CMakeLists.txt與OpenCV

在Linux下安裝了兩個版本的Opencv，一個2.4.9在默認路徑下：

/usr/local/share/OpenCV/OpenCVConfig.cmake

一個3.4.9安裝在自定義路徑下：

/usr/local/include/opencv3.4.9/share/OpenCV/OpenCVConfig.cmake

在調用自定義的opencv版本時CMakeLists.txt內容如下：

# cmake needs this line
cmake_minimum_required (VERSION 2.8) 
# Define project name
project(TestOpencv)  

# Find OpenCV, you may need to set OpenCV_DIR variable
# to the absolute path to the directory containing OpenCVConfig.cmake file
# via the command line or GUI
set(OpenCV_DIR /usr/local/include/opencv3.4.9/share/OpenCV)
find_package(OpenCV 3 REQUIRED)
message(STATUS "Opencv library status: ")
message(STATUS "> version: ${OpenCV_VERSION} ")
message(STATUS "> libraries: ${OpenCV_LIBS}")
message(STATUS "> include: ${OpenCV_INCLUDE_DIRS} ")

# Add OpenCV headers location to your include paths
include_directories(${OpenCV_INCLUDE_DIRS})


# Declare the executable target built from your sources
add_executable(main main.cpp)

# Link your application with OpenCV libraries
target_link_libraries(main ${OpenCV_LIBS})

其中line 9 很重要，如果沒有set 路徑的話會找到默認路徑下的opencv 2.4.9，從而不匹配 find_package(OpenCV 3 REQUIRED) 而報錯。

如果只是用opencv2.4.9就不需要line 9,然后 find_package(OpenCV 3 REQUIRED) 改成 find_package(OpenCV 2 REQUIRED) 或  find_package(OpenCV  REQUIRED)

文件路徑結構：

|--build
|
|--CMakeLists.txt
|
|--main.cpp
|
|--test
　　|
　　|--1.jpg

其中build是新建的文件夾。

main.cpp內容如下：

#include <stdio.h>
#include "opencv2/opencv.hpp"

int main()
{
   cv::Mat image = cv::imread("../test/1.jpg");      
    printf("image.col=%d image.raw=%d \n", image.cols, image.raws);
    
    cv::imshow("picture",image);
    cv::waitKey(0);
    return 0;

}

在build目錄下執行：

cmake ..

生成nakefile文件，接着執行編譯命令：

make

這樣會生成一個可執行程序 main

執行程序：

./main