OCR-D/Lobby

We have just released a new version of ocrd_all with major changes in ocrd_tesserocr and ocrd_cis. In this context, we have also revised (OCR-D/ocrd-website#189) the workflow guide on OCR-D's homepage.

Notably, ocrd_tesserocr has been refactored so that all the segmentation processors delegate to ocrd-tesserocr-recognize and behavior is controlled by the parameters segmentation_level, textequiv_level and model. See the workflow guide's section on region segmentation, https://github.com/OCR-D/tesserocr README and the --help output for details.

This allows you to use Tesseract for region and line segmentation (and even deskewing and recognition) in one step, reducing the problem of overlap and loss of precision between API calls when running in multiple separate workflow steps. For single-step multi-level segmentation there is a new shorthand processor ocrd-tesserocr-segment, but the old single-level processors still exist, too.

To better address the problem of overlap (even in single-level segmentation), the new option shrink_polygons=true allows annotating tight hull polygons for all new segments instead of coarse bounding boxes.

ocrd-tesserocr-recognize now also exposes all internal Tesseract variables in a new tesseract_parameters dict.

There is one backwards incompatibility, though: overwrite_words has been renamed and generalized to overwrite_segments.

Another new processor is ocrd-tesserocr-fontshape, that uses tesseract's pre-LSTM models to detect font styles like italic, bold and more - very useful for works where font style conveys semantics, like dictionaries or thesauri.

While ocrd-typegroups-classifier, a processor that can predict a wide variety of (historical) fonts/types including confidence for a page, has been part of ocrd_all for a long time, it is now also documented in the workflow guide.

The second major update is cisocrgroup/ocrd_cis#77, which brings not only lots of fixes for robustness and speed, but also improves the incremental behaviour of segmentation, makes clipping and resegmentation optimise globally instead of locally, and allows a page level resegmentation (reassigning conflicting text lines between overlapping regions).

Further, ocrd-segment-repair now finally tries to fix PAGE invalidities and inconsistencies automatically.

Last but not least, we have revised the workflow recommendations, which now offer a single-processor workflow as a benchmark test for more involved workflows, and contain improved/simplified configurations for the "best" and "fast" workflows.