Viewing images inside messages

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Not an answer, just curious:

[..] as soon as possible, to reduce desynchronization due to asynchronous exchanges

is there something in your system that makes using header.stamp for this not possible? It is explicitly meant to synchronise msgs.

Synchronizing messages based on a timestamp would be much harder than just receiving pairs that I know by design have been generated together. The images are correlated at the source, I see as wasteful separating them, then doing additional efforts to re-correlate them.

Synchronising subscriptions is built-in into the middleware (see wiki/message_filters - Policy-based Synchronizer. Using separate dataflows allows you to re-use existing msg defs, in this case Images and ..

.. CameraInfo data.

I'm not claiming that what you're doing is wrong btw, just curious.

Subscribing to a field inside a msg is not universally supported. rostopic echo .. can do it. The relay_field command in the topic_tools pkg can also do it. It can then also republish the field to another topic. That would allow you to use image_view to view the extracted image.

The synchro middleware looks cool, especially to sync separated sources, but in my case I think it would be adding unneeded complexity. Plus I'd like to annotate the images with custom fields, so that would make a lot of things to synchronize, just for the sake of having pure Image messages.

I managed to use echo, but am struggling with relay_field. (I saw your question about it on github, thanks for digging !). I think it's not very practical, from the looks of it: you'd have to explicit every single field of the Image you want to produce, it seems (and even that I didn't manage).