Text recognition (OCR)

When a document has no embedded text, Niraqua DjVu can recognize the text on its pages (OCR) so you can search and select it.

Using an iPhone or iPad? See On iPhone and iPad.

When to use it

Use text recognition when search finds nothing or you cannot select any text. That usually means the document is a scan with no text layer.

Run recognition

Choose View > Text Recognition… or press ⌘ ⇧ T.
Pick the language of the document. Recognition handles one language at a time, so choose the one that matches most of the text.
Choose a quality: Fast suits most documents, Accurate takes longer and can read difficult scans better.
Leave Remember for this document turned on to reuse the same language and quality the next time you recognize this document.
Confirm to start. Progress is shown while the pages are processed, along with a rough estimate of how long the run will take.

Languages

Recognition covers 15 languages: English, French, German, Spanish, Italian, Portuguese, Russian, Ukrainian, Polish, Dutch, Turkish, Chinese (Simplified), Chinese (Traditional), Japanese, and Korean.

Fast is available for English, French, German, Spanish, Italian, and Portuguese. For the other nine languages the app recognizes at Accurate quality even if you pick Fast - Fast cannot read them - and the sheet says so when you choose one. That run takes longer, but it produces text rather than nothing.

How it works

Recognition runs entirely on your Mac using Apple’s built-in frameworks. The contents of your pages are never sent over the network.
Results are cached, so a document only needs to be recognized once - reopening it later is instant.
To recognize again with a different language or quality - for example after picking the wrong language - open the sheet again and choose Re-run.
On a re-run, Replace existing text layer decides what happens to the text you already have: turned on, the document’s recognized text is cleared and every page is read again; turned off, only the pages with no text yet are recognized. Changing the language or quality turns it on for you, since the old text came from different settings.

Stop recognition

To stop a run in progress, choose View > Stop Text Recognition, or click Cancel in the Recognizing Text banner above the page. Pages that were already recognized stay searchable.

After recognition

Once recognition finishes, search and text selection work just as they do for documents that already contain text. To bake the recognized text into a shareable file, export to PDF with Enable OCR turned on.