使用pgk-config --modversion opencv查看opencv版本时，提示以下错误

这是由于没有Pkgconfig文件夹以及opencv.pc文件导致的

cd /usr/local/opencv440/lib
sudo mkdir pkgconfig
cd pkgconfig
sudo touch opencv.pc

sudo vim opencv.pc

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/opencv440
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，在bashrc中添加PKG_CONFIG_PATH

export  PKG_CONFIG_PATH=/usr/local/opencv440/pkgconfig

source ~/.bashrc

 再次查看，有了