Yeah, save your map as a png file, then open it in GIMP.
There are several options to transform your picture, black and white being one. I use a "sepia" or parchment transform, it comes out looking all light tan and black as if it was written on parchment or leather.
If you're using CC3 or CC3+, you can also add an RGB Matrix Process effect to the whole drawing. Edit the effect and select the "gray" or "sepia" predefine. When you click OK, your drawing will be just grays or sepia toned. If you want literal black and white (no grays), then you would probably do best to use one of the pure black and white symbol sets.
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There are several options to transform your picture, black and white being one. I use a "sepia" or parchment transform, it comes out looking all light tan and black as if it was written on parchment or leather.