‘CV

在编译时提示找不到opencv相关标志：
‘CV_LOAD_IMAGE_GRAYSCALE’ was not declared in this scope
CV_LOAD_IMAGE_UNCHANGED’ was not declared in this scope
‘CV_MINMAX’ was not declared in this scope

原因是作者代码使用的opencv版本是3.x，而自己默认的opencv版本是4.4.0，在新版本中相关的定义已经发生了变化，解决办法有两个：
方法一：
碰巧自己电脑也装了opencv3.2，该一下代码默认使用的opencv版本就好了，一步到位
在CMakeLists.txt文件中，将find_package(OpenCV REQUIRED)改为find_package(OpenCV 3.2 REQUIRED)，3.2即自己的电脑上opencv3.x的具体版本。

方法二：
将对应3.x版本的旧标志替换为4.x版本的新标志即可，参考如下：

   CV_LOAD_IMAGE_UNCHANGED  = -1 ( = cv::IMREAD_UNCHANGED),
   CV_LOAD_IMAGE_GRAYSCALE  = 0  ( = cv::IMREAD_GRAYSCALE),
   CV_LOAD_IMAGE_COLOR      = 1  ( = cv::IMREAD_COLOR),
   CV_LOAD_IMAGE_ANYDEPTH   = 2  ( = cv::IMREAD_ANYDEPTH),
   CV_LOAD_IMAGE_ANYCOLOR   = 4

   CV_MINMAX = NORM_MINMAX