Build Tesseract OCR library 3.02.02 with Qt 5.1 on Windows

The different steps in this article have been done:

• under Windows 7 Home Premium.
• with Qt 5.1.

Tesseract OCR source code

Download tesseract-ocr-3.02.02.tar.gz and extract it.

Leptonica library

From the Leptonica web site:

Leptonica is a pedagogically-oriented open source site containing software that is broadly useful for image processing and image analysis applications.

Leptonica is quite tedious to build because of all its dependencies. Fortunately, someone did this work for us.

Here is the link to his repository: https://github.com/zdenop/tesseract-mingw .

Many thanks to zdenop for saving us time!

Download the following libraries from the bin folder:

• libgif-4.dll
• libjbig-1.dll
• libjpeg-8.dll
• liblept-3.dll : the Leptonica library.
• libpng15-15.dll
• libtiff-3.dll
• libtiffxx-3.dll
• libwebp-2.dll
• zlib1.dll

Maybe, you've noticed that a libtesseract-3.dll is also available. I've tried to use it in my projects but it didn't work. That's why I've decided to build it my way.

You must also get the source code. I didn't use the header files in zdenop's repo but you could try. I used the original headers from Leptonica version 1.69.

Extract Leptonica archive, create a bin directory in the new folder then copy all the libraries mentioned above in it.

tesseract-ocr.pro file

In this section, we won't analyze the whole file but only the lines you will have to understand.

#_-_-_-_-_-_SOME DIRECTORIES_-_-_-_-_-_
OCR_DIR = D:/prog/ocr
LEPTONICA_DIR = $$OCR_DIR/leptonica-1.69
MINGW_LIB_DIR = D:/Programs/Qt/Qt5.1.0/Tools/mingw48_32/i686-w64-mingw32/lib
#-_-_-_-_-_-

• OCR_DIR : base directory for my OCR tools.
• LEPTONICA_DIR : Leptonica extraction directory.
• MINGW_LIB_DIR : this one is needed to link against winsock2 library.

DESTDIR = ../tesseract-ocr_release

The build output directory.

DEFINES += _tagBLOB_DEFINED
DEFINES += USE_STD_NAMESPACE
DEFINES += WINDLLNAME=\\\"$$TARGET.dll\\\"

Here, we add preprocessor definitions.

• _tagBLOB_DEFINED : to avoid conflicting declarations between wtypes.h (MinGW) and platform.h (tesseract) if you work with Qt.
• USE_STD_NAMESPACE : I have not searched its exact purpose but it must be declared.
• WINDLLNAME : used by ccutil files.

#_-_-_-_-_-_LINKING_-_-_-_-_-_
win32:LIBS += $$LEPTONICA_DIR/bin/liblept-3.dll
win32:LIBS += $$MINGW_LIB_DIR/libws2_32.a
#-_-_-_-_-_-

Linking against Leptonica and winsock2 libraries.

tesseract-ocr.pro can be downloaded from my repository:

https://github.com/broija/tesseract_ocr_qt