Image format error when reading ROS compressed images

Hi,

I am trying to read ROS compressed images from Matlab using the following commands. I use a real Turtlebot3 robot.

imgSub = rossubscriber('/raspicam_node/image/compressed');
imgMsg = receive(imgSub);
rgbImg = readImage(imgMsg);

The last line gives this error:

Error using robotics.ros.msg.sensor_msgs.CompressedImage/readImage (line 64)

Could not find a semicolon in format character vector jpg. Modify the "format" property of the message object appropriately.

I found that manually changing the ROS message format solves the problem (change from jpg to bgr8; jpeg compressed bgr8).

imgSub = rossubscriber('/raspicam_node/image/compressed');
imgMsg = receive(imgSub);
imgMsg.Format = 'bgr8; jpeg compressed bgr8';
rgbImg = readImage(imgMsg);

Can someone explain why this happens and if it is possible to solve this without hardcoding the format.

Thanks.

[Francesco Ciriello]

Have you tried using the '/raspicam_node/image/compressed' and '/raspicam_node/image/' messages in the Simulink readImage block? I can't seem to get anything but error code 1, i.e. Incorrect image encoding. Check that the incoming message encoding matches the ImageEncoding parameter.

Answer 1

[Cam Salzberger]

Hello Asanka,

Any messages published by the image_transport package should ensure that the Format field is in the form expected by MATLAB. Consider using the image_transport system on the TurtleBot3, if that is possible.

-Cam

[Asanka Perera]

Thanks Cam. I will check it.