fontsdf

Signed Distance Field (SDF) textures can be used to render text or other vector art more flexibly[1], with higher quality while using less video memory (for the texture).

This no_std library renders SDF:s directly and not by downscaling a higher resolution rasters.

[1] For example:

• It is possible to use single a 64px glyph to render both 14px and 200px glyphs.
• It is easy to add glow, outlines and such.

Comparisons:

NOTE: Use fontdue for simple glyphs instead. It is a lot faster.

Task	SDF	regular
High resolution glyphs	✓	✓
Medium resolution glyphs	✓	✓
Low resolution glyphs		✓
Stretched or squished glyphs	✓
Shadows borders and effects	✓
GUI:s		✓
3D game worlds	✓

• ✅ means it is good at

Example usage with image:

let font = fontsdf::Font::from_bytes(..).unwrap();

let (metrics, sdf) = font.rasterize('x', 64.0, true);
image::GrayImage::from_raw(metrics.width as _, metrics.height as _, sdf)
	.unwrap()
	.save("sdf_x.png")
	.unwrap();

Example output:

Normal

SDF

Example results:

Normal

• 128x156
• 80px font size

SDF

• 128x128
• 48px (+radius) font size (32px input size should be enough for any output size)
• 'free' shadow

TODO:

• dual distance field (https://steamcdn-a.akamaihd.net/apps/valve/2007/SIGGRAPH2007_AlphaTestedMagnification.pdf)