Analytic rasterization
Grayscale and RGB/BGR LCD coverage with gamma, darkening, and subpixel positioning.
Font outlines in. Pixels out. Pure Ruby.
Read TrueType, OpenType, and TTC files, extract their outlines, and render antialiased grayscale, LCD, or color glyph bitmaps— without native extensions.
gem install alhena
- Width
- 23 px
- Height
- 36 px
- Channels
- R8
One path from font table to bitmap.
- 1Parse tables
- 2Resolve glyph
- 3Build outline
- 4Rasterize coverage
The rendering layer Ruby was missing.
Alhena keeps the path from raw font bytes to immutable bitmap coverage inside one dependency-free Ruby library.
Variable fonts
Inspect axes and render persistent instances across fvar, gvar, avar, HVAR, and VVAR data.
Color glyphs
Render COLR/CPAL layers and embedded sbix or CBDT/CBLC bitmap strikes.
Bounded by design
Lazy table parsing, checked reads, immutable output, and entry- or byte-bounded LRU caching.
A glyph bitmap in six lines.
The API exposes the useful result without hiding outlines, metrics, or raw table data.
require "alhena"
font = Alhena::Font.open("NotoSans-Regular.ttf")
glyph = font.glyph_id("A")
bitmap = font.rasterize(glyph, size: 24)
puts bitmap.to_asciiBroad font support, explicit limits.
Supported paths are documented precisely. Unsupported structures fail with typed errors.
- Containers
- TrueType, OpenType CFF1/CFF2, TTC
- Unicode maps
- cmap 0, 4, 6, 12, 13, 14
- Variation
- fvar, gvar, avar v1, HVAR, VVAR
- Color
- COLR/CPAL v0, sbix PNG, CBDT/CBLC
Shaping, hinting, kerning, and system font discovery stay outside Alhena’s scope. Pair it with the specialist tool your application needs.
Measured, not promised.
Median local measurements on Ruby 4.0 with YJIT on arm64-darwin24.
- Open Noto Sans
- 64.73 µs
- Rasterize A at 14 px
- 40.11 µs
- Cached glyph hit
- 0.48 µs
- Prewarm 95 ASCII glyphs
- 4.79 ms
Render your first glyph.
gem install alhena