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解决错误：No module named 'Cryptodome' 和错误rosbag.bag.ROSBagException: unsupported compression type: lz4

文章目录：

1 说明遇到问题的场景
2 解决错误：No module named 'Cryptodome'
3 解决错误：rosbag.bag.ROSBagException: unsupported compression type: lz4
- 3.1 尝试解决方式一
- 3.2 尝试解决方式二
- 3.3 最终的问题解决方法
- 3.4 解决错误：ImportError: dynamic module does not define module export function (PyInit_cv_bridge_boost)
4 两种提取雷达数据包中图片的方式
- 4.1 使用roslaunch提取雷达数据包中的图片
- 4.2 使用python库包rogbag、cv_bridge、cv2提取
- 4.3 两种提取雷达数据包中图片的结果对比

1 说明遇到问题的场景

我的目的是：

提取雷达数据包：2020-08-04-16-22-48.bag中的图片数据
使用python库包：rosbag、cv2、cv_bridge进行提取工作

提取代码如下：

import rosbag
import cv2
from cv_bridge import CvBridgebag_file = '/home/shl/2020-08-04-16-22-48.bag'
bag = rosbag.Bag(bag_file, "r")bridge = CvBridge()
bag_data_imgs = bag.read_messages('/ns1/usb_cam/image_raw')def extract_imgs():i = 1for topic, msg, t in bag_data_imgs:cv_image = bridge.imgmsg_to_cv2(msg, "bgr8")print(type(cv_image))  # <type 'numpy.ndarray'>#cv2.imshow("Image window", cv_image)#cv2.waitKey(3)cv2.imwrite("./extract_images/%05d.png".format(i), cv_image)i+=1if __name__ == '__main__':extract_imgs()

2 解决错误：No module named ‘Cryptodome’

1、程序运行后报错：ModuleNotFoundError: No module named 'Cryptodome'

解决方式：

pip install pycryptodomex

2、后面可能又报错：ModuleNotFoundError: No module named 'gnupg'

解决方式：

pip install gnupg

3 解决错误：rosbag.bag.ROSBagException: unsupported compression type: lz4

1、上面的两个错误刚解决，运行程序之后又报错：rosbag.bag.ROSBagException: unsupported compression type: lz4

(yolov4) shl@zhihui-mint:~/extract_rosbag_data$ python extract_bag_images.py
Failed to load Python extension for LZ4 support. LZ4 compression will not be available.
Traceback (most recent call last):File "extract_bag_images.py", line 24, in <module>extract_imgs()File "extract_bag_images.py", line 14, in extract_imgsfor topic, msg, t in bag_data_imgs:File "/opt/ros/melodic/lib/python2.7/dist-packages/rosbag/bag.py", line 2699, in read_messagesyield self.seek_and_read_message_data_record((entry.chunk_pos, entry.offset), raw, return_connection_header)File "/opt/ros/melodic/lib/python2.7/dist-packages/rosbag/bag.py", line 2833, in seek_and_read_message_data_recordraise ROSBagException('unsupported compression type: %s' % chunk_header.compression)
rosbag.bag.ROSBagException: unsupported compression type: lz4
(yolov4) shl@zhihui-mint:~/extract_rosbag_data$

3.1 尝试解决方式一

错误信息：无法加载LZ4支持的Python扩展。 LZ4压缩将不可用，这里说这是由于ROS库造成的问题，但遇到的只是警告，我这里直接是错误，用处也不是很大

尝试解决方式1（无效）：

pip install lz4

3.2 尝试解决方式二

1、我先使用rosbag查看一下bag文件的一些信息：

rosbag info 2020-08-04-16-22-48.bag

(base) shl@zhihui-mint:~/extract_rosbag_data$ rosbag info 2020-08-04-16-22-48.bag
path:         2020-08-04-16-22-48.bag
version:      2.0
duration:     5:14s (314s)
start:        Aug 04 2020 16:22:49.08 (1596529369.08)
end:          Aug 04 2020 16:28:03.36 (1596529683.36)
size:         6.8 GB
messages:     7439
compression:  lz4 [3126/3126 chunks; 84.80%]
uncompressed: 8.0 GB @ 26.2 MB/s
compressed:   6.8 GB @ 22.2 MB/s (84.80%)
types:        sensor_msgs/Image       [060021388200f6f0f447d0fcd9c64743]sensor_msgs/PointCloud2 [1158d486dd51d683ce2f1be655c3c181]
topics:       /ns1/usb_cam/image_raw   3125 msgs    : sensor_msgs/Image      /radar_projection        4314 msgs    : sensor_msgs/PointCloud2
(base) shl@zhihui-mint:~/extract_rosbag_data$

从上面可以看到2020-08-04-16-22-48.bag的压缩方式是：lz4

2、如果我们尝试把2020-08-04-16-22-48.bag解压后，再读取看是否有问题

rosbag decompress 2020-08-04-16-22-48.bag --output-dir ./extract_images/

3、让我们再来看一下解压后的bag文件的信息：


(base) shl@zhihui-mint:~/extract_rosbag_data/extract_images$ rosbag info 2020-08-04-16-22-48.bag
path:        2020-08-04-16-22-48.bag
version:     2.0
duration:    5:14s (314s)
start:       Aug 04 2020 16:22:49.08 (1596529369.08)
end:         Aug 04 2020 16:28:03.36 (1596529683.36)
size:        8.0 GB
messages:    7439
compression: none [3126/3126 chunks]
types:       sensor_msgs/Image       [060021388200f6f0f447d0fcd9c64743]sensor_msgs/PointCloud2 [1158d486dd51d683ce2f1be655c3c181]
topics:      /ns1/usb_cam/image_raw   3125 msgs    : sensor_msgs/Image      /radar_projection        4314 msgs    : sensor_msgs/PointCloud2
(base) shl@zhihui-mint:~/extract_rosbag_data/extract_images$

4、然后再读取一次，结果又报错：ImportError: dynamic module does not define module export function (PyInit_cv_bridge_boost)


(base) shl@zhihui-mint:~/extract_rosbag_data$ python extract_bag_images.py
Failed to load Python extension for LZ4 support. LZ4 compression will not be available.
Traceback (most recent call last):File "extract_bag_images.py", line 24, in <module>extract_imgs()File "extract_bag_images.py", line 15, in extract_imgscv_image = bridge.imgmsg_to_cv2(msg, "bgr8")File "/opt/ros/melodic/lib/python2.7/dist-packages/cv_bridge/core.py", line 163, in imgmsg_to_cv2dtype, n_channels = self.encoding_to_dtype_with_channels(img_msg.encoding)File "/opt/ros/melodic/lib/python2.7/dist-packages/cv_bridge/core.py", line 99, in encoding_to_dtype_with_channelsreturn self.cvtype2_to_dtype_with_channels(self.encoding_to_cvtype2(encoding))File "/opt/ros/melodic/lib/python2.7/dist-packages/cv_bridge/core.py", line 91, in encoding_to_cvtype2from cv_bridge.boost.cv_bridge_boost import getCvType
ImportError: dynamic module does not define module export function (PyInit_cv_bridge_boost)
(base) shl@zhihui-mint:~/extract_rosbag_data$

这篇博客给出了一种这种问题的解决方法

3.3 最终的问题解决方法

最终我解决问题的方式是：

还是用之前使用lz4压缩方式的2020-08-04-16-22-48.bag 文件
但是运行的时候使用python2即可！这是因为python3不支持采用LZ4 压缩的bag包
饶了一大圈，结果就是起点出了问题，FK！

正确的运行命令：

python2 extract_bag_images.py

3.4 解决错误：ImportError: dynamic module does not define module export function (PyInit_cv_bridge_boost)

后面我尝试了没有压缩的bag包文件，依然报错：ImportError: dynamic module does not define module export function (PyInit_cv_bridge_boost) ，这个错误主要是由于cv_bridge 库包对于python3中不兼容！

解决问题参考：

stack overflow
Xavier AGX

4 两种提取雷达数据包中图片的方式

4.1 使用roslaunch提取雷达数据包中的图片

建立export.launch文件, 文件内容如下:

<launch><node pkg="rosbag" type="play" name="rosbag" args="-d 2 /home/jhc/2020-08-04-16-22-48.bag"/><node name="extract" pkg="image_view" type="extract_images" respawn="false" output="screen" cwd="ROS_HOME"><remap from="image" to="/ns1/usb_cam/image_raw"/></node></launch>

其中：

/home/jhc/2020-08-04-16-22-48.bag：是要解析的.bag文件的路径
/ns1/usb_cam/image_raw：是.bag文件中图片所在的位置

下面是提取图片的步骤
1、打开终端运行

roscore

2、再新建一个终端，使用roslaunch运行刚刚新建的export.launch文件

roslaunch export.launch

jhc@jhc-Default-string:~$ roslaunch export.launch
... logging to /home/jhc/.ros/log/7cd4fadc-0eb8-11eb-a4b8-0002a000179a/roslaunch-jhc-Default-string-8501.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.started roslaunch server http://jhc-Default-string:40787/SUMMARY
========PARAMETERS* /rosdistro: kinetic* /rosversion: 1.12.16NODES/extract (image_view/extract_images)rosbag (rosbag/play)ROS_MASTER_URI=http://localhost:11311process[rosbag-1]: started with pid [8519]
process[extract-2]: started with pid [8520]
[ INFO] [1602760999.375392392]: Initialized sec per frame to 0.100000
[ INFO] [1602761001.578548030]: Saved image frame0000.jpg
[ INFO] [1602761001.768274749]: Saved image frame0001.jpg
[ INFO] [1602761001.975395623]: Saved image frame0002.jpg
[ INFO] [1602761002.164784906]: Saved image frame0003.jpg
[ INFO] [1602761002.265436061]: Saved image frame0004.jpg
[ INFO] [1602761002.373386619]: Saved image frame0005.jpg
[ INFO] [1602761002.565808322]: Saved image frame0006.jpg
[ INFO] [1602761002.669046955]: Saved image frame0007.jpg......
[ INFO] [1602755793.105539345]: Saved image frame2021.jpg
[ INFO] [1602755793.213051297]: Saved image frame2022.jpg
[ INFO] [1602755793.411856603]: Saved image frame2023.jpg
[ INFO] [1602755793.616882581]: Saved image frame2024.jpg
[ INFO] [1602755793.719490581]: Saved image frame2025.jpg
[ INFO] [1602755793.918996288]: Saved image frame2026.jpg
[rosbag-1] process has finished cleanly
log file: /home/jhc/.ros/log/7cd4fadc-0eb8-11eb-a4b8-0002a000179a/rosbag-1*.log

解析的图片在home下的 .ros目录里，你可以移动到你想存放的目录中！

4.2 使用python库包rogbag、cv_bridge、cv2提取

代码如下：

import rosbag
import cv2
from cv_bridge import CvBridge#bag_file = './extract_images/2020-08-04-16-22-48.bag'
bag_file = './2020-08-04-16-22-48.bag'
bag = rosbag.Bag(bag_file, "r")bridge = CvBridge()
bag_data_imgs = bag.read_messages('/ns1/usb_cam/image_raw')def extract_imgs():i = 1for topic, msg, t in bag_data_imgs:cv_image = bridge.imgmsg_to_cv2(msg, "bgr8")print(type(cv_image))  # <type 'numpy.ndarray'>#cv2.imshow("Image window", cv_image)#cv2.waitKey(3)cv2.imwrite("./extract_images/%05d.png" % i, cv_image)i+=1if __name__ == '__main__':extract_imgs()

4.3 两种提取雷达数据包中图片的结果对比

提取方式	共提取帧数量	提取视频帧的大小	合成视频时长	合成视频帧率	合成视频分辨率
直接使用roslaunch	1966	1280x720	00:01:18	25	1280x720
使用python库包cv_bridge	3125	1280x720	00:02:05	25	1280x720

注意：

图片序列合成视频：ffmpeg -f image2 -i %05d.png composition.mp4

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解决错误：No module named ‘Cryptodome‘ 和错误rosbag.bag.ROSBagException: unsupported compression type: lz4