Not all map objects appear

[jhudsy]

I'm trying to create a simple office layout with map2gazebo. However, many of the walls don't appear in the resultant STL file. This seems to be something to do with the way opencv is creating the contours, but I'm struggling to fix it. Attached is my input file (converted from tiff to png).

[jhudsy]

As a follow-up, I guess this is just a weakness of using a specific CV approach, but I'm wondering if there's a better way to approach the transformation.