How to extract and save images from tensorboard event summary?

Question

Given a tensorflow event file, how can I extract images corresponding to a specific tag, and then save them to disk in a common format e.g. .png?

Answer 1

If you are using TensorFlow 2, this works nicely

from collections import defaultdict, namedtuple
from typing import List
import tensorflow as tf


TensorBoardImage = namedtuple("TensorBoardImage", ["topic", "image", "cnt"])


def extract_images_from_event(event_filename: str, image_tags: List[str]):
    topic_counter = defaultdict(lambda: 0)

    serialized_examples = tf.data.TFRecordDataset(event_filename)
    for serialized_example in serialized_examples:
        event = event_pb2.Event.FromString(serialized_example.numpy())
        for v in event.summary.value:
            if v.tag in image_tags:

                if v.HasField('tensor'):  # event for images using tensor field
                    s = v.tensor.string_val[2]  # first elements are W and H

                    tf_img = tf.image.decode_image(s)  # [H, W, C]
                    np_img = tf_img.numpy()

                    topic_counter[v.tag] += 1

                    cnt = topic_counter[v.tag]
                    tbi = TensorBoardImage(topic=v.tag, image=np_img, cnt=cnt)

                    yield tbi

Although, 'v' has an image field, it is empty.

I used

    tf.summary.image("topic", img)

to add the images to the event file.