Extract images from a rosbag.

bag_to_images.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# Copyright 2016 Massachusetts Institute of Technology

"""Extract images from a rosbag.
"""

import os
import argparse

import cv2

import rosbag
from sensor_msgs.msg import Image
from cv_bridge import CvBridge

def main():
    """Extract a folder of images from a rosbag.
    """
    parser = argparse.ArgumentParser(description="Extract images from a ROS bag.")
    parser.add_argument("bag_file", help="Input ROS bag.")
    parser.add_argument("output_dir", help="Output directory.")
    parser.add_argument("image_topic", help="Image topic.")

    args = parser.parse_args()

    print "Extract images from %s on topic %s into %s" % (args.bag_file,
                                                          args.image_topic, args.output_dir)

    bag = rosbag.Bag(args.bag_file, "r")
    bridge = CvBridge()
    count = 0
    for topic, msg, t in bag.read_messages(topics=[args.image_topic]):
        cv_img = bridge.imgmsg_to_cv2(msg, desired_encoding="passthrough")

        cv2.imwrite(os.path.join(args.output_dir, "frame%06i.png" % count), cv_img)
        print "Wrote image %i" % count

        count += 1

    bag.close()

    return

if __name__ == '__main__':
    main()

Hello @wngreene, I have run the code and it occurs this error: TypeError: init() takes 2 positional arguments but 3 were given. Do you know how to solve this problem?
Thank you!

THX! very useful!

This method doesn't work on compressed messages. Tweaking this code with only subscriber and playing the rosbag can work

Pretty cool:)

I'm trying to import rosbag, but it can't find the module, can someone share how you installed the module?

how can i use cv_bridge in anaconda(windows 10)? i am getting error like this
ERROR: Could not find a version that satisfies the requirement cvbridge (from versions: none)
ERROR: No matching distribution found for cvbridge

Thank you for the share

@wngreene do you have a version of script for ros2 Humble? Thank you.

@monajalal If you have a script for ros2 Humble, do share it! Thank You!