Bayer support

[Lashhev]

Does the compressed image plugin support bayer image format?

[andrei-ng]

~No, but recently~ there is a PR related to this: https://github.com/ros-perception/image_transport_plugins/pull/98

@Lashhev, I am correcting my previous answer as after an experiment I would say it is supported but not documented.

I perfomed the following experiment with ROS Noetic:

• recorded in a rosbag a compressed topic where the uncompressed raw image is in Bayer format The recording has only a single topic recorded of type

  types:       sensor_msgs/CompressedImage [8f7a12909da2c9d3332d540a0977563f]
  topics:      /pylon_camera_node/image_raw/compressed   125 msgs    : sensor_msgs/CompressedImage

  By echoing the topic, the header states the original image was in bayer format

  rostopic echo /pylon_camera_node/image_raw/compressed
  header: 
  seq: 77
  stamp: 
  secs: 1692615289
  nsecs: 610064228
  frame_id: "pylon_camera"
  format: "bayer_rggb8; jpeg compressed "
  .....
  .....
  [topic values]
  ...
  ...

• I replayed the rosbag and launched an image view node

  rosrun image_view image_view image:=/pylon_camera_node/image_raw/compressed

  the image_view node complains with the following output

  [image_transport] It looks like you are trying to subscribe directly to a transport-specific image topic '/pylon_camera_node/image_raw/compressed', in which case you will likely get a connection error. Try subscribing to the base topic '/pylon_camera_node/image_raw' instead with parameter ~image_transport set to 'compressed' (on the command line, _image_transport:=compressed). See http://ros.org/wiki/image_transport for details.

  By adding the argument as shown in the hint of the warning,

  rosrun image_view image_view image:=/pylon_camera_node/image_raw _image_transport:=compressed

  I get back a color image with the header:

  rostopic echo /image_view/output
  header: 
  seq: 0
  stamp: 
  secs: 1692615291
  nsecs: 312088400
  frame_id: "pylon_camera"
  height: 1200
  width: 1600
  encoding: "bgr8"
  is_bigendian: 0
  step: 4800

  One would have to study the code for the publisher and subscriber in the noetic-devel here and here to check what if/else branches are taken.

If anyone has other experience or knowledge about this, please share, IMO it seems that compression and uncompression is working for Bayer formats as well but it is not documented.