TinySDF

TinySDF is a tiny and fast JavaScript library for generating SDF (signed distance field) from system fonts on the browser using Canvas 2D and Felzenszwalb/Huttenlocher distance transform. This is very useful for rendering text with WebGL.

Demo

Usage

Create a TinySDF for drawing glyph SDFs based on font parameters:

consttinySdf=newTinySDF({fontSize: 24,// Font size in pixelsfontFamily: 'sans-serif',// CSS font-familyfontWeight: 'normal',// CSS font-weightfontStyle: 'normal',// CSS font-stylebuffer: 3,// Whitespace buffer around a glyph in pixelsradius: 8,// How many pixels around the glyph shape to use for encoding distancecutoff: 0.25// How much of the radius (relative) is used for the inside part of the glyph});constglyph=tinySdf.draw('泽');// draw a single character

Returns an object with the following properties:

• data is a Uint8ClampedArray array of alpha values (0–255) for a width x height grid.
• width: Width of the returned bitmap.
• height: Height of the returned bitmap.
• glyphTop: Maximum ascent of the glyph from alphabetic baseline.
• glyphLeft: Currently hardwired to 0 (actual glyph differences are encoded in the rasterization).
• glyphWidth: Width of the rasterized portion of the glyph.
• glyphHeight Height of the rasterized portion of the glyph.
• glyphAdvance: Layout advance.

TinySDF is provided as a ES module, so it's only supported on modern browsers, excluding IE.

<scripttype="module">importTinySDFfrom'https://cdn.skypack.dev/@mapbox/tiny-sdf';
...
</script>

In Node, you can't use require — only import in ESM-capable versions (v12.15+):

importTinySDFfrom'@mapbox/tiny-sdf';

Development

npm test# run tests
npm start # start server for the demo page

License

This implementation is licensed under the BSD 2-Clause license. 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.