Extraction of data from maps created using gmapping or Hector SLAM

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I wanted to know if there is a way to extract useful data like dimensions of the obstacles recorded on the map created using Gmapping or Hector SLAM?

Currently I am using 2D LiDAR to record the data for mapping and am able to get the corresponding png and yaml file for the map.

I know I can do the required task using the measure tool in Rviz, but I am looking for something that provides me more control over the task like an open source code or library, which I can modify to my liking. Even pointers to creating such a library are welcome.