Presentation is loading. Please wait.

Presentation is loading. Please wait.

Tesseract OCR Engine Svetlin Nakov and Veselin Kolev

Similar presentations

Presentation on theme: "Tesseract OCR Engine Svetlin Nakov and Veselin Kolev"— Presentation transcript:

1 Tesseract OCR Engine Svetlin Nakov and Veselin Kolev
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 2.04 supports only uncompressed TIFFs .box files contain characters with coordinates Extract the character features This produces Perform character clustering tesseract lang.tif junk nobatch box.train mftraining cntraining

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 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?

Download ppt "Tesseract OCR Engine Svetlin Nakov and Veselin Kolev"

Similar presentations

Ads by Google