Issue loading saved map when saved under a subdirectory

[nakai-omer]

Bug report

Required Info:

• Operating System:
  • Ubuntu 22.04
• ROS2 Version:
  • Humble
• Version or commit hash:
  • ros-humble-navigation2 1.1.0-2jammy.20220607.182532
• DDS implementation:
  • Fast-RTPS

Steps to reproduce issue

Call the map saver server with a map_url that includes a subdirectory:

ros2 service call /map_saver/save_map nav2_msgs/srv/SaveMap "{map_topic: map, map_url: maps/nakai_world, image_format: pgm, map_mode: trinary, free_thresh: 0.25, occupied_thresh: 0.65}"

Expected behavior

Output yaml file image file will have a relative path to the yaml file, and not to current working directory. Conversely, when loading the map, map_server should not append the yaml file's path to the image path, rather it should append the currect working directory to the image path.

Actual behavior

Image path inside the map's yaml file, is relative to current working directory and not to the yaml file.

image: maps/nakai_world.pgm 
mode: trinary
resolution: 0.05
origin: [-9.39e-05, -0.68, 0]
negate: 0
occupied_thresh: 0.65
free_thresh: 0.25

Additional information

When trying to later load the map using map_server, getting the following error:

[ERROR] [map_io]: Failed to load image file ./maps/maps/nakai_world.pgm for reason: Magick: Unable to open file (./maps/maps/nakai_world.pgm) reported by magick/blob.c:3089 (OpenBlob)

All commands were ran under the same working directory.

[SteveMacenski]

@AlexeyMerzlyakov please add this to your queue.

Output yaml file image file will have a relative path to the yaml file, and not to current working directory.

The actual command is going to be relative to your requested location. Right, if you give a relative location, it'll be relative to where you called it. So assuming when you call SaveMap with a relative path for the yaml of ./my_relative/path, you're saying that the YAML is correct, yes? Its just the image file that is wrong?

Conversely, when loading the map, map_server should not append the yaml file's path to the image path, rather it should append the currect working directory to the image path.

It sounds like the image: maps/nakai_world.pgm needs to just me nakai_world.pgm and the file itself is stored in the relative directory maps. Is that what you're looking for? I agree that that would be sensible.

Please be very particular, when exact commands, directories executed, and output file locations / contents describe your problem so we can reproduce a minimal case and resolve it, where appropriate. Your existing description is a bit too non-specific and vague for me to grasp what you're saying the specific issue is.

[nakai-omer]

First of all, thanks for the quick reply.

Directory structure:

• src
  • maps
    • nakai_world.pgm
    • nakai_world.yaml

Current working directory is src.

Inside of src we run the following command:

ros2 service call /map_saver/save_map nav2_msgs/srv/SaveMap "{map_topic: map, map_url: maps/nakai_world, image_format: pgm, map_mode: trinary, free_thresh: 0.25, occupied_thresh: 0.65}"

Result, files are created as expected under the maps folder in the structure described above.

YAML contains:

image: maps/nakai_world.pgm 
mode: trinary
resolution: 0.05
origin: [-9.39e-05, -0.68, 0]
negate: 0
occupied_thresh: 0.65
free_thresh: 0.25

Next, still under src directory we load a "map_server" node with the following config:

yaml_filename: "maps/nakai_world.yaml"

Result, map_server successfully loads nakai_world.yaml, but fails to load the nakai_world.pgm

[ERROR] [map_io]: Failed to load image file ./maps/maps/nakai_world.pgm for reason: Magick: Unable to open file (./maps/maps/nakai_world.pgm) reported by magick/blob.c:3089 (OpenBlob)

It could be solved in (at least) two ways:

1. Inside the YAML file, map_saver will make the path to the map image relative to the location of the YAML file. In our case ./nakai_world.pgm or just nakai_world.pgm, instead of maps/nakai_world.pgm.
2. map_server will look for the image without prefixing the YAML file's directory. In our case, instead of maps/maps/nakai_world.pgm, it should be just maps/nakai_world.pgm

[SteveMacenski]

Makes sense. I think (1) is the easiest, basically just strip out any relative paths when saving the yaml's image field. If we always save them side-by-side anyway, then there's no reason for any prefix to exist there. That should be a relatively easy fix.

[nakai-omer]

Created a PR #3082