Ubuntu安装OpenCV时Could not find a package configuration file provided by “OpenCV“

安装opencv过程省略，具体可查找其他博主的教程。
在catkin_make时，出现以下错误：

CMake Error at /opt/ros/melodic/share/catkin/cmake/catkinConfig.cmake:83 (find_package):
  Could not find a package configuration file provided by "OpenCV" with any
  of the following names:

    OpenCVConfig.cmake
    opencv-config.cmake

  Add the installation prefix of "OpenCV" to CMAKE_PREFIX_PATH or set
  "OpenCV_DIR" to a directory containing one of the above files.  If "OpenCV"
  provides a separate development package or SDK, be sure it has been
  installed.
Call Stack (most recent call first):
  probot_vision_pick/probot_ocr/CMakeLists.txt:12 (find_package)

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查看error

网上很多都说改CMakeList.txt，然后添加set（…）的路径。
一开始改了我的工作空间的src下的CMakeList.txt，发现不对，其实应该是打开error中显示的路径的CMakeLists.txt

Call Stack (most recent call first):
  probot_vision_pick/probot_ocr/CMakeLists.txt:12 (find_package)
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如图所示：

set(OpenCV_DIR /opt/ros/kinetic/share/OpenCV-3.3.1-dev)
find_package(catkin REQUIRED COMPONENTS
.........省略
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修改成

# set(OpenCV_DIR /opt/ros/kinetic/share/OpenCV-3.3.1-dev)
set(OpenCV_DIR /usr/share/OpenCV)
find_package(catkin REQUIRED COMPONENTS
......省略
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！！！注意，/usr/share/OpenCV，为OpenCVConfig.cmake的路径，可以在终端输入

locate OpenCVConfig.cmake
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得到其所在目录。
保存，重新catkin_make即可。

PS：注意要多看终端的报错，有时第一个error即是问题关键，后边的只是连锁反应而已。