Add a tolerance parameter to 2dbitmap and 1dbitmap

[dimo414]

Since the bits are coincident it can leave non-manifold artifacts in models.

Before:

After:

[dimo414]

@X-Illuminati any interest in this PR?

[X-Illuminati]

@dimo414 ,
I see what you mean, and I had the same problem with the 2dbitmaps when creating the dogtag example. Initial attempts at a 3d-printable STL required a lot of cleanup in meshmixer, as I recall.
What I am seeing now is that I need 0.003 in order to avoid artifacts in the preview window. (Although, I would guess that 0.001 resolves the problem when a full render is performed.)

I had previously added an expansion parameter to the 2dbitmaps to resolve this. However, I never introduced any default expansion into the 1dbitmaps. I think I forgot to go back and make the changes.

Also, it looks like you and I took different approaches to solving the problem.
The "expansion" parameter I added is really a "pull-back" and is therefore misnamed.
Again, this was probably because of my focus on the 3d-printing use-case for the 2d barcodes - not only does it clean up the non-manifold edges, but you generally want to shrink things that are going to fit together as they will expand a bit when printed in plastic.
Example with expansion=.1:

In any case, what you have done makes sense for the 1dbitmaps - I will probably just implement it as a default "expansion" of -0.003, though. (Actually, I will probably change the logic so that expansion makes sense as a positive value instead.)

[X-Illuminati]

Commit 91bcd82 changes the name of the expansion parameter to "pullback" and adds it in as an option to the UPC and Code128 barcodes. The default is -0.003.