I cannot figure out what is the exact format of the sensor_msg Image() file. When I issue the command:
rostopic echo /camera/image_raw
I get a massive output consisting of thousands of numbers in an array. However, when I look up the documentation, there is supposed to be a heading, height, width, etc and the actual data. I have never been able to find the header or any other parameter from the output. I also cannot figure out just how large the file is. This makes it difficult to manipulate and transport the data. Can someone please help me out?
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Comment by gvdhoorn on 2021-08-24:
rostopic --help output may offer some guidance here:
--nostr exclude string fields
--noarr exclude arrays
if you add
--noarr to your
rostopic echo command, you'll be able to see the header and other non-array fields.
there is supposed to be a heading
probably a typo, but there is a
header field. Not
This makes it difficult to manipulate and transport the data.
A general usability suggestion: if you can accept the OpenCV dependency, try to consume
sensor_msgs/Image messages using image_transport subscribers and convert messages to their OpenCV representation. That will make it much easier to work with them.
Working directly with the serialised form (in the form of
sensor_msgs/Image) might not be the most efficient (from a usability perspective).