August 31, 2016

Using Tesseract on Ubuntu

In this tutorial, I will show you how to install and use Google’s Open Source OCR engine Tesseract. First off, let’s discuss step by step procedure to install Tesseract on Ubuntu.

1. Installation

1.1 Installing Dependencies

First of all we need to install all the dependencies that are required by Tesserect. Please do not skip any command.

$ sudo apt-get install libpng-dev libjpeg-dev libtiff-dev zlib1g-dev
$ sudo apt-get install gcc g++
$ sudo apt-get install autoconf automake libtool checkinstall

We need image processing toolkit Leptonica to build Tesseract. During the writing of this tutorial, the latest version of Leptonica was 1.73, please check Leptonica's official website for the latest version. Installing the latest version is highly recommended.

$ cd ~
$ wget http://www.leptonica.org/source/leptonica-1.73.tar.gz
$ tar -zxvf leptonica-1.73.tar.gz
$ cd leptonica-1.73 
$ ./configure
$ make
$ sudo checkinstall
$ sudo ldconfig

1.2 Compiling Tesseract

First make sure that you have git installed on your machine. If not, you can install it by running:

$ sudo apt-get install git

Now clone Tesseract and build it.

$ cd ~ 
$ git clone https://github.com/tesseract-ocr/tesseract.git
$ cd tesseract
$ ./autogen.sh
$ ./configure
$ make
$ sudo make install 
$ sudo ldconfig

1.3 Installing Language Components

Now download English language data for the OCR engine:

$ cd ~
$ git clone https://github.com/tesseract-ocr/tessdata.git 
$ sudo mv ~/tessdata/* /usr/local/share/tessdata/

Tesserect has finally been installed and configured! Now let’s run it.

2. Running It

Select an image with a text, and then run this command in the console (assuming img.png is the input filename):

$ tesseract img.png out

The text read will be saved in out.txt file in the same folder. 

3. Using Python and Tesserect

Python-tesseract is a python wrapper for google’s Tesseract-OCR. First to install pip, follow these instructions.

$ sudo apt-get update
$ sudo apt-get -y install python-pip

Then to install pytesseract,

$ sudo pip install pytesseract

ALTERNATIVELY, if you want to download and install it from its source:

$ git clone git@github.com:madmaze/pytesseract.git 
$ sudo python setup.py install

Now let’s write a simple python program to read a simple captcha:

from pytesseract import image_to_string 
import Image
print image_to_string(Image.open('captcha.png'))

Then,

$ python test.py
be5f

Assuming you named it test.py, the output text will be printed on your screen.


This article was contributed by a student at Holberton School

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