OCRFeeder (FOSDEM 2010)

OCRFeeder

static void
_f_do_barnacle_install_properties(GObjectClass
*gobject_class)
{
GParamSpec *pspec;
/* Party code attribute */
pspec = g_param_spec_uint64
(F_DO_BARNACLE_CODE,
"Barnacle code.",
"Barnacle code",
0,
G_MAXUINT64,
G_MAXUINT64 /*
default value */,
G_PARAM_READABLE
| G_PARAM_WRITABLE |
G_PARAM_PRIVATE);

Documents conversion on GNOME

g_object_class_install_property (gobject_class,
F_DO_BARNACLE_PROP_CODE,

Joaquim Rocha
jrocha@igalia.com

FOSDEM 2010

What is it?
Document Analysis and Optical
Character Recognition
for GNOME

Joaquim Rocha (Igalia) · OCRFeeder · FOSDEM 2010

Why is it?
Paper has a number of problems
No applications for GNU/Linux to do
a fair job


Paper problems:
Security


CC Photo by: http://www.flickr.com/photos/badwsky/

Paper problems:
Preservation


CC Photo by: http://www.flickr.com/photos/98469445@N00/

Paper problems:
Data processing


CC Photo by: http://www.flickr.com/photos/hugovk/

Paper problems:
Ecology


CC Photo by: http://www.flickr.com/photos/pranavsingh/

No fair conversion apps for
GNU/Linux
apart from OCR engines, but...


OCR != Document Conversion
(it only deals with chars)
(does not consider the layout)
(does not distinguish contents)


what you want is
Document Analysis and
Recognition
(conversion of documents to an
electronic format)
(first projects in the 80s)

Where are were we at?
* Some closed solutions
* Only for proprietary systems
* Various prices
* still... arguable results


How?


How


Base concept:
1. Clip the contents
2. Classify them
2.1. They are graphics → Paste on
document
2.2. They are text → Calculate letter
size; paste on document

So many layouts...


CC Photo by: http://www.flickr.com/photos/uber-tuber/

Layouts vary with the type of
document
What works on detecting one, won't
work on others


OCRFeeder focus on contents, not
on layouts!


Key concept:
If a document image can be
divided in windows of 1 (content)
or 0 (not content),
then it is possible to group all the
1s and outline the contents

Sliding Window Algorithm:
1. A NxN pixel window runs through
the document top to bottom, left to
right


2. For every iteration, if there's a
pixel inside the window which
contrasts with the background,
then the window gets a 1,
otherwise it gets a 0

It does not check all the pixels so
there is a better performance


3. After all windows
have a value assigned,
the ones with the value 1 are
grouped


4. Every time a set of 1s is
grouped, each window is
reassigned the value 0
(these are called blocks)

5. When all windows have
the value 0, the algorithm
reached the end


Block structure:


Joining Blocks:
Blocks are check with each other
and joined when appropriate
When no blocks can be joined the
analysis part is finished


Recognition:
System-wide OCR engines are used
Engines are configured from the
GUI or XML files


Engine configuration:
<?xml version="1.0" encoding="UTF-8"?>
<engine>
<name>Tesseract</name>
<image_format>TIFF</image_format>
<engine_path>/usr/bin/tesseract</engine_path>
<arguments>$IMAGE $FILE; cat $FILE.txt;
rm $FILE.txt</arguments>
</engine>


Classification:
It is graphics if:
* Text is empty
* More than 50% of the chars are
failure chars, punctuation or spaces

Font Size Detection:
“Measures” in pixels the size of
each text line

Although it results in different
sizes...

The value equal or greater than the
average is chosen
(results in values equal or close to
the original font size)

The font size is calculated in inches
using the resolution (DPI)
(if there's no resultion info, assume
300 DPI)
The value is then divided by the
DTP (DeskTop Publishing point): 72

Exportation to ODT:
Uses ODFPy
(abstracts ODF creation)
(just above XML)


User interaction:
Users can edit everything
and review the algorithm's results
So, UI can work in attended and
unattended ways
CLI only works in an unattended
mode

ABBY Finereader test

Nuance Omnipage test


Finereader's
results
Omnipage's
results


Demo time!


Other features:
* PDF importation
* Unpaper preprocessor
* Font style edition
* Exportation to HTML
* Project saving/loading

Future:
* Integrate Ocropus as an
alternative analysis backend
* More exportation formats: HOCR,
txt, PDF
* Improved a11y
* Better integration with GNOME
and other GNOME apps

GNOME:
Development moved to GNOME's
infrastructure since last month


Webpage:
http://live.gnome.org/OCRFeeder
git:
http://git.gnome.org/ocrfeeder
Bugzilla:
coming soon...

Thank you!

OCRFeeder (FOSDEM 2010)

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