用C ++创建一个共享库以与Python集成

Question

I need to generate a .so using this code in C++, to integrate with Python:

#include <tesseract/baseapi.h>
#include <leptonica/allheaders.h>
// sudo apt-get install libtesseract-dev
// sudo apt-get install libleptonica-dev

extern "C" void read(void) {
    Pix *image = pixRead("/home/macabeus/test.jpg");

    tesseract::TessBaseAPI *api = new tesseract::TessBaseAPI();
    api->Init(NULL, "eng");
    api->SetImage(image);
    api->SetVariable("save_blob_choices", "T");
    api->SetVariable("tessedit_char_whitelist", "QWERTYUIOPASDFGHJKLZXCVBNM");
    api->Recognize(NULL);

    tesseract::ResultIterator* ri = api->GetIterator();
    tesseract::PageIteratorLevel level = tesseract::RIL_SYMBOL;
    if(ri != 0) {
        do {
            const char* symbol = ri->GetUTF8Text(level);
            if(symbol != 0) {
                tesseract::ChoiceIterator ci(*ri);
                do {
                    const char* choice = ci.GetUTF8Text();
                    printf("%s(%f)..", choice, ci.Confidence());
                } while(ci.Next());
                printf("--> recognized as '%s'\n", symbol);
            }
            delete[] symbol;
        } while((ri->Next(level)));
    }
}

I use the following command in the terminal to generate the file .so :

g++ main.cpp -c -fPIC -o main.o
g++ -shared -o main.so main.o

Then generates the file

main.so: ELF 64-bit LSB  shared object, x86-64, version 1 (SYSV), dynamically linked, BuildID[sha1]=616e7e8e8a094b9c075a21897e8c5d32fc6ea159, not stripped

So, in Python, I use ctypes to use the shared object:

import ctypes

c_lib_test = ctypes.CDLL('cppcodetesseract/main.so')

However, I received the following error message when running code in Python:

[...]
  File "/home/macabeus/ApenasMeu/Dropbox/Python/Extending with C/main.py", line 5, in <module>
    c_lib_tes = ctypes.CDLL('cppcodetesseract/main.so')
  File "/usr/lib/python3.4/ctypes/__init__.py", line 351, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: cppcodetesseract/main.so: undefined symbol: _ZN9tesseract14ChoiceIterator4NextEv

How to solve it? I got success in other codes in C++ that did not use tesseract or leptonica. But when I use these libraries, I can not succeed.

Answer 1

I resolved my problem: cmake

I created the file CMakeList.txt with:

add_library(foo SHARED main.cpp)
target_link_libraries (foo  lept tesseract)

And so I used the commands cmake . and make . Then went generated the file libfoo.so . It worked perfectly.