Friday, June 5, 2009

How to train Tesseract-OCR

Check out the source code of tesseractindic from Then cd to tesseract_trainer and follow the directions below:

Here is a demonstration of how you can create training data files for an arbitrary language for Tesseract-OCR and subsequently use it to perform OCR.

To create data files for , say, Bengali:

1) Create a directory in tesseract_trainer/ and name it arbitrarily. This contains the symbols of the alphabet. I name it 'beng.alphabet'. In the directory you may create a maximum of 4 files:
a)consonants- Put all the consonants in your script/language in the file. eg, ক , খ (ka, kha) etc
b)pre_semivowels- Put all the semivowels (if any in your script) that come before a consonant. eg, ি, ে, ৈ (e kaar, a kaar, oi kaar )
c)post_semivowels- Put all the semivowels (if any in your script) that come after a consonant, eg, া, ী (aa kaar, ee kaar)
d)rest- Put everything else here, like digits, punctuation, conjuncts, special characters, vowels. You could also choose not to create the 3 files above and put all the symbols in this file.

You need to have some fonts particular to your script installed on your system. On an Ubuntu system you will find them in /usr/share/fonts/truetype/ttf-bengali-fonts/. You will require the name(s) of the fonts later.

Now change directory to tesseract_trainer/ and execute the following on the shell(for bengali for example): python -font Mitra -l Bengali -s 15 -a beng.alphabet/

-font takes the ttf font name you are trying to train
-l takes the script name to be trained as input
-s size of the characters generated in images in Bengali.images/

This command will generate many images and corresponding box files in Bengali.images/. In the end it generates 5 files in Bengali.training_data/.

These 5 files are needed by Tesseract-OCR engine to add a new script support. In addition there are 3 more files required that ae to be created by you separately. These are :

* Bengali.freq-dawg
* Bengali.word-dawg
* Bengali.user-words
You do not require the tesseract_trainer tool to create the files above. They can be created by following appropriate instructions at

Copy these files to /usr/local/share/tessdata and to tessdata/ folder of you tesseract-ocr source code.

Now lets OCR some image. Lets say the image is image.tif. Here is what you must execute at the terminal:

tesseract image.tif ocr -l Bengali

You get ocr.txt as the output.

Contact for clarifications.

Contact for further clarifications.

And yeah, this is work in progress.


  1. lines are not seen fully. i had to copy paste into a text editor. pl look into the issue.

  2. //Then cd to tesseract_trainer and follow the directions below://
    in my ubuntu system where is this directory?
    i installed tesseract through synaptic.