[ros-users] how to publish JPEG images with compressed_image_transport ?

[Patrick Mihelich]

As far as topics go, on the publisher side you should append "/compressed"
to your intended topic name, e.g. "stereo/left/image_raw/compressed". Then
any node using image_transport can subscribe to the base topic
"stereo/left/image_raw" as long as you set the parameter ~image_transport to
"compressed", for example:

$ rosrun image_view image_view image:=stereo/left/image_raw
_image_transport:=compressed

image_transport was not really designed with this use case in mind, but it
does work.

Patrick

On Tue, Mar 16, 2010 at 8:12 AM, Jeremy Leibs <leibs at willowgarage.com>wrote:

> The axis_camera node in the texas_drivers stack does exactly this.
>
>
> https://code.ros.org/trac/wg-ros-pkg/browser/stacks/texas_drivers/trunk/axis_camera/axis.py
>
> The relevant snippets (python code, but C++ would be almost identical):
>
> Create the appropriate publishers ("compressed" and "camera_info"
>
>    self.pub = rospy.Publisher("axis_camera/compressed", CompressedImage,
> self)
>    self.caminfo_pub = rospy.Publisher("axis_camera/camera_info",
> CameraInfo, self)
>
>
>
> Populate the appropriate messages and publish:
>
>      img = fp.read(content_length)
>
>      msg = CompressedImage()
>      msg.header.stamp = rospy.Time.now()
>      msg.format = "jpeg"
>      msg.data = img
>
>      self.axis.pub.publish(msg)
>
>      cimsg = CameraInfo()
>      cimsg.header.stamp = msg.header.stamp
>      cimsg.width = self.width
>      cimsg.height = self.height
>
>      self.axis.caminfo_pub.publish(cimsg)
>
>
> On Tue, Mar 16, 2010 at 7:10 AM, Rene Ladan <r.c.ladan at gmail.com> wrote:
> > Hi,
> >
> > I'm writing a node to publish images from the Surveyor stereo camera
> > (see http://www.surveyor.com/stereo/ ).
> > The camera publishes the images in JPEG format.  The logical thing
> > would be to somehow feed them to the
> > compressed_image_format node (after setting up a handmade header?) to
> > publish them.  Is there any example
> > code which does this?
> >
> > Also, if I understand correctly, the subscriber can just subscribe to
> > the normal image_transport topic, but needs
> > to have extra code to decompress compressed images before using them?
> >
> > Thanks,
> > Rene
> > --
> > http://www.rene-ladan.nl/
> >
> > GPG fingerprint = E738 5471 D185 7013 0EE0  4FC8 3C1D 6F83 12E1 84F6
> > (subkeys.pgp.net)
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