Dynamic Shader to Outline Adjacent Textures?

I have very little experience with Shaders in Unity, so I don't know if this is possible. This is kind of a poor question, but I want to be able to tile adjacent textures and outline them as a group. For example:

If I took 8 of these images:

In a 3x3 pattern it would look like the left image, but the shader would make it look like the right image:

Can this be done? The reason I ask is because I was just going to tile a set of them: one with one border, one with two, one with three, etc with the proper rotations. However that gave me seams due to mipmapping which can't be disabled. I also want the whole object to have a collision box.