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Maniphest T345055

Add kraken OCR engine to Wikimedia OCR
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Description

Wikimedia OCR currently uses the free Tesseract OCR engine (which only supports printed text) and the commercial Google and Transkribus OCR engines.

The free kraken OCR engine supports printed and handwritten text. Like Tesseract, kraken is used in the OCR-D project for OCR of historic prints. It is much slower than Tesseract, but sometimes gets better results and would be the only available non-commercial OCR engine for handwritings.

I suggest to start with my free models for German print and German handwriting (they are not limited to German, but can be used with other languages which use Latin script as well), but there exist many more models, for example for Arabic or Hebrew script.

I already have implemented a prototype and sent a draft pull request for Wikimedia OCR.

Details

Related Changes in GitLab:
TitleReferenceAuthorSource BranchDest Branch
Add Kraken OCR enginetoolforge-repos/ocr!2samwilsonkrakenmain
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Event Timeline

sweil created this task.Aug 28 2023, 8:27 AM
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sweil updated the task description. (Show Details)Aug 28 2023, 8:28 AM
sweil updated the task description. (Show Details)
MusikAnimal removed a project: Community-Tech.Aug 30 2023, 2:08 PM
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Samwilson moved this task from Backlog to Kraken on the Wikimedia OCR board.Sep 15 2023, 5:38 AM
sweil added a comment.Sep 18 2023, 12:41 PM

The current implementation offers 3 different models for the text recognition.
Is there a need for non Latin scripts as well? Which ones? Arabic? Hebrew? Others?

Kraken also supports different models for the segmentation (region and line detection).
The segmentation model should be selectable from the web interface and the API, too.

sweil added a comment.Sep 19 2023, 3:07 PM
In T345055#9174507, @sweil wrote:

Kraken also supports different models for the segmentation (region and line detection).
The segmentation model should be selectable from the web interface and the API, too.

The implementation now supports different segmentation models for kraken, too. Currently either default or ubma_segmentation can be selected.

sweil closed subtask T346413: Install Kraken OCR (and web service) on a new Wikisource VPS as Resolved.Sep 28 2023, 11:37 AM
Agamyasamuel subscribed.May 30 2025, 7:53 PM
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hubaishan added a comment.Aug 30 2025, 8:37 PM

I support this feature since Transkribus does not support RTL (Arabic, Persian, Hebrew) languages.

Restricted Application added a subscriber: alaa. · View Herald TranscriptAug 30 2025, 8:37 PM
Mdktb added a subtask: T403346: Add Arabic model to kraken OCR.Apr 27 2026, 1:10 PM
Mdktb removed a subtask: T403346: Add Arabic model to kraken OCR.Apr 29 2026, 3:24 PM
CodeReviewBot added a project: Patch-For-Review.May 2 2026, 4:08 PM

samwilson opened https://gitlab.wikimedia.org/toolforge-repos/ocr/-/merge_requests/2

Add Kraken OCR engine

sweil added a subtask: T424818: [Cloud VPS alert][wikisource] Puppet failure on kraken-ocr.wikisource.eqiad1.wikimedia.cloud.May 3 2026, 7:48 AM
sweil added a subtask: T403346: Add Arabic model to kraken OCR.
taavi closed subtask T424818: [Cloud VPS alert][wikisource] Puppet failure on kraken-ocr.wikisource.eqiad1.wikimedia.cloud as Resolved.May 4 2026, 9:03 AM
sweil added a comment.EditedMay 4 2026, 8:45 PM

After the upgrade to Debian trixie, the next step is upgrading wikimedia-ocr and kraken. This is currently not possible because the 20 GB disk space is not sufficient, even after removing most log files and lots of Debian packages (including Tesseract OCR). I think that a total capacity of 40 GB would be needed for a full installation with several kraken models.

Update 2026-05-05: Meanwhile I managed to install kraken. More storage would still be needed for a full installation with Tesseract and kraken, especially for more models.

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