ocrd-segment 0.2.2
Page segmentation and segmentation evaluation in the OCR-D framework
License: Apache License 2.0
Requires Python: >=3.8
Keywords: ocr, ocr-d

# ocrd_segment

This repository aims to provide a number of [OCR-D](https://ocr-d.de) [compliant](https://ocr-d.de/en/spec) [processors](https://ocr-d.de/en/spec/cli) for layout analysis and evaluation.

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## Installation

In your [Python virtual environment](https://packaging.python.org/guides/installing-using-pip-and-virtual-environments/), run:

    pip install ocrd_segment

## Usage

Contains processors for various tasks:

- exporting segment images (including results from preprocessing like cropping/masking, deskewing, dewarping or binarization) along with polygon coordinates and metadata:
  - [ocrd-segment-extract-pages](ocrd_segment/extract_pages.py) (for pages, also exports [MS-COCO](https://cocodataset.org/) format and pageview plots)
  - [ocrd-segment-extract-regions](ocrd_segment/extract_regions.py) (for regions, so exports [MS-COCO](https://cocodataset.org/) format))
  - [ocrd-segment-extract-lines](ocrd_segment/extract_lines.py) (for lines, also exports text and .xlsx)
  - [ocrd-segment-extract-words](ocrd_segment/extract_words.py) (for words, also exports text)
  - [ocrd-segment-extract-glyphs](ocrd_segment/extract_glyphs.py) (for glyphs, also exports text)
- importing layout segmentations from other formats:
  - [ocrd-segment-from-masks](ocrd_segment/import_image_segmentation.py) (for mask/label images, i.e. semantic segmentation)
  - [ocrd-segment-from-coco](ocrd_segment/import_coco_segmentation.py) (for [MS-COCO](https://cocodataset.org/) annotation)
- post-processing or repairing layout segmentations:
  - [ocrd-segment-repair](ocrd_segment/repair.py) (validity and consistency of all coordinates; also, for regions, reduce overlaps/redundancy between neighbours, and/or simplify polygons, and/or shrink to the alpha shape of foreground contours)
  - [ocrd-segment-project](ocrd_segment/project.py) (remake segment coordinates into the concave hull / alpha shape of their constituents)
  - [ocrd-segment-replace-original](ocrd_segment/replace_original.py) (rebase all segments on cropped+deskewed border frame as new full page)
  - [ocrd-segment-replace-page](ocrd_segment/replace_page.py) (2 input fileGrps; overwrite segmentation below page of first fileGrp by all segments of second fileGrp, rebasing all coordinates; "inverse" of `replace-original`)
  - [ocrd-segment-replace-text](ocrd_segment/replace_text.py) (insert text below page from single-segment text files; "inverse" of `extract-*`)
- comparing different layout segmentations:
  - [ocrd-segment-evaluate](ocrd_segment/evaluate.py) :construction: (2 input fileGrps; align, compare and evaluate page segmentations; early stage)
  - [page-segment-evaluate](ocrd_segment/evaluate.py) (same with standalone CLI)
- pattern-based segmentation (input file groups N=1, based on a PAGE template, e.g. from Aletheia, and some XSLT or Python to apply it to the input file group)
  - `ocrd-segment-via-template` :construction: (unpublished)
- data-driven segmentation (input file groups N=1, based on a statistical model, e.g. Neural Network)  
  - `ocrd-segment-via-model` :construction: (unpublished)

For detailed behaviour, see `--help` on each processor CLI.
For detailed description on input/output and parameters, see [ocrd-tool.json](ocrd_segment/ocrd-tool.json) or `--dump-json` on each processor CLI.

## Development

### Prerequisities

Requires `libgeos-dev` library for building `shapely` binary requirement, see [Shapely Installation from source](https://shapely.readthedocs.io/en/stable/installation.html#installation-from-source-with-custom-geos-libary). Please ensure it's available before trying to install local requirements.

## Testing

None yet.