Milky2018/moon_skrifa

A MoonBit library for OpenType font reading and outline drawing.

It provides:

• font metadata access (cmap, names, metrics, variation axes)
• bitmap glyph access (sbix, CBDT/EBDT)
• color glyph paint traversal (COLR)
• outline extraction and drawing (glyf, CFF, CFF2)

Repository: https://github.com/moonbit-community/moon_skrifa

Packages

• Milky2018/moon_skrifa: facade exports for common entry points
• Milky2018/moon_skrifa/core: font metadata, metrics, strings, bitmap/color helpers
• Milky2018/moon_skrifa/outline: outline extraction, pens, and SVG path helpers

Install

Add dependency imports in moon.pkg:

import {
  "moonbitlang/core/prelude",
  "moonbitlang/core/bytes",
  "Milky2018/moon_skrifa" @moon_skrifa,
  "Milky2018/moon_skrifa/outline" @moon_skrifa_outline,
}

Quick Start

let font = @moon_skrifa.FontRef::new(font_bytes).unwrap()
let outlines = @moon_skrifa_outline.OutlineGlyphCollection::from_font(font)

let cmap = font.charmap().unwrap()
let gid = cmap.glyph_id(0x41).unwrap() // 'A'

let settings =
  @moon_skrifa_outline.DrawSettings::unhinted(
    @moon_skrifa.Size::new(16.0),
    @moon_skrifa.LocationRef::default(),
  )

let svg_path = outlines.svg_path(gid, settings).unwrap()

Core API Guide

Variation Axes and Locations

Build normalized locations from user-space axis values:

let axes = font.axes()
let settings : Array[@moon_skrifa.VariationSetting] = Array::from_fixed_array([
  @moon_skrifa.Setting::new(@moon_skrifa.Tag::from_str("wght").unwrap(), 700.0),
])
let loc = axes.location(settings.op_as_view()).as_ref()

Character Mapping

let cmap = font.charmap().unwrap()
let gid = cmap.glyph_id(0x4F60).unwrap() // example codepoint

Localized Name Strings

let family = font.localized_strings(@moon_skrifa.STRING_ID_FAMILY_NAME)
match family.english_or_first() {
  None => ()
  Some(s) => {
    let lang = s.language() // Option[String]
    let value = s.to_string()
    lang |> ignore
    value |> ignore
  }
}

Metrics

let fm = font.metrics(
  @moon_skrifa.Size::new(16.0),
  @moon_skrifa.LocationRef::default(),
)
let gm = font.glyph_metrics(
  @moon_skrifa.Size::unscaled(),
  @moon_skrifa.LocationRef::default(),
)

let aw = gm.advance_width(gid)
let lsb = gm.left_side_bearing(gid)
let bounds = gm.bounds(gid)

fm |> ignore
aw |> ignore
lsb |> ignore
bounds |> ignore

Bitmap Glyphs

let strikes = font.bitmap_strikes()
for i in 0..<strikes.len() {
  let strike = strikes.get(i).unwrap()
  let bmp = strike.get(gid)
  bmp |> ignore
}

Color Paint Traversal (COLR)

Implement ColorPainter, then call:

let loc = @moon_skrifa.LocationRef::default()
try! font.paint_colr_v1_at(gid, loc, painter) |> ignore

Outline API Guide

Unhinted Draw

let settings =
  @moon_skrifa_outline.DrawSettings::unhinted(
    @moon_skrifa.Size::new(16.0),
    @moon_skrifa.LocationRef::default(),
  )
let path = outlines.path(gid, settings)
path |> ignore

Hinted Draw

let hinter =
  @moon_skrifa_outline.HintingInstance::new(
    outlines,
    @moon_skrifa.Size::new(16.0),
    @moon_skrifa.LocationRef::default(),
    @moon_skrifa_outline.HintingOptions::default(),
  ).unwrap()

let settings = @moon_skrifa_outline.DrawSettings::hinted(hinter, false)
let svg = outlines.svg_path(gid, settings)
svg |> ignore

Path Styles

DrawSettings supports:

• PathStyle::FreeType
• PathStyle::HarfBuzz

Set with:

let settings =
  @moon_skrifa_outline.DrawSettings::unhinted(
    @moon_skrifa.Size::new(16.0),
    @moon_skrifa.LocationRef::default(),
  ).with_path_style(@moon_skrifa_outline.PathStyle::HarfBuzz)
settings |> ignore

Development

• moon check
• moon test
• moon fmt
• moon info