digital-eval 1.5.1

Evaluate Mass Digitalization Data

digital eval

Python3 Tool to report evaluation outcomes from mass digitalization workflows.

Features

• match automatically groundtruth (i.e. reference data) and candidates by filename
• use geometric information to evaluate only specific frame (i.e. specific column or region from large page) of candidates (requires ALTO or PAGE format)
• aggregate evaluation outcome on domain range (with multiple subdomains)
• choose from textual metrics based on characters or words plus common Information Retrieval
• choose between accuracy / error rate and different UTF-8 Python norms
• formats: ALTO, PAGE or plain text for both groundtruth and candidates
• speedup with parallel execution
• additional OCR util:
  • filter custom areas of single OCR files

Installation

pip install digital-eval

Usage

Metrics

Calculate similarity (acc) or difference (err) ratios between single reference/groundtruth and test/candidate item.

Edit-Distance based

Character-based text string minus whitechars (Cs, Characters) or Letter-based (Ls, Letters) minus whites, punctuation and digits. Word/Token-based edit-distance of single tokens identified by whitespaces.

Set based

Calculate union of sets of tokens/words (BoW, BagOfWords). Operate on sets of tokens/words with respect to language specific stopwords using nltk -framework for:

• Precision (IRPre, Pre, Precision): How many tokens from candidate are in groundtruth reference?
• Recall (IRRec, Rec, Recall): How many tokens from groundtruth reference should candidate include?
• F-Measure (IRFMeasure, FM): weighted ratio Precision / Recall

UTF-8 Normalisations

Use standard Python Implementation of UTF-8 normalizations; default: NFKD.

Statistics

Statistics calculated via numpy include arithmetic mean, median and outlier detection with interquartile range and are based on the specific groundtruth/reference (ref) for each metric, i.e. char, letters or tokens.

Evaluate treelike structures

To evaluate OCR-candidate-data batch-like versus existing Groundtruth, please make sure that your structures fit this way:

groundtruth root/
├── <domain>/ 
│    └── <subdomain>/
│         └── <page-01>.gt.xml
candidate root/
├── <domain>/ 
│    └── <subdomain>/
│         └── <page-01>.xml

Now call via:

digital-eval <path-candidate-root>/domain/ -ref <path-groundtruth>/domain/

for an aggregated overview on stdout. Feel free to increase verbosity via -v (or even -vv) to get detailed information about each single data set which was evaluated.

Structured OCR is considered to contain valid geometrical and textual data on word level, even though for recent PAGE also line level is possible.

Data problems

Inconsistent OCR Groundtruth with empty texts (ALTO String elements missing CONTENT or PAGE without TextEquiv) or invalid geometrical coordinates (less than 3 points or even empty) will lead to evaluation errors if geometry must be respected.

Additional OCR Utils

Filter Area

You can filter a custom area of a page of an OCR file by providing the points of an arbitrary shape. The format of the -p, --points argument is <pt_1_x>,<pt_1_y> <pt_2_x>,<pt_2_y> <pt_3_x>,<pt_3_y> ... <pt_n_x>,<pt_n_y> . For simple rectangular areas this can be expressed also with two points, with first point as top left and second point as bottom right: <pt_top_left_x>,<pt_top_left_y> <pt_bottom_right_x>,<pt_bottom_right_y>.

The following example filters a rectangular area of 600x400 pixels of a page, which is described by an input ALTO file and saves the result to an output ALTO file

ocr-util frame -i page_1.alto.xml -p "0,0 600,0 600,400 0,400" -o page_1_area.alto.xml

Short version with top left and bottom right:

ocr-util frame -i page_1.alto.xml -p "0,0 600,400" -o page_1_area.alto.xml

Development

Plattform: Intel(R) Core(TM) i5-6500 CPU@3.20GHz, 16GB RAM, Ubuntu 20.04 LTS, Python 3.8.

# clone local
git clone <repository-url> <local-dir>
cd <local-dir>

# enable virtual python environment (linux)
# and install libraries
python3 -m venv venv
. venv/bin/activate
python -m pip install -U pip
python -m pip install -r requirements.txt

# install
pip install .

# optional:
# install additional development dependencies
pip install -r tests/test_requirements.txt
pytest -v

# run
digital-eval --help

Contribute

Contributions, suggestions and proposals welcome!

Licence

Under terms of the MIT license.

NOTE: This software depends on other packages that may be licensed under different open source licenses.