1. Tesseract OCR Engine Svetlin Nakov and Veselin Kolev www.devbg.org
BASD (Bulgarian Association of Software Developers)

2. Hot News!
Microsoft Corporation just announced its strategic partnership with OpenFest
OpenFest is upgrading to Windows 7 and MS SQL Server 2008 = +

3. What is OCR? Stands for Optical Character Recognition
Extracts the text from a given image

4. What is OCR? (2) Invented by Gustav Tauschek
Tauschek obtained a patent on OCR
1929 in Germany
1935 in USA
Tauschek’s machine
Was a mechanical device
Uses templates, light and photodetector
When a light was directed towards the templates no light reach the photodetector

5. What is OCR? (3)
OCR Predicates electronic computers!

6. Project Tesseract History of Tesseract Open source OCR engine
Developed by HP between 1985 and 1995
Never used in an HP product
Rated highly at The Fourth Annual Test of OCR Accuracy in 1995
In 2005 HP transferred Tesseract to the ISRI and released it as open source
ISRI == Information Science Research Institute
The development is currently led by Google

7. Project Tesseract (2)
Tesseract is an OCR Engine and is NOT a complete OCR program
Originally intended to serve as a component part of other programs
Works from the command line
Has no page layout analysis (will have soon)
Has no output formatting
Has no GUI

8. Tesseract Versions Stable build – version 2.04
Has some documentation
Can be easily trained on a new language
Has memory leaks
Development version – 3.0 (unstable)
Not documented, unstable
Language files are not compatible (need special conversion)

9. Downloading, Compiling and Running Tesseract
Demo
Downloading, Compiling and Running Tesseract
(Latest Version)

10. How Tesseract Works? Adaptive thresholding on the input image
Analyze connected components in the binary image
Find text lines and words
First pass of recognition process
Attempts to recognize each word in turn
Satisfactory words are passed to adaptive trainer
Lessons learned are employed in a second pass
Used for words not satisfactory recognized
Producing the output text

11. Training Tesseract Prepare training images and .box files
Files: lang.tif and lang.box
2.04 supports only uncompressed TIFFs
.box files contain characters with coordinates
Extract the character features
This produces lang.tr
Perform character clustering
tesseract lang.tif junk nobatch box.train
mftraining lang.tr
cntraining lang.tr

12. Training Tesseract (2) Compute the character set properties
isLetter, isDigit, isUpper, isPunctuation, …
Unicode provides this information
Train language dictionaries
List of all words in the target language
List of the most frequent words
unicharset_extractor lang.box
wordlist2dawg freq-words.txt lang.freq-dawg
wordlist2dawg all-words.txt lang.word-dawg

13. Training Tesseract for Bulgarian and English
Demo
Training Tesseract for Bulgarian and English
(Bulgarian for IT Professionals)

14. Other OCR Engines OCRopus Open source document analysis and OCR system
Also funded by Google
Provides much of the layout analysis functionality missing from Tesseract
Capable to use engines other than Tesseract

15. Other OCR Engines (2) ABBYY FineReader OCR
Supports a big number of features
Known for its highly accuracy
Commercial
Microsoft Office Document Imaging (MODI)
Supports editing documents scanned by Microsoft Office Document Scanning
It was firstly introduced in MS Office XP

16. Commercial OCR vs. Tesseract
100+ languages
Accuracy is good now
Sophisticated app with complex UI
Works on complex magazine pages
Windows mostly
Costs $130-$500
6 languages
Accuracy was good in 1995
No UI yet
Page layout analysis coming soon
Running on Linux, Mac, Windows, more..
Open source – Free!

17. Tesseract Future Page layout analysis More languages Improve accuracy
Add a UI
Support for connected scripts (like Arabian)

18. Links For more information see: Speakers
downloads/tesseract_overview.pdf
Speakers

19. Tesseract OCR
Questions?