adf2pdf 0.8.3
Automate the workflow around ADF scanning, OCR and PDF creation
Requires Python: >=3
Keywords: adf scanning sane duplex-scanning ocr tesseract pdf

adf2pdf - a tool that turns a batch of paper pages into a PDF
with a text layer.  By default, it detects empty pages (as they
may easily occur during duplex scanning) and excludes them from
the OCR and the resulting PDF.

For that, it uses [Sane's][5] [scanimage][6] for the scanning,
[Tesseract][4] for the [optical character recognition][ocr] (OCR), and
the Python packages [img2pdf][9], [Pillow (PIL)][10] and
[PyPDF2][11] for some image-processing tasks and PDF mangling.


Example:

    $ adf2pdf contract-xyz.pdf

2017, Georg Sauthoff <mail@gms.tf>

## Features

- Automatic document feed (ADF) support
- Fast empty page detection
- Overlaying of scanning, image processing, OCR and PDF creation
  to minimize the total runtime
- Fast creation of small PDFs using the fine [img2pdf][9] package
- Only use of safe compression methods, i.e. no error-prone
  symbol segmentation style compression like [JBIG2][12] or JB2
  that is used in [Xerox photocopiers][12] and the DjVu format.

## Install Instructions

Adf2pdf can be directly installed with [`pip`][13], e.g.

    $ pip3 install --user adf2pdf

or

    $ pip3 install adf2pdf

See also the [PyPI adf2pdf project page][14].

Alternatively, the Python file `adf2pdf.py` can be directly
executed in a cloned repository, e.g.:

    $ ./adf2pdf.py report.pdf

In addition to that, one can install the development version from
a cloned work-tree like this:

    $ pip3 install --user .

## Hardware Requirements

A scanner with automatic document feed (ADF) that is supported by
Sane. For example, the [Fujitsu ScanSnap S1500][1] works
well. That model supports duplex scanning, which is quite
convenient.

## Example continued

Running _adf2pdf_ for a 7 page example document takes 150 seconds
on an i7-6600U (Intel Skylake, 4 cores) CPU (using the ADF of the
Fujitsu ScanSnap S1500). With the defaults, _adf2pdf_ calls
`scanimage` for duplex scanning into 600 dpi lineart (black and
white) images. In this example, 6 pages are empty and thus
automatically excluded, i.e. the resulting PDF then just contains
8 pages.

The resulting PDF contains a text layer from the OCR such that
one can search and copy'n'paste some text. It is 1.1 MiB big,
i.e. a page is stored in 132 KiB, on average.

## Software Requirements

The script assumes Tesseract version 4, by default. Version 3 can
be used as well, but the [new neural network system in Tesseract
4][8] just performs magnitudes better than the old OCR model.
Tesseract 4.0.0 was released in late 2018, thus, distributions
released in that time frame may still just include version 3 in
their repositories (e.g. Fedora 29 while Fedora 30 features version
4). Since version 4 is so much better at OCR I can't recommend it
enough over the stable version 3.

Tesseract 4 notes (in case you need to build it from the sources):

- [Build instructions][2] - warning: if you miss the
  `autoconf-archive` dependency you'll get weird autoconf error
  messages
- [Data files][3] - you need the training data for your
  languages of choice and the OSD data

Python packages:

- [img2pdf][9] (Fedora package: python3-img2pdf)
- [Pillow (PIL)][10] (Fedora package: python3-pillow-devel)
- [PyPDF2][11] (Fedora package: python3-PyPDF2)

[1]: http://www.fujitsu.com/us/products/computing/peripheral/scanners/product/eol/s1500/
[2]: https://github.com/tesseract-ocr/tesseract/wiki/Compiling-–-GitInstallation
[3]: https://github.com/tesseract-ocr/tesseract/wiki/Data-Files
[4]: https://en.wikipedia.org/wiki/Tesseract_(software)
[5]: https://en.wikipedia.org/wiki/Scanner_Access_Now_Easy
[6]: http://www.sane-project.org/man/scanimage.1.html
[7]: https://en.wikipedia.org/wiki/Optical_character_recognition
[8]: https://github.com/tesseract-ocr/tesseract/wiki/NeuralNetsInTesseract4.00
[9]: https://pypi.org/project/img2pdf/
[10]: http://python-pillow.github.io/
[11]: https://github.com/mstamy2/PyPDF2
[12]: https://en.wikipedia.org/wiki/JBIG2
[13]: https://en.wikipedia.org/wiki/Pip_(package_manager)
[14]: https://pypi.org/project/adf2pdf/
[ocr]: https://en.wikipedia.org/wiki/Optical_character_recognition