Package opencv was not found in the pkg-config search path.opencv.c问题

安装好后opencv后执行下面这条语句的时候出错：
pkg-config --cflags opencv

Package opencv was not found in the pkg-config search path.
Perhaps you should add the directory containing `opencv.pc'
to the PKG_CONFIG_PATH environment variable
No package 'opencv' found

原因： 缺失了opencv.pc这个配置信息文件
解决方法： 创建opencv.pc文件，注意添加的路径

cd /usr/local/lib
ls pkgconfig     // 如果没有该文件夹  进行创建  一般都有
sudo mkdir pkgconfig
cd pkgconfig
sudo touch opencv.pc  // 查看是否有opencv4.pc 有的话复制一下

然后在opencv.pc中添加以下信息，注意这些信息需要与自己安装opencv时的库路径对应：

prefix=/usr/local
exec_prefix=${prefix}
includedir=${prefix}/include
libdir=${exec_prefix}/lib

Name: opencv
Description: The opencv library
Version:4.0.1
Cflags: -I${includedir}/opencv4
Libs: -L${libdir} -lopencv_shape -lopencv_stitching -lopencv_objdetect -lopencv_superres -lopencv_videostab -lopencv_calib3d -lopencv_features2d -lopencv_highgui -lopencv_videoio -lopencv_imgcodecs -lopencv_video -lopencv_photo -lopencv_ml -lopencv_imgproc -lopencv_flann  -lopencv_core

保存退出，然后将文件导入到环境变量：

export  PKG_CONFIG_PATH=/usr/local/lib/pkgconfig

再执行 pkg-config --cflags --libs opencv时输出结果如下：

-I/usr/local/include/opencv4 -L/usr/local/lib \
-lopencv_shape -lopencv_stitching -lopencv_objdetect \
-lopencv_superres -lopencv_videostab -lopencv_calib3d \
 -lopencv_features2d -lopencv_highgui -lopencv_videoio \
 -lopencv_imgcodecs -lopencv_video -lopencv_photo -lopencv_ml \
 -lopencv_imgproc -lopencv_flann -lopencv_core

然后进行 make 如果还是有问题 make之前先make clean 再次尝试 一般都会成功
还是有问题的话 看一下MakeFile 文件 是否添加opencv的头文件和库文件路径