[Cin] zscale's tonemapping on input

[Andrea paz]

I have done many attempts, but always with the same error:

ERROR: zimg >= 2.7.0 not found using pkg-config

In Arch, the zimg package files are as follows:

/usr/include/zimg++.hpp
/usr/include/zimg.h

/usr/lib/libzimg.so
/usr/lib/libzimg.so.2
/usr/lib/libzimg.so.2.0.0
/usr/lib/pkgconfig/zimg.pc

One question: what is “pkg-config”? A CinGG's script? A system script?
I search this:
https://people.freedesktop.org/~dbn/pkg-config-guide.html

He seems to see the library:
sudo pkg-config --list-all zimg | grep zimg
zimg                           zimg - Scaling, colorspace conversion,
and dithering library


sudo pkg-config --simulate zimg
node 'virtual:world' {
    dependency 'zimg';
};
node 'zimg' {
    version = '3.0.5';

I suppose pkg-config can't see the *.pc file in
/usr/lib/pkgconfig/zimg.pc, and I tried editing
/usr/lib/pkgconfig/zimg.pc by putting in:

libdir=${exec_prefix}/lib/pkgconfig

But I keep getting the same error. Any advice?