Accessing filename from file queue in Tensor Flow

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梦如初夏
梦如初夏 2021-02-20 10:11

I have a directory of images, and a separate file matching image filenames to labels. So the directory of images has files like \'train/001.jpg\' and the labeling file looks lik

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  • 2021-02-20 10:34

    Here's what I was able to do.

    I first shuffled the filenames and matched the labels to them in Python:

    np.random.shuffle(filenames)
    labels = [label_dict[f] for f in filenames]
    

    Then created a string_input_producer for the filenames with shuffle off, and a FIFO for labels:

    lv = tf.constant(labels)
    label_fifo = tf.FIFOQueue(len(filenames),tf.int32, shapes=[[]])
    file_fifo = tf.train.string_input_producer(filenames, shuffle=False, capacity=len(filenames))
    label_enqueue = label_fifo.enqueue_many([lv])
    

    Then to read the image I could use a WholeFileReader and to get the label I could dequeue the fifo:

    reader = tf.WholeFileReader()
    image = tf.image.decode_jpeg(value, channels=3)
    image.set_shape([128,128,3])
    result.uint8image = image
    result.label = label_fifo.dequeue()
    

    And generate the batches as follows:

    min_fraction_of_examples_in_queue = 0.4
    min_queue_examples = int(num_examples_per_epoch *
                             min_fraction_of_examples_in_queue)
    num_preprocess_threads = 16
    images, label_batch = tf.train.shuffle_batch(
      [result.uint8image, result.label],
      batch_size=FLAGS.batch_size,
      num_threads=num_preprocess_threads,
      capacity=min_queue_examples + 3 * FLAGS.batch_size,
      min_after_dequeue=min_queue_examples)
    
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  • 2021-02-20 10:43

    I used this:

     filename = filename.strip().decode('ascii')
    
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  • 2021-02-20 10:44

    Given that your data is not too large for you to supply the list of filenames as a python array, I'd suggest just doing the preprocessing in Python. Create two lists (same order) of the filenames and the labels, and insert those into either a randomshufflequeue or a queue, and dequeue from that. If you want the "loops infinitely" behavior of the string_input_producer, you could re-run the 'enqueue' at the start of every epoch.

    A very toy example:

    import tensorflow as tf
    
    f = ["f1", "f2", "f3", "f4", "f5", "f6", "f7", "f8"]
    l = ["l1", "l2", "l3", "l4", "l5", "l6", "l7", "l8"]
    
    fv = tf.constant(f)
    lv = tf.constant(l)
    
    rsq = tf.RandomShuffleQueue(10, 0, [tf.string, tf.string], shapes=[[],[]])
    do_enqueues = rsq.enqueue_many([fv, lv])
    
    gotf, gotl = rsq.dequeue()
    
    with tf.Session() as sess:
        sess.run(tf.initialize_all_variables())
        tf.train.start_queue_runners(sess=sess)
        sess.run(do_enqueues)
        for i in xrange(2):
            one_f, one_l = sess.run([gotf, gotl])
            print "F: ", one_f, "L: ", one_l
    

    The key is that you're effectively enqueueing pairs of filenames/labels when you do the enqueue, and those pairs are returned by the dequeue.

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  • 2021-02-20 10:46

    Another suggestion is to save your data in TFRecord format. In this case you would be able to save all images and all labels in the same file. For a big number of files it gives a lot of advantages:

    • can store data and labels at the same place
    • data is allocated at one place (no need to remember various directories)
    • if there are many files (images), opening/closing a file is time consuming. Seeking the location of the file from ssd/hdd also takes time
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  • 2021-02-20 10:52

    There is tf.py_func() you could utilize to implement a mapping from file path to label.

    files = gfile.Glob(data_pattern)
    filename_queue = tf.train.string_input_producer(
    files, num_epochs=num_epochs, shuffle=True) #  list of files to read
    
    def extract_label(s):
        # path to label logic for cat&dog dataset
        return 0 if os.path.basename(str(s)).startswith('cat') else 1
    
    def read(filename_queue):
      key, value = reader.read(filename_queue)
      image = tf.image.decode_jpeg(value, channels=3)
      image = tf.cast(image, tf.float32)
      image = tf.image.resize_image_with_crop_or_pad(image, width, height)
      label = tf.cast(tf.py_func(extract_label, [key], tf.int64), tf.int32)
      label = tf.reshape(label, [])
    
    training_data = [read(filename_queue) for _ in range(num_readers)]
    
    ...
    
    tf.train.shuffle_batch_join(training_data, ...)
    
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