Package opencv4 was not found in the pkg-config search path. Perhaps you should add the directory containing `opencv4.pc' code example

Example: 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

export PKG_CONFIG_PATH=/usr/lib/pkgconfig:/usr/lib/arm-linux-gnueabi/pkgconfig