG files located in
the following directory structure.
data_dir/dog/another-image.JPEG
data_dir/dog/my-image.jpg
where 'dog' is the label associated with these images.
labels_file: string, path to the labels file.
The list of valid labels are held in this file. Assumes that the file
contains entries as such:
dog
cat
flower
where each line corresponds to a label. We map each label contained in
the file to an integer starting with the integer 0 corresponding to the
label contained in the first line.
Returns:
filenames: list of strings; each string is a path to an image file.
texts: list of strings; each string is the class, e.g. 'dog'
labels: list of integer; each integer identifies the ground truth.
"""
print('目标文件夹位置： %s.' % data_dir)
unique_labels = [l.strip() for l in tf.gfile.FastGFile(
labels_file, 'r').readlines()]
labels = []
filenames = []
texts = []
# Leave label index 0 empty as a background class.
label_index = 1
# Construct the list of JPEG files and labels.
for text in unique_labels:
jpeg_file_path = '%s/%s/*' % (data_dir, text)
try:
matching_files = tf.gfile.Glob(jpeg_file_path)
except:
print (jpeg_file_path)
continue
labels.extend([label_index] * len(matching_files))
texts.extend([text] * len(matching_files))
filenames.extend(matching_files)
label_index += 1
# Shuffle the ordering of all image files in order to guarantee
# random ordering of the images with respect to label in the
# saved TFRecord files. Make the randomization repeatable.
shuffled_index = list(range(len(filenames)))
random.seed(12345)
random.shuffle(shuffled_index)
filenames = [filenames[i] for i in shuffled_index]
texts = [texts[i] for i in shuffled_index]
labels = [labels[i] for i in shuffled_index]
print('Found %d JPEG files across %d labels inside %s.' %
(len(filenames), len(unique_labels), data_dir))
return filenames, texts, labels
def _process_dataset(name, directory, num_shards, labels_file):
"""Process a complete data set and save it as a TFRecord.
Args:
name: string, unique identifier specifying the data set.
directory: string, root path to the data set.
num_shards: integer number of shards for this data set.
labels_file: string, path to the labels file.
"""
filenames, texts, labels = _find_image_files(directory, labels_file)
_process_image_files(name, filenames, texts, labels, num_shards)
def main(unused_argv):
assert not FLAGS.train_shards % FLAGS.num_threads, (
'在测试集中：线程数量应用建立文件个数想对应')
assert not FLAGS.validation_shards % FLAGS.num_threads, (
'在测试集中：线程数量应用建立文件个数想对应')
print('生成数据文件夹 %s' % FLAGS.output_directory)
# Run it!
_process_dataset('train', FLAGS.train_directory,
FLAGS.train_shards, FLAGS.labels_file)
"""
_process_dataset('validation', FLAGS.validation_directory,
FLAGS.validation_shards, FLAGS.labels_file)
"""
if __name__ == '__main__':
tf.app.run()
TFRecord数据的读取：
def read_and_decode(filename_queue):
reader = tf.TFRecordReader()
_, serialized_example = reader.read(filename_queue)
features = tf.parse_single_example(serialized_example, features = {
"image/encoded": tf.FixedLenFeature([], tf.string),
"image/height": tf.FixedLenFeature([], tf.int64),
"image/width": tf.FixedLenFeature([], tf.int64),
"image/filename": tf.FixedLenFeature([], tf.string),
"image/class/label": tf.FixedLenFeature([], tf.int64),})
image_encoded = features["image/encoded"]
image_raw = tf.image.decode_jpeg(image_encoded, channels=3)
image_object = _image_object()
image_object.image = tf.image.resize_image_with_crop_or_pad(image_raw, IMAGE_SIZE, IMAGE_SIZE)
image_object.height = features["image/height"]
image_object.width = features["image/width"]
image_object.filename = features["image/filename"]
image_object.label = tf.cast(features["image/class/label"], tf.int64)
return image_object
def flower_input(if_random = True, if_training = True):
if(if_training):
filenames = [os.path.join(DATA_DIR, "train-0000%d-of-00002.tfrecord" % i) for i in range(0, 2)]
else:
filenames = [os.path.join(DATA_DIR, "eval-0000%d-of-00002.tfrecord" % i) for i in range(0, 2)]
for f in filenames:
if not tf.gfile.Exists(f):
raise ValueError("Failed to find file: " + f)
filename_queue = tf.train.string_input_producer(filenames)
image_object = read_and_decode(filename_queue)
image = tf.image.per_image_standardization(image_object.image)
# image = image_object.image
# image = tf.image.adjust_gamma(tf.cast(image_object.image, tf.float32), gamma=1, gain=1) # Scale image to (0, 1)
label = image_object.label
filename = image_object.filename
if(if_random):
min_fraction_of_examples_in_queue = 0.4
min_queue_examples = int(TRAINING_SET_SIZE * min_fraction_of_examples_in_queue)
print("Filling queue with %d images before starting to train. " "This will take a few minutes." % min_queue_examples)
num_preprocess_threads = 1
image_batch, label_batch, filename_batch = tf.train.shuffle_batch(
[image, label, filename],
batch_size = BATCH_SIZE,
num_threads = num_preprocess_threads,
capacity = min_queue_examples + 3 * BATCH_SIZE,
min_after_dequeue = min_queue_examples)
return image_batch, label_batch, filename_batch
else:
image_batch, label_batch, filename_batch = tf.train.batch(
[image, label, filename],
batch_size = BATCH_SIZE,
num_threads = 1)
return image_batch, label_batch, filename_batch
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