qt creator tesseract ocr problem

Kenengan

Hi, I have some problem with qt creatore. When i make qwidgetapp in visual studio 2019 using qt visual studio tools and i add tesseract/leptonica installed from vcpkg here, then everything wokrs all right (its all dynamic linking via dlls). But in qt creator i cannot add packages from vcpkg.. When I for example add to code:

#include <tesseract/baseapi.h>
#include <leptonica/allheaders.h>
tesseract::TessBaseAPI *api = new tesseract::TessBaseAPI();

and I have in qmake this:

INCLUDEPATH += "D:\vcpkg\installed\x64-windows\include"

then qt creator see header files and if i type for example api->init it see all methods etc.

But when i try run program i have all the time this error: "undefined reference to `tesseract::TessBaseAPI::TessBaseAPI()".

I tried adding lib files with LIBS +=, I also tried copy dll files to folder where executable will be created but nothing work.

Any sugestions what else i can try?

JonB

@Kenengan said in qt creator tesseract ocr problem:

But when i try run program

When you run the program? Do you mean when you try to link it? Please be clear.

I tried adding lib files with LIBS +=,

Show this.

Have a read through:
https://stackoverflow.com/questions/25044448/undefined-reference-to-tesseracttessbaseapitessbaseapi
https://forum.qt.io/topic/137482/qt-undefined-reference-to-tesseract-tessbaseapi-tessbaseapi

Kenengan

By "when i try run program" I mean I run this in debug mode (ctrl + r).
Here is full code, very simple console app, main.cpp:

#include <QCoreApplication>
#include <tesseract/baseapi.h>
#include <leptonica/allheaders.h>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    tesseract::TessBaseAPI *api = new tesseract::TessBaseAPI();

    return a.exec();
}

and here is .pro file:

QT = core

CONFIG += c++17 cmdline

# You can make your code fail to compile if it uses deprecated APIs.
# In order to do so, uncomment the following line.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

SOURCES += \
        main.cpp

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

INCLUDEPATH += "D:\vcpkg\installed\x64-windows\include"
LIBS += -L"D:\vcpkg\installed\x64-windows\debug\lib"
LIBS += -L"D:\vcpkg\installed\x64-windows\debug\bin"
LIBS += -ltesseract55d -lleptonica-1.84.1d

It looks like includepath works just fine but libs+= not work and I dont know why. I also tried diffrent slashes like this "" and this "/", I tried copy lib and dll files to folder with source code (where main.cpp is located) and libs+= them directly, I also tried some others things that I found on internet but there is still same error: "undefined reference to `tesseract::TessBaseAPI::TessBaseAPI()'".

SGaist

Hi,

Are you sure that:

you are linking to the correct libraries ?
these libraries are of the correct architecture ?
the compiler used for these libraries is the same as for your application ?

JonB

@Kenengan said in qt creator tesseract ocr problem:

By "when i try run program" I mean I run this in debug mode (ctrl + r).

I am still not convinced that you are reporting a runtime error rather than a link time one. You are a C++ developer so you must know the difference. Do not use Ctrl+R/Run, as this will first try to compile and link and may report an error there --- since you don't show us the Output from Creator we do not know how far you got. First do a complete Rebuild and tell us whether that completes successfully or reports an error before you get as far as tyring to run. I am not a Windows or MSVC user, but so far as I know

error: "undefined reference to `tesseract::TessBaseAPI::TessBaseAPI()".

will come from the linker, I don't think you would such an error at runtime? Let's establish that first before analyzing any further,

JonB

@Kenengan said in qt creator tesseract ocr problem:

LIBS += -L"D:\vcpkg\installed\x64-windows\debug\lib"
LIBS += -L"D:\vcpkg\installed\x64-windows\debug\bin"
LIBS += -ltesseract55d -lleptonica-1.84.1d

P.S.
I am concerned by these lines. I do not use MSVC so cannot be sure about this. Using -L..., and in particular -l... certainly is correct for Linux/gcc or MinGW under Windows. However you say you are using MSVC, and its LINK linker. I didn't think that accepts -L or -l for libraries? I'm not sure about -L equivalent if you need it it (/LIBPATH?), and I thought libraries are supplied by a filename/path ending in .lib? So are you following instructions for MinGW/gcc rather than for MSVC? Or are these lines indeed correct (somehow) for MSVC?

Kenengan

I found solution, the problem was - I make console app in qt creator with mingw compiler, but tesseract and leptonica was build by vcpkg with msvc compiler. When I try link them to console app then I got this error I post above.

If I switch mingw in qt creator to msvc then these libs works all right. I also rebuild tesseract and leptonica with mingw and link them to console app also using mingw and it also work just fine.

So it was my fault, I use another compiler to build app (mingw) and another to build libraries (msvc), but thanks for help, now everything works good and I can keep working on my application.