[ros2] image_view only subscribe to raw

[ahcorde]

I'm testing this repository in particular image_view and I found several issues:

I'm publishing images using this command

ros2 run image_transport_tutorials my_publisher img.jpeg

then I try to subscribe to "raw" image using:

ros2 run image_view image_view image:=/camera/image

Up to this point all work fine, but the issues start when I try to use a different image transport plugin

ros2 run image_view image_view compressed image:=/camera/image compressed
[INFO] [1688051408.660552694] [image_view_node]: Using transport "raw"

But I always see this trace : Using transport "raw". This is happening because the NodeOptions is resetting the parameters no matter what you define in the cmd.

I tried

ros2 run image_view image_view image:=/camera/image image_transport:=compresse
ros2 run image_view image_view image:=/camera/image _image_transport:=compresse

But I'm getting the same result, the solution should be something like this. Parse the arguments.

Remapping

Then the second problem that I'm facing is the remapping, when I use the "raw" plugin I'm able to remap the topic from "image" to the one that I want, But If I hardcoded the code to use "compressed" images, the topic is not remapped. I checked this addiing some traces.

are these know issues? or am I doing something wrong ?

Happy to open PRs and find a solution.

[ahcorde]

FYI @JWhitleyWork

[ahcorde]

Probably I know why the second remapping is not happening, when the code susbcribes to the topic it uses getTopicToSubscribe(base_topic), which in this case should be image/compressed and the cmd uses image:= the topics are different. should we use a parameter to define the topic name ? but for this we should fix the first issue.

[ahcorde]

Thinking a little bit more about the second issue, using this remapping is fixed, maybe we should document this better:

ros2 run image_view image_view compressed "/image/compressed:=/camera/image/compressed"

[ahcorde]

I created this PR #825

[vidalperezbohoyo]

I have the same problem:
ros2 run image_view image_view compressed --ros-args --remap image:=/image_compressed

Only using transport raw...

In Ros2 Humble.

[mikeferguson]

So is it possible you're just using the wrong command line? If I do the following:

ros2 run image_view image_view --ros-args --remap image:=/camera/image -p image_transport:=compressed

Which is what is shown in the image_transport_tutorials README, then things work (even using what is in rolling debs right now):

ros2 run image_view image_view --ros-args --remap image:=/camera/image -p image_transport:=compressed
[INFO] [1705521253.837407238] [image_view_node]: Using transport "compressed"

I think this is because without the "-p" newer ROS 2 versions are interpreting this as a remap rather than a parameter

[mikeferguson]

Ok - I might have spoken too soon - I get the "compressed" message (so parameter is going through) but the remap doesn't actually work.. so then:

• "only subscribes to raw" is not actually bug - it works if you use the -p in --ros-args
• "subscribes to the wrong topic" is still an issue - but appears to be an issue with image_transport - there's nothing we can do here from what i see - the workaround is to fully specify the remapped topics (see my next post)

Also, if I update the image_transport_tutorials my_subscriber to use transport hints and switch to compressed, it also does the remappings incorrectly - further confirming the bug is in image_transport

[mikeferguson]

There is definitely something funky going on with the remapping - this fully works against current rolling debs:

ros2 run image_view image_view --ros-args --remap image/compressed:=/camera/image/compressed -p image_transport:=compressed

[mikeferguson]

Based on these comments - I opened #850 to at least correct the help string for image_view to the proper format

[mikeferguson]

I believe that #851 is the correct approach to fix the remap issues - still need to apply that to this particular node

[mikeferguson]

#851 fixes the remapping (in rolling, which means jazzy and beyond - as noted in the PR, this would break anyone who has been manually fixing the remapping issue, so I don't think we should release it into Iron or earlier)

For the image_transport selection - it appears our real issue is lack of documentation - I've specifically called out this image_transport part in my documentation ticket: #848