64 lines
2.6 KiB
Markdown
64 lines
2.6 KiB
Markdown
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# TinySDF [](https://github.com/mourner/projects) [](https://github.com/mapbox/tiny-sdf/actions/workflows/node.yml)
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TinySDF is a tiny and fast JavaScript library for generating SDF (signed distance field)
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from system fonts on the browser using Canvas 2D and
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[Felzenszwalb/Huttenlocher distance transform](https://cs.brown.edu/~pff/papers/dt-final.pdf).
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This is very useful for [rendering text with WebGL](https://www.mapbox.com/blog/text-signed-distance-fields/).
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## [Demo](http://mapbox.github.io/tiny-sdf)
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## Usage
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Create a TinySDF for drawing glyph SDFs based on font parameters:
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```js
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const tinySdf = new TinySDF({
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fontSize: 24, // Font size in pixels
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fontFamily: 'sans-serif', // CSS font-family
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fontWeight: 'normal', // CSS font-weight
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fontStyle: 'normal', // CSS font-style
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buffer: 3, // Whitespace buffer around a glyph in pixels
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radius: 8, // How many pixels around the glyph shape to use for encoding distance
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cutoff: 0.25 // How much of the radius (relative) is used for the inside part of the glyph
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});
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const glyph = tinySdf.draw('泽'); // draw a single character
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```
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Returns an object with the following properties:
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- `data` is a `Uint8ClampedArray` array of alpha values (0–255) for a `width` x `height` grid.
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- `width`: Width of the returned bitmap.
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- `height`: Height of the returned bitmap.
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- `glyphTop`: Maximum ascent of the glyph from alphabetic baseline.
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- `glyphLeft`: Currently hardwired to 0 (actual glyph differences are encoded in the rasterization).
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- `glyphWidth`: Width of the rasterized portion of the glyph.
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- `glyphHeight` Height of the rasterized portion of the glyph.
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- `glyphAdvance`: Layout advance.
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TinySDF is provided as a ES module, so it's only supported on modern browsers, excluding IE.
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```html
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<script type="module">
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import TinySDF from 'https://cdn.skypack.dev/@mapbox/tiny-sdf';
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...
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</script>
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```
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In Node, you can't use `require` — only `import` in ESM-capable versions (v12.15+):
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```js
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import TinySDF from '@mapbox/tiny-sdf';
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```
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## Development
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```bash
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npm test # run tests
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npm start # start server for the demo page
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```
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## License
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This implementation is licensed under the [BSD 2-Clause license](https://opensource.org/licenses/BSD-2-Clause). It's based directly on the algorithm published in the Felzenszwalb/Huttenlocher paper, and is not a port of the existing C++ implementation provided by the paper's authors.
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