feat: outline generation for given path

[armano2]

Fixes #89
unblocks nfroidure/svgicons2svgfont#60 nfroidure/svgicons2svgfont#113

this is still an early draft that need a lot of cleanup, i have been working on this for quite some time and optimization and other changes are required, but outline itself is producing now correct results for most path's (~99%)

i'm also not keen on using bezier in here, but in this first draft that was easiest way to verify if this is feasible

this is a revised and improved version of outline generation that i did in nfroidure/svgicons2svgfont#178

Proposed changes

• implement outline generation

Code quality

• I made some tests for my changes

License

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• I read the project license in the LICENSE file
• I agree with publishing under this project license

[armano2]

draft review and some feedback would be appreciated

[NaridaL]

No arcs?

[NaridaL]

I see generateOutlinePath handles that by doing .aToC, but it's not being validated.

[armano2]

yes current implementation supports only lines and beziers, this def should/could be extended but as POC, i didn't bother

[NaridaL]

Often this is implemented as (...) <= tolerance ** 2 to avoid the sqrt. Just an aside.

[NaridaL]

I would suggest writing a custom function which generate a baseline/snapshot in the form of a viewable SVG. Eg a big table with rows = test_shapes and columns = TEST_CONFIGS (or at least a subset). That way anyone can easily verify that the results make sense. Currently I can't really validate the snapshots without additional effort

[armano2]

I have a web demo that just let me input paths to test all functionalities but I will push just a generator than, unless you prefer web version, example is is ticket

[armano2]

i pushed my testing file that you can add in generateOutlinePath, thats a reason why i have been making those functions :)

writeSvg(createOutlineSvg(path, pathData, options, {
  showControlPoints: true,
  showHandleLines: true,
  showSegmentPoints: true,
  showDirectionArrows: false,
  showBounds: true,
}));

if you think its a good idea, i can push instead of that my website, tho i used vite to serve it locally into something like docs or play folder as separate PR

[NaridaL]

draft review and some feedback would be appreciated

Looks good to me, you have comments and tests. Added a couple of comments.

Wrt bezier.js, I'm fine to depend on it. I think you're mainly using it for the bezier/bezier and bezier/line intersections. Been a while, but iirc those are fairly easy to reimplement.

[armano2]

bezier rn is used for

offsetting:

• offset.ts
• this one is surprisingly hardest to re-implement
  • you have to calculate extremas, normals, roots, ...
  • split/simplify beziers to not have weird shapes (reduce)
  • create new points

splitting (slice):

• eg in trimming

intersection:

• this also use projection and bbox (we have implementation for that that could be extracted)
• l to c
• c to c
• l to l - is handled manually

derivative

  let v1 = prevSegment.derivative(1);
  const v1Mag = Math.sqrt(v1.x * v1.x + v1.y * v1.y);

    if (v1Mag < POINT_TOLERANCE) {
      v1 = createVector(
        prevSegment.points[0],
        prevSegment.points[prevSegment.points.length - 1],
      );
    }