Is there a way to turn outline font into monoline?

Eimantas Paškonis

Maybe there is some sort of Python script for Glyphs that averages out shapes and turns normal outlines into single open lines?

Theunis de Jong

That naive algorithm would fail at "0".

Hrant Հրանդ Փափազեան Papazian

@Eimantas Paškonis Your title versus your post is confusing. Do you mean deriving a "skeleton" from the body?

Paul Miller

I think what he means is turning a standard font format into a monoline format of the sort used by CNC Engraving Machines.

In this format open contours are the norm, i.e. contours which do not (necessarily) return to their starting point.

James Puckett

If you want to do CNC/engraving fonts you’re going to have a tough time. There are some old threads about this in the Glyphs forum: 
https://forum.glyphsapp.com/t/single-stroke-font-like-font-for-cnc-engraving/660/4
https://forum.glyphsapp.com/t/help-with-glyphs-path-definition-for-single-stroke-typeface-for-cnc-engraving-use/3390

Thomas Phinney

Important to note: Many things that consume fonts will choose to pretend that the shapes are closed, even when they are not. So in those environments, they [the deliberately unclosed single-stroke glyphs] will look like bizarre/bad shapes that are not useful to anybody. At a practical level this can be almost indistinguishable from the thing you might be worried about, the font editor closing the shapes for you.

Above I am quoting from what I wrote about how to do this in FontLab Studio 5 back in 2015. I have not yet revisited the question for FontLab VI. https://blog.fontlab.com/type-design/how-to-make-stroke-only-fonts-in-fontlab-studio-5/

Paul Miller

I suppose it might be possible to simulate an open contour with a closed contour by having it retrace the same path (or almost the same path) twice thus getting back to its origin then it could be a closed contour and might also be compatible with CNC Engraving machines.

I don't know maybe I'm missing something which makes this approach impractical.

Eimantas Paškonis

Yes, it's for a plotter holding a pen. We currently have a custom scrip font already done for a special occasion but there's a desire to use plotter to "write" using that font. I have zero experience with engraving fonts though, so I'm lost.

Oh, and the font was created with Glyphs, not FL.

Johannes Neumeier

I've only used some low end prototyping machines, so forgive my ignorance. Do all CNC machines actually use movement path based input, or do you even need the actual movement paths? I recall the Roland machine I used accepted even pixel images and would internally calculate its required tracing paths based on the bit you selected via some proprietary software.
Even if you had a path-only font, wouldn't that still be a step removed from actual milling bit movement instructions, plus you'd have a font design that does not scale with physical size or milling bit size?

Thomas Phinney

My experience with customer requests has been that the path-based font I describe above (and in my FontLab blog post) was what they needed, and worked for them.

Dave Rowland

For what it's worth, I've just done a custom CNC font, and the client specifically did not want a single line font - just a thin monoline outline font.

Eimantas Paškonis

So there's this old thread on Glyphs forum that deals with the same question.

Erwin Denissen

Another thread worth mentioning is

Creating a single stroke ttf from ai files

Thomas Phinney

Dave Rowland said:

For what it's worth, I've just done a custom CNC font, and the client specifically did not want a single line font - just a thin monoline outline font.

Interesting, opposite of my experience—but I expect it depends on the device, and that needs may have changed / be changing over time.