ccextractor/docs/OCR.md

Overview

OCR (Optical Character Recognition) is a technique used to extract text from images. In the World of Subtitle, subtitle stored in bitmap format are common and even necessary. For converting subtitle in bitmap format to subtitle in text format OCR is used.

Dependency

1. Tesseract (OCR library by Google)
2. Leptonica (Image processing library)

How to compile CCExtractor on Linux with OCR

Install Dependency

Using package manager

Ubuntu, Debian

sudo apt-get install libleptonica-dev libtesseract-dev tesseract-ocr-eng

Suse

zypper install leptonica-devel

Downloading source code and compiling it.

Leptonnica.

This package is available in your distro, you need liblept-devel library.

If Leptonica isn't available for your distribution, or you want to use a newer version than they offer, you can compile your own.

you can download lib leptonica source code from http://www.leptonica.com/download.html

Tesseract.

Tesseract is available directly from many Linux distributions. The package is generally called 'tesseract' or 'tesseract-ocr' - search your distribution's repositories to find it. Packages are also generally available for language training data (search the repositories,) but if not you will need to download the appropriate training data, unpack it, and copy the .traineddata file into the 'tessdata' directory, probably /usr/share/tesseract-ocr/tessdata or /usr/share/tessdata.

If Tesseract isn't available for your distribution, or you want to use a newer version than they offer, you can compile your own.

If you compile Tesseract then following command in its source code are enough

./autogen.sh
./configure
make
sudo make install
sudo ldconfig

Note:

1. CCExtractor is tested with Tesseract 3.04 version but it works with older versions.
2. Useful Download links:
   1. Tesseract https://github.com/tesseract-ocr/tesseract/archive/3.04.00.tar.gz
   2. Tesseract training data https://github.com/tesseract-ocr/tessdata/archive/3.04.00.tar.gz

##Compilation

###using Build script

cd ccextractor/linux
./build

Passing flags to configure

cd ccextractor/linux
./autogen.sh
./configure --with-gui --enable-ocr
make

Passing flags to cmake

cd <CCExrtactor cloned code>
mkdir build
cd build
cmake -DWITH_OCR=ON ../src
make

How to compile CCExtractor on Windows with OCR

Download prebuild library of leptonica and tesseract from following link
https://drive.google.com/file/d/0B2ou7ZfB-2nZOTRtc3hJMHBtUFk/view?usp=sharing

put the path of libs/include of leptonica and tesseract in library paths.

1. In visual studio 2013 right click and select property.
2. Select Configuration properties in left panel(column) of property.
3. Select VC++ Directory.
4. In the right pane, in the right-hand column of the VC++ Directory property, open the drop-down menu and choose Edit.
5. Add path of Directory where you have kept uncompressed library of leptonica and tesseract.

Set preprocessor flag ENABLE_OCR=1

1. In visual studio 2013 right click and select property.
2. In the left panel, select Configuration Properties, C/C++, Preprocessor.
3. In the right panel, in the right-hand column of the Preprocessor Definitions property, open the drop-down menu and choose Edit.
4. In the Preprocessor Definitions dialog box, add ENABLE_OCR=1. Choose OK to save your changes.

Add library in linker

1. Open property of project
2. Select Configuration properties
3. Select Linker in left panel(column)
4. Select Input
5. Select Additional dependencies in right panel
6. Add libtesseract304d.lib in new line
7. Add liblept172.lib in new line

Download language data from following link
https://code.google.com/p/tesseract-ocr/downloads/list
after downloading the tesseract-ocr-3.02.eng.tar.gz extract the tar file and put
tessdata folder where you have kept CCExtractor executable

Copy the tesseract and leptonica dll from lib folder downloaded from above link to folder of executable or in system32.