Is there a way to turn outline font into monoline?

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


  • That naive algorithm would fail at "0".
  • @Eimantas Paškonis Your title versus your post is confusing. Do you mean deriving a "skeleton" from the body?
  • 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 PuckettJames Puckett Posts: 1,492
    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:
  • 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.
  • 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 PaškonisEimantas Paškonis Posts: 71
    edited February 7
    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.
  • 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?
  • 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.
  • 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 PaškonisEimantas Paškonis Posts: 71
    edited February 8
    So there's this old thread on Glyphs forum that deals with the same question.
  • Another thread worth mentioning is

    Creating a single stroke ttf from ai files

  • Thomas PhinneyThomas Phinney Posts: 920
    edited February 8
    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.
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