FontForge brand fonts: why changeWeight failed and offset outlines worked

Description and use

A Python script using FontForge replaced the built‑in changeWeight with manual outline offset and miter joins, producing heavier yet sharp‑cornered fonts while respecting OFL license rules.

Problem

Existing free fonts needed a slightly heavier version with sharp corners, but built‑in weight change produced poor results.

Outcome

The offset‑outline method produced heavier, sharper fonts with minimal distortion, while the built‑in changeWeight failed.

Workflow

• Install FontForge Python bindings via apt
• Write 82‑line script to open source font, loop glyphs, modify outlines, rename, write .otf/.ttf, render specimen with Pillow
• Attempt v1: use glyph.changeWeight() with 3%/3.4% weight and tighten spacing
• Observe poor output: clogged counters, nicked terminals, letters kissing
• Implement v2: removeOverlap, stroke outline with circular pen, butt caps, miter joins, keep outer band, merge back, removeOverlap again
• Apply small weight (1%/2%) to preserve shape
• Add chamfer cuts to straight‑line corners meeting angle criteria
• Perform housekeeping: correctDirection, addExtrema, round, adjust side bearings
• Rename font properly, strip old name table entries, append license notice
• Ship modified font with full OFL 1.1 license file
• Deploy iC Volt on tech site and newsletter; C1 Cut not yet used

Evidence

FontForge has a built‑in for this, glyph.changeWeight(). One call per glyph, give it a stroke amount, job done.

Source

It just looked rubbish. The heavy Anton one clogged up, the holes in R, G and 8 nearly closed.

Source

What I actually wanted was "the same letter, a bit fatter, corners still sharp".

Source

v2 also uses way less weight: 1% of the em on C1 Cut, 2% on iC Volt.

Source

Both source fonts are under the SIL Open Font License 1.1.

Source