If it's procedural generation of the dungeon what you're interested in, this tutorial might come in handy. Part 3, in particular, shows you how to create a basic dungeon generator that will produce something similar to this tool. Alternatively, I have some code here, made in Processing.
It's a programming environment with an unfortunate name, hehe. It makes googling a pain. It's very easy to draw stuff, you can find it here: https://processing.org/ The dungeon generation algorithm doesn't really require it though, it should possible to follow in whatever language you're using.