cMakefile for using tesseract and opencv

Question

I am a newbie to cmake and I am writing an application for using tesseract. the g++ command line work fine

g++ -O3 -std=c++11 `pkg-config --cflags --libs tesseract opencv` my_first.cpp -o my_first

But I wrote the following CMakeFile.txt and building in Clion and it throws a bunch of linking errors

cmake_minimum_required(VERSION 2.6)
add_compile_options(-std=c++11)
project (my_first)

find_package(PkgConfig REQUIRED)
pkg_check_modules (OPENCV REQUIRED opencv)
link_directories(${OPENCV_LIBRARY_DIRS})

pkg_check_modules (TESSERACT REQUIRED tesseract)
link_directories(${TESSERACT_LIBRARY_DIRS})

add_executable(myfirst my_first.cpp)

The following is the error thrown

/usr/local/Cellar/cmake/3.11.3/bin/cmake --build 
/Users/ggovindan/tessaract_ocr/tesseract/experiments/cmake-build-debug --target all -- -j 4
[ 50%] Linking CXX executable myfirst
Undefined symbols for architecture x86_64:
  "cv::Mat::deallocate()", referenced from:
      cv::Mat::release() in my_first.cpp.o
  "cv::String::deallocate()", referenced from:
      cv::String::~String() in my_first.cpp.o
      cv::String::operator=(cv::String const&) in my_first.cpp.o
  "cv::String::allocate(unsigned long)", referenced from:
      cv::String::String(std::__1::basic_string<char, 
std::__1::char_traits<char>, std::__1::allocator<char> > const&) in 
my_first.cpp.o
  "cv::imread(cv::String const&, int)", referenced from:
  _main in my_first.cpp.o
  "cv::fastFree(void*)", referenced from:
    cv::Mat::~Mat() in my_first.cpp.o
  "tesseract::TessBaseAPI::GetUTF8Text()", referenced from:
  _main in my_first.cpp.o
  "tesseract::TessBaseAPI::SetPageSegMode(tesseract::PageSegMode)", referenced from:
  _main in my_first.cpp.o
  "tesseract::TessBaseAPI::Init(char const*, char const*, 
tesseract::OcrEngineMode, char**, int, GenericVector<STRING> const*, 
GenericVector<STRING> const*, bool)", referenced from:
  tesseract::TessBaseAPI::Init(char const*, char const*, 
tesseract::OcrEngineMode) in my_first.cpp.o
  "tesseract::TessBaseAPI::SetImage(unsigned char const*, int, int, int, int)", referenced from:
  _main in my_first.cpp.o
  "tesseract::TessBaseAPI::TessBaseAPI()", referenced from:
  _main in my_first.cpp.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see 
invocation)
make[2]: *** [myfirst] Error 1
make[1]: *** [CMakeFiles/myfirst.dir/all] Error 2
make: *** [all] Error 2

`link_directories(${TESSERACT_LIBRARY_DIRS})` does not add libraries to link. You probably want to look at `target_link_libraries`. — drescherjm, Jun 22 '18 at 19:15
Possible duplicate of [CMake link to external library](https://stackoverflow.com/questions/8774593/cmake-link-to-external-library) — Tsyvarev, Jun 22 '18 at 19:42

saumitra mallick · Answer 1 · 2018-06-27T11:03:25.427

This is what you need to do.Let me know if you face any problems.

set(CMAKE_CXX_STANDARD 14)

set(CMAKE_CXX_STANDARD_REQUIRED ON)

set(CMAKE_CXX_EXTENSIONS OFF)

find_package( PkgConfig REQUIRED)

pkg_search_module( TESSERACT REQUIRED tesseract )

pkg_search_module( LEPTONICA REQUIRED lept )

include_directories( ${TESSERACT_INCLUDE_DIRS} )

include_directories( ${LEPTONICA_INCLUDE_DIRS} )

link_directories( ${TESSERACT_LIBRARY_DIRS} )

link_directories( ${LEPTONICA_LIBRARY_DIRS} )

find_package( OpenCV REQUIRED )

include_directories("myfirst.h")

file(GLOB SOURCES "myfirst.cpp")

add_executable(myfirst ${SOURCES})

target_link_libraries( myfirst ${OpenCV_LIBS} )

target_link_libraries( myfirst ${TESSERACT_LIBRARIES} )

target_link_libraries( myfirst ${LEPTONICA_LIBRARIES} )

#install
install(TARGETS myfirst DESTINATION /usr/local/bin)

cMakefile for using tesseract and opencv

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