How to install OpenCV on arch linux

Question

I have tried installing opencv on arch using the aur package. It has successfully installed but when I try to import opencv2 in python, I get the following error

ImportError: libhdf5.so.100: cannot open shared object file: No such file or directory

Not just python , even when I tried running a c++ sample code using this, I got the same error. I have tried searching the net, found a few people who faced a similar issue but still I am unable to fix it.

I have installed Open CV version 3.2

Answer 1

There are multiple packages with similar names but only one that works.

If you have not yet installed OpenCV, run:

pacman -S opencv
pacman -S python-opencv

Install hdf5:

pacman -S hdf5

Note that instructions for Sikuli, which depends on OpenCV, indicate that a symbolic link is required in /usr/lib. A system upgrade can break the link, which will have to be recreated to point to the most recent version of the OpenCV Java library:

# ls -la /usr/lib/libopencv_java*
-rwxr-xr-x 1 root root 2225952 Jul 18 02:48 /usr/lib/libopencv_java440.so
lrwxrwxrwx 1 root root      20 Aug  5 22:42 /usr/lib/libopencv_java.so -> libopencv_java440.so

This can be accomplished using the ln command:

sudo su -
cd /usr/lib
rm libopencv_java.so
ln -s libopencv_java440.so libopencv_java.so

Answer 2

In version 4, in the default configuration, compiling opencv requires hdf5 and vtk, however it's not listed as a dependency of opencv.

That is mentioned in the two bugs on archlinux page: 1, 2.

There are 2 possible workarounds:

1. sudo pacman -S hdf5 vtk (takes about 231.24 MiB of memory)
2. If your program don't require hdf5 and vtk, remove -lopencv_hdf and -lopencv_viz from /usr/lib/pkgconfig/opencv4.pc (in case the program use pkg-config), or remove the 2 flags while compiling.

Warning: If you use workaround 2, update of opencv package will revert those changes. You may want to add them as a NoUpgrade entry in pacman.conf (read man page for details), but the file will no longer be updated and something else may break.