Fix a few minor issues in image_helper

[mjeronimo]

• Used ByteIO rather than StringIO is now required for PIL's Image.open
• Remove unused variable, 'alpha'
• Added support for '8UC1' and '32FC1' image types
• Only do bgr2rgb if it's definitely a BGR type

Fixes #60

Signed-off-by: Michael Jeronimo michael.jeronimo@openrobotics.org

[mabelzhang]

Dependent on #67.

Is there an easy way to test this?

If I right-click on an image thumbnail > View > Raw, then I still see some errors that sound related to the fix here. Maybe that can be fixed at the same time?

Traceback (most recent call last):
  File "/home/developer/viper/catkin_ws/install_isolated/lib/python3/dist-packages/rqt_bag/plugins/message_view.py", line 93, in event
    self.message_viewed(bag, msg_data)
  File "/home/developer/viper/catkin_ws/install_isolated/lib/python3/dist-packages/rqt_bag/plugins/raw_view.py", line 73, in message_viewed
    self.message_tree.set_message(msg)
  File "/home/developer/viper/catkin_ws/install_isolated/lib/python3/dist-packages/rqt_bag/plugins/raw_view.py", line 115, in set_message
    self._add_msg_object(None, '', '', msg, msg._type)
  File "/home/developer/viper/catkin_ws/install_isolated/lib/python3/dist-packages/rqt_bag/plugins/raw_view.py", line 239, in _add_msg_object
    self._add_msg_object(item, subpath, subobj_name, subobj, subobj_type)
  File "/home/developer/viper/catkin_ws/install_isolated/lib/python3/dist-packages/rqt_bag/plugins/raw_view.py", line 239, in _add_msg_object
    self._add_msg_object(item, subpath, subobj_name, subobj, subobj_type)
  File "/home/developer/viper/catkin_ws/install_isolated/lib/python3/dist-packages/rqt_bag/plugins/raw_view.py", line 207, in _add_msg_object
    obj_repr = codecs.utf_8_decode(str(obj), 'ignore')[0]
TypeError: a bytes-like object is required, not 'str'

[mjeronimo]

Sure, I found and fixed the sources of the "TypeError: a bytes-like object is required, not 'str'" It was missing a call to decode and is now like the code found in the plot view plugin.

obj_repr = codecs.utf_8_decode(str(obj).encode(), 'ignore')[0]

[mabelzhang]

I believe I still need a way to test this. If I interpret the changes correctly, 8UC1 and 32FC1 were having problems before? And maybe an image that's a RGB type got converted when it shouldn't be? Do you happen to have data at hand that expose these problems, or was this just a "oh this is obviously wrong code" kind of fix?

[mjeronimo]

@mabelzhang These types showed up when running rqt_bag on ROS2 and using a rosbag from realsense. The same camera resulted in different data types with ROS1. FYI, it seems from here: IntelRealSense/realsense-ros#253, that 'mono8' is preferred, but similar images can come in as '8UC1'.

[mabelzhang]

The mono8 and 8UC1 link looks reasonable.
I was able to test the L and BGR change - it does affect Melodic where CompressedImage was showing up blue where it should have been red. In Noetic CompressedImages are currently not shown, so it's not seen.
I did not have 32FC1 data to test those additions, but they look reasonable enough.

[VictorLamoine]

This PR creates a bug. When trying to display thumbnails/images of compressed images (JPEG) the following error is displayed:

Can't convert image: local variable 'pil_mode' referenced before assignment

Reverting this merge request solves the issue. I'm using ROS melodic

[VictorLamoine]

Example bag file (4.1 Mio)

path:        images_compressed.bag
version:     2.0
duration:    2.0s
start:       Sep 22 2020 14:03:24.01 (1600776204.01)
end:         Sep 22 2020 14:03:25.98 (1600776205.98)
size:        4.1 MB
messages:    60
compression: none [6/6 chunks]
types:       sensor_msgs/CompressedImage [8f7a12909da2c9d3332d540a0977563f]
topics:      /nit_gige_1/image/compressed   60 msgs    : sensor_msgs/CompressedImage

[mjeronimo]

@VictorLamoine Ok, thanks. I'll investigate and fix.

[VictorLamoine]

@mjeronimo did you find what was wrong?

[mjeronimo]

Commented over on the issue, #74, thinking you'd see it. Apologies for not notifying you directly on this thread.