Setting colors in image to act as colliders?
I'm making a ball rolling maze game, like those little surprise bag toys you used to get in the '90s, I've figured out a way of getting a flat image of a maze tilting with a locked Ortho camera, but now I need the walls to act as colliders. The paths are white, the walls are black lines. Is there any way of making all the black pixels in an image act as colliders without having to manually draw a line on every single edge? Not to sound lazy, but I'm planning on making a bunch of these, and doing every one manually will take SO MUCH TIME! And I'm also just learning C# and have no plan for a GUI for my game yet either.
Alternately can anyone tell me how to get a Sketchup model to actually render in Unity? It 'imports it' without much trouble, but it can't do anything with it once it's in the list. If that could work I could make this a 2.5D game with mazes I make in Sketchup, although applying colliders to those might be a chore as well.
Either way, any help is appreciated.
Update: I've figured out a way of generating a 3D maze via the heightmap/terrain system. It means I can't tilt it to use gravity, but I've gotten the ball controller to make a reasonably realistic simulation of how that works. Still would like to actually use a real tilt system for this eventually, but at least I can make a functional game that plays right.