Dungeon Generator
github.com
github.com
For more complex maps, it might be worth using something like DOT to define the abstract graph, and use any image generator tools to layout the dungeon. As a bonus, it would generate curved hallways to link the rooms.
https://en.wikipedia.org/wiki/DOT_(graph_description_languag...
You seem to have specific requirements for the image to be easily loadable into a Voxel engine, so it may be that this method wouldn't be useful.
I've added a more detailed description how to use the array and its values to the README file.
There is also a pure-JS version which works offline, downloadable from here: http://donjon.bin.sh/apps/