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55 lines
1.9 KiB
55 lines
1.9 KiB
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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