Converts TTF/OTF fonts into .cpfont files the reader loads from the
SD card β including kerning and ligature data extracted from the font.
1. Font files
Fallback font (fills in glyphs the main font lacks)
2. Sizes and coverage
“Everything in the font” costs device RAM. It takes every glyph
present in the file and records one interval per contiguous run — for a Japanese font
that is thousands of intervals instead of a few dozen, and the reader keeps that table in
RAM for as long as the font is loaded. Measured on a Noto Sans JP build: 26,592 bytes
against 390 for the same coverage via Japanese — full, on a device whose
largest free block is often under 32 KB. Prefer the script presets; reach for this only
when you know the font is narrowly subset already.
Custom coverage
Japanese and Chinese fonts with full CJK coverage rasterize ~7,000 glyphs per size and style β
this can take a few minutes. A Chinese book needs an SC or TC cut: the reader's built-in CJK
glyphs are the Japanese set, so everyday characters such as θΏ, θ―΄ or ε are missing without one. Glyphs are rendered by your browser's font engine, so pixel edges can
differ very slightly from the desktop (FreeType) tool; metrics, kerning, and ligatures are
extracted from the font file itself and match exactly.
Install on the device
The download is a zip containing .fonts/FamilyName/FamilyName_<size>.cpfont.
Unzip it at the SD card root (the .fonts folder may be hidden in your file
manager β that's normal), or upload via the reader's Wi-Fi web file transfer. The font then
appears in the reader's font settings.