Can you publish only obstacles from a costmap

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I'm wondering if it is possible to publish only the cells (points) that are occupied in a given costmap_2d object using the newer layered costmap approach in Hydro? This was how the nav_msgs/GridCells worked on the <costmap>/obstacles topic of old and it was a useful feature.

I suppose it would not be terribly difficult to write a node that subscribes to the /costmap topic now and converts the occupancy grid into a GridCells message of occupied cells, but I'm just curious if that functionality is built in to the current implementation of costmap_2d or not. Thanks!