CompressedImage with 16bit grayscale png and image_transport

[NikolausDemmel]

I am recording 16bit grayscale images. So far I have been using Image and everything works fine. Now I would like to use CompressedImage with png encoding instead, since that gives me a > 2x compression rate.

Unfortunately, it seems image_transport has trouble decoding 16bit grayscale png, at least with the mode parameter unchanged which is the default. If I change the mode to either gray or color, it seems to work fine.

To test, I play a bag with encoded images with rosbag play, and try to visualize in rviz. Just adding the appropriate image display does not show images (although messages are received), but changing the mode parameter for the image transport subscriber in rviz using rqt_reconfigure, it works fine (images are displayed).

In image_view it is a similar story, but it shows some heavly corrupted image with the default mode, instead of no image at all:

I would expect the default parameter to work as well. Seems like a bug?

Here is an example bag to reproduce: test.bag.zip

I'm on Ubuntu 16.04 with kinetic.

[NikolausDemmel]

Possibly realated: cv_bridge does not properly support conversions for 16bit pngs: ros-perception/vision_opencv#206