Internationalization ​

The headless browser has access to whatever fonts the host OS / container provides. The Docker image bundles Noto Sans CJK, which covers Japanese, Chinese, and Korean without tofu.

Japanese labels ​

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Why it works ​

• In Docker: the Dockerfile installs fonts-noto-cjk. Chromium picks it up automatically as the fallback for CJK glyphs.
• On your host (without Docker): whatever your OS uses. On macOS and recent Windows, CJK just works. On fresh Linux minimal installs, you may need to apt install fonts-noto-cjk or similar.

Verifying a non-default locale ​

Quickest smoke test:

# JA
echo '{"type":"bar","data":{"labels":["東京"],"datasets":[{"data":[1]}]}}' \
  | chartjs2img render -o /tmp/ja.png

# ZH
echo '{"type":"bar","data":{"labels":["北京","上海"],"datasets":[{"data":[1,2]}]}}' \
  | chartjs2img render -o /tmp/zh.png

# KO
echo '{"type":"bar","data":{"labels":["서울","부산"],"datasets":[{"data":[1,2]}]}}' \
  | chartjs2img render -o /tmp/ko.png

If any of those render as boxes, check font install on the host (or use the Docker image).

Right-to-left scripts ​

RTL (Arabic, Hebrew) also render correctly — Chart.js + Chromium handle the text layout natively. Punctuation and bidi isolates behave as expected. We don't ship an RTL-specific font pack; the glyph coverage of Noto Sans gets you there on most systems.

Forcing a specific font ​

Chart.js options.font.family cascades down to every text element. Whatever you set needs to be installed on the server. chartjs2img doesn't preload custom fonts — you own that layer if the default stack doesn't cover your content.