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56 lines
1.9 KiB
56 lines
1.9 KiB
2 years ago
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cubic2quad
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==========
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[](https://github.com/fontello/cubic2quad/actions/workflows/ci.yml)
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[](https://www.npmjs.org/package/cubic2quad)
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[](https://coveralls.io/r/fontello/cubic2quad?branch=master)
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> Aproximates cubic Bezier curves with quadratic ones.
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This package was done to create TTF fonts (those support quadratic curves only).
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Generated curves have the same tangents angles at the ends. That's important to
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keep result visually smooth.
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Algorithm
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---------
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Logic is similar to one from [FontForge](https://fontforge.github.io/bezier.html).
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Steps:
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1. Split quadratic curve into _k_ segments (from 2 at start, to 8 max).
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2. Approximate each segment with tangents intersection approach (see
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[picture](http://www.timotheegroleau.com/Flash/articles/cubic_bezier/quadratic_on_cubic_1.gif) in [article](http://www.timotheegroleau.com/Flash/articles/cubic_bezier_in_flash.htm)).
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3. Measure approximation error and increase splits count if needed (and max not reached).
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- set 10 points on each interval & calculate minimal distance to created
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quadratic curve.
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Usage
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-----
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```js
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var cubic2quad = require('cubic2quad');
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// Input: (px1, py1, cx1, cy1, cx2, cy2, px2, py2, precision)
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var quads = cubic2quad(0, 0, 10, 9, 20, 11, 30, 0, 0.1);
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```
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It converts given quadratic curve to a number of quadratic ones. Result is:
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[ P1x, P1y, C1x, C1y, P2x, P2y, C2x, C2y, ..., Cnx, Cny, P{n+1}x, P{n+1}y ]
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where _Pi_ are base points and _Ci_ are control points.
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Authors
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-------
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- Alexander Rodin - [@a-rodin](https://github.com/a-rodin)
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- Vitaly Puzrin - [@puzrin](https://github.com/puzrin)
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License
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-------
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[MIT](https://github.com/fontello/cubic2quad/blob/master/LICENSE)
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