Generating a CMake script file

Before we start creating our source file, we are going to generate the CMakeLists.txt file to allow us to compile our project, structure it, and execute it. The following CMake script is simple and basic but enough to compile and generate the executable:

cmake_minimum_required (VERSION 3.0)

PROJECT(Chapter4_Phototool)

set (CMAKE_CXX_STANDARD 11)

# Requires OpenCV
FIND_PACKAGE( OpenCV 4.0.0 REQUIRED )
MESSAGE("OpenCV version : ${OpenCV_VERSION}")

include_directories(${OpenCV_INCLUDE_DIRS})
link_directories(${OpenCV_LIB_DIR})

ADD_EXECUTABLE(${PROJECT_NAME} main.cpp)
TARGET_LINK_LIBRARIES(${PROJECT_NAME} ${OpenCV_LIBS})

The first line indicates the minimum CMake version required to generate our project, the second one sets the project name that we can use as the ${PROJECT_NAME} variable, and the third one sets the required C++ version; in our case, we require the C++11 version, as we can see in the next snippet:

cmake_minimum_required (VERSION 3.0)

PROJECT(Chapter4_Phototool)

set (CMAKE_CXX_STANDARD 11)

Moreover, we require the OpenCV library. First, we need to find the library, and then we'll show a message on the OpenCV library version found with the MESSAGE function:

# Requires OpenCV 
FIND_PACKAGE( OpenCV 4.0.0 REQUIRED ) 
MESSAGE("OpenCV version : ${OpenCV_VERSION}") 

If the library, with a minimum version of 4.0, is found, then we include the headers and library files in our project:

include_directories(${OpenCV_INCLUDE_DIRS}) 
link_directories(${OpenCV_LIB_DIR})

Now, we only need to add the source files to compile and link with the OpenCV library. The project name variable is used as the executable name, and we use only a single source file, called main.cpp:

ADD_EXECUTABLE(${PROJECT_NAME} main.cpp) 
TARGET_LINK_LIBRARIES(${PROJECT_NAME} ${OpenCV_LIBS})