finereader in Medak, Sekulic & Mertens 2014
TER RECOGNITION
Before the edited-down graphic files are finalized as an e-book, we want to transform the image of
the text into an actual text that can be searched, highlighted, copied and transformed. That
functionality is provided by Optical Character Recognition. This a technically difficult task dependent on language, script, typeface and quality of print - and there aren't that many OCR tools
that are good at it. There is, however, a relatively good free software solution - Tesseract
(http://code.google.com/p/tesseract-ocr/) - that has solid performance, good language data and can
be trained for an even better performance, although it has its problems. Proprietary solutions (e.g.
Abby FineReader) sometimes provide superior results.
Tesseract supports as input format primarily .tiff files. It produces a plain text file that can be, with
the help of other tools, embedded as a separate layer under the original graphic image of the text in
a PDF file.
With the help of other tools, OCR can be performed also against other input files, such as graphiconly PDF files. This produces inferior results, depending again on the quality of graphic files and
the reproduction of text in them. One such tool is a bashscript to OCR a ODF file that can be found
here: https://github.com/andrecastro0o/ocr/blob/master/ocr.sh
As mentioned in the 'before scanning' section, the quality of the original book wil
completed, the resulting text can be merged with
the images of pages and output into an e-book format. While increasingly the proper e-book file
formats such as ePub have been gaining ground, PDFs still remain popular because many people
tend to read on their computers, and they retain the original layout of the book on paper including
the absolute pagination needed for referencing in citations. DjVu is also an option, as an alternative
to PDF, used because of its purported superiority, but it is far less popular.
The export to PDF can be done again with a number of tools. In our case we'll complete the optical
character recognition and PDF export in gscan2pdf. Again, the proprietary Abbyy FineReader will
produce a bit smaller PDFs.
If you prefer to use an e-book format that works better with e-book readers, obviously you will have
to remove some of the elements that appear in the book - headers, footers, footnotes and pagination.
This can be done earlier in the process of cropping down the original .jpg image files (see under III)
or later by transforming the PDF files. This can be done in Calibre (http://calibre-ebook.com) by
converting the PDF into an ePub, where it can be further tweaked to better accommodate or remove
the headers, footers, footnotes and pagination.
Optical character recognition and PDF export in Public Library workflow
Optical character recognition with the Tesser
be performed on GNU/Linux by a
number of command line and GUI tools. Much of those tools exist also for other operating systems.
For the users of the Public Library workflow, we recommend using gscan2pdf application both for
the optical character recognition and the PDF or DjVu export.
To do so, start gscan2pdf and open your .tiff files. To OCR them, go to 'Tools' and select 'OCR'. In
the dialog box select the Tesseract engine and your language. 'Start OCR'. Once the OCR is
finished, export the graphic files and the OCR text to PDF by selecting 'Save as'.
However, given that sometimes the proprietary solutions produce better results, these tasks can also
be done, for instance, on the Abbyy FineReader running on a Windows operating system running
inside the Virtual Box. The prerequisites are that you have both Windows and Abbyy FineReader
you can install in the Virtual Box. If using Virtual Box, once you've got both installed, you need to
designate a shared folder in your Virtual Box and place the .tiff files there. You can now open them
from the Abbyy FineReader running in the Virtual Box, OCR them and export them into a PDF.
To use Abbyy FineReader transfer the output files in your 'out' out folder to the shared folder of the
VirtualBox. Then start the VirtualBox, start Windows image and in Windows start Abbyy
FineReader. Open the files and let the Abbyy FineReader read the files. Once it's done, output the
result into PDF.
VI. CATALOGING AND SHARING THE E-BOOK
Your road from a book on paper to an e-book is complete. If you want to maintain your library you
can use Calibre, a free software tool for e-book library management. You can add the metadata to
your book using the existing catalogues or you can enter metadata manually.
Now you may want to distribute your book. If the work you've digitized is in the public domain
(https://en.wikipedia.org/wiki/Public_domain), you might consider contributing it to the Gutenberg
project
(http://www.gutenberg.org/wiki/Gutenberg:Volunteers'_FAQ#V.1._How_do_I_get_started_as_a_Pr
oject_Gutenberg_volunteer.3F ), Wikib
ess 'Play' button under 'Output'. Save the project.
IV. Optical character recognition & V. Creating a finalized e-book file
If using all free software:
1) open gscan2pdf (if not already installed on your machine, install gscan2pdf from the
repositories, Tesseract and data for your language from https://code.google.com/p/tesseract-ocr/)
- point gscan2pdf to open your .tiff files
- for Optical Character Recognition, select 'OCR' under the drop down menu 'Tools',
select the Tesseract engine and your language, start the process
- once OCR is finished and to output to a PDF, go under 'File' and select 'Save', edit the
metadata and select the format, save
If using non-free software:
2) open Abbyy FineReader in VirtualBox (note: only Abby FineReader 10 installs and works with some limitations - under GNU/Linux)
- transfer files in the 'out' folder to the folder shared with the VirtualBox
- point it to the readied .tiff files and it will complete the OCR
- save the file
REFERENCES
For more information on the book scanning process in general and making your own book scanner
please visit:
DIY Book Scanner: http://diybookscannnner.org
Hacker Space Bruxelles scanner: http://hackerspace.be/ScanBot
Public Library scanner: http://www.memoryoftheworld.org/blog/2012/10/28/our-belovedbookscanner/
Other scanner builds: http://wiki.diybookscanner.org/scanner-build-list
For more information on automation:
Konrad Voeckel's post-processing script (Fr
Display 200 300 400 500 600 700 800 900 1000 ALL characters around the word.