Changelog

[0.2.0] 2026-05-04

NIF binding to Tesseract 5.x (tesseract::TessBaseAPI) built with elixir_make. Refuses to build against Tesseract < 5.0.
All recognition entry points are dirty-CPU-bound NIFs and do not block normal schedulers.
Per-instance ErlNifMutex so accidental concurrent use of a single instance degrades to serialisation rather than undefined behaviour.

Image.OCR.new/1 — build a reusable OCR instance with :locale, :datapath, :psm, :variables options.
Image.OCR.read_text/3 — recognise text into a UTF-8 string.
Image.OCR.recognize/3 — per-word results with confidence and bounding boxes.
Image.OCR.quick_read/2 — one-shot convenience.
Image.OCR.tesseract_version/0 — linked Tesseract library version.

Image.OCR.Input accepts Vix.Vips.Image.t(), file paths, charlists, and in-memory binaries of encoded image data (PNG, JPEG, TIFF, …).
Auto-normalisation of pixel format (cast to 8-bit, RGBA flatten, band reduction) before recognition.

Image.OCR.Pool — NimblePool-backed pool of OCR instances. One TessBaseAPI* per worker for true parallelism. Pool size defaults to System.schedulers_online().

The :locale option on Image.OCR.new/1 accepts ISO 639-1 codes ("en", :fr), BCP-47 region/script tags ("zh-Hans", "sr-Latn"), Tesseract codes verbatim ("frk", "osd"), and +-joined combinations ("en+fr").
"zh" is rejected as ambiguous — callers must use "zh-Hans" or "zh-Hant".
Optional :localize dependency enables full BCP-47 parsing ("en-US", "fr-CA", "zh-Hans-CN", "sr-Latn-RS"). Compile-fenced — Localize is not required.

Image.OCR.Tessdata resolves the trained-data directory in this order: explicit :datapath option → :image_ocr, :tessdata_path config → TESSDATA_PREFIX env → vendored priv/tessdata/.
English (eng) tessdata_fast is vendored so the package is usable out of the box.
Mix tasks: image.ocr.tessdata.{add,update,list,remove} accept the same language identifiers as the runtime API. --variant selects fast (default), best, or legacy.

CI matrix across Elixir 1.17 / 1.18 / 1.19 / 1.20-rc and OTP 26 / 27 / 28. Lint cell runs mix format --check-formatted and mix dialyzer.
Dialyzer configured with plt_add_apps: [:mix, :inets, :ssl, :public_key, :ex_unit].
Demo Livebook at livebooks/demo.livemd.