eihli / image-table-ocr

Turn images of tables into CSV data. Detect tables from images and run OCR on the cells.

Table of Contents

1. Overview
2. Requirements
3. Demo
4. Modules

Overview

This python package contains modules to help with finding and extracting tabular data from a PDF or image into a CSV format.

Given an image that contains a table…

Extract the the text into a CSV format…

PRIZE,ODDS 1 IN:,# OF WINNERS*
$3,9.09,"282,447"
$5,16.66,"154,097"
$7,40.01,"64,169"
$10,26.67,"96,283"
$20,100.00,"25,677"
$30,290.83,"8,829"
$50,239.66,"10,714"
$100,919.66,"2,792"
$500,"6,652.07",386
"$40,000","855,899.99",3
1,i223,
Toa,,
,,
,,"* Based upon 2,567,700"

Requirements

Along with the python requirements that are listed in setup.py and that are automatically installed when installing this package through pip, there are a few external requirements for some of the modules.

I haven’t looked into the minimum required versions of these dependencies, but I’ll list the versions that I’m using.

• pdfimages 20.09.0 of Poppler
• tesseract 5.0.0 of Tesseract
• mogrify 7.0.10 of ImageMagick

Demo

There is a demo module that will download an image given a URL and try to extract tables from the image and process the cells into a CSV. You can try it out with one of the images included in this repo.

1. pip3 install table_ocr
2. python3 -m table_ocr.demo https://raw.githubusercontent.com/eihli/image-table-ocr/master/resources/test_data/simple.png

That will run against the following image:

The following should be printed to your terminal after running the above commands.

Running `extract_tables.main([/tmp/demo_p9on6m8o/simple.png]).`
Extracted the following tables from the image:
[('/tmp/demo_p9on6m8o/simple.png', ['/tmp/demo_p9on6m8o/simple/table-000.png'])]
Processing tables for /tmp/demo_p9on6m8o/simple.png.
Processing table /tmp/demo_p9on6m8o/simple/table-000.png.
Extracted 18 cells from /tmp/demo_p9on6m8o/simple/table-000.png
Cells:
/tmp/demo_p9on6m8o/simple/cells/000-000.png: Cell
/tmp/demo_p9on6m8o/simple/cells/000-001.png: Format
/tmp/demo_p9on6m8o/simple/cells/000-002.png: Formula
...

Here is the entire CSV output:

Cell,Format,Formula
B4,Percentage,None
C4,General,None
D4,Accounting,None
E4,Currency,"=PMT(B4/12,C4,D4)"
F4,Currency,=E4*C4

Modules

The package is split into modules with narrow focuses.

• pdf_to_images uses Poppler and ImageMagick to extract images from a PDF.
• extract_tables finds and extracts table-looking things from an image.
• extract_cells extracts and orders cells from a table.
• ocr_image uses Tesseract to OCR the text from an image of a cell.
• ocr_to_csv converts into a CSV the directory structure that ocr_image outputs.

The outputs of a previous module can be used by a subsequent module so that they can be chained together to create the entire workflow, as demonstrated by the following shell script.

#!/bin/sh

PDF=$1

python -m table_ocr.pdf_to_images $PDF | grep .png > /tmp/pdf-images.txt
cat /tmp/pdf-images.txt | xargs -I{} python -m table_ocr.extract_tables {}  | grep table > /tmp/extracted-tables.txt
cat /tmp/extracted-tables.txt | xargs -I{} python -m table_ocr.extract_cells {} | grep cells > /tmp/extracted-cells.txt
cat /tmp/extracted-cells.txt | xargs -I{} python -m table_ocr.ocr_image {}

for image in $(cat /tmp/extracted-tables.txt); do
    dir=$(dirname $image)
    python -m table_ocr.ocr_to_csv $(find $dir/cells -name "*.txt")
done

The package was written in a literate programming style. The source code at https://eihli.github.io/image-table-ocr/pdf_table_extraction_and_ocr.html is meant to act as the documentation and reference material.