Installed babl, but gimp2.7 still says No package 'babl' found

I asked this question minutes ago. I am trying to install babl for gimp2.7 using this guide However after I sudo make install babl and ./configure gimp, I still get the following error.

No package 'babl' found

Consider adjusting the PKG_CONFIG_PATH environment variable if you
installed software in a non-standard prefix.

Alternatively, you may set the environment variables BABL_CFLAGS
and BABL_LIBS to avoid the need to call pkg-config.
See the pkg-config man page for more details.

I installed babl with the prefix /opt/gimp-2.7 as in the guide

On using locate, I get

    locate babl
/usr/lib/babl-0.0
/usr/lib/libbabl-0.0.so.0
/usr/lib/libbabl-0.0.so.0.22.0
/usr/lib/babl-0.0/CIE-Lab.so
/usr/lib/babl-0.0/gegl-fixups.so
/usr/lib/babl-0.0/gggl-lies.so
/usr/lib/babl-0.0/gggl.so
/usr/lib/babl-0.0/gimp-8bit.so
/usr/lib/babl-0.0/naive-CMYK.so
/usr/lib/babl-0.0/sse-fixups.so
/usr/share/doc/libbabl-0.0-0
/usr/share/doc/libbabl-0.0-0/AUTHORS
/usr/share/doc/libbabl-0.0-0/NEWS.gz
/usr/share/doc/libbabl-0.0-0/README.gz
/usr/share/doc/libbabl-0.0-0/TODO
/usr/share/doc/libbabl-0.0-0/TODO.Debian
/usr/share/doc/libbabl-0.0-0/changelog.Debian.gz
/usr/share/doc/libbabl-0.0-0/copyright
/var/cache/apt/archives/libbabl-0.0-0_0.0.22-1build1_i386.deb
/var/lib/dpkg/info/libbabl-0.0-0.list
/var/lib/dpkg/info/libbabl-0.0-0.md5sums
/var/lib/dpkg/info/libbabl-0.0-0.postinst
/var/lib/dpkg/info/libbabl-0.0-0.postrm
/var/lib/dpkg/info/libbabl-0.0-0.shlibs

My $Path

/opt/gimp-2.7/bin:/opt/gimp-2.7/bin:/home/abc/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/opt/real/RealPlayer:/babl:/usr/lib

(I added the /babl and /usr/lib)

Where is the fault? Is babl not installed properly? If yes, How do I rectify it? Is the path improper? Where should a 'package' be installed to be findable?

It looks like you need to adjust your PKG_CONFIG_PATH environment variable so the configure script can properly resolve the location of the babl library that you installed in the previous step.

You can do so in two ways:

export PKG_CONFIG_PATH="$PKG_CONFIG_PATH:/opt/gimp-2.7/lib/pkgconfig/"

which will take the current value of PKG_CONFIG_PATH and append /opt/gimp-2.7/lib/pkgconfig/ to it.

When using export the value of PKG_CONFIG_PATH variable will persist during single terminal session. Once the command above is run you can invoke configure script as normal:

./configure --prefix=/opt/gimp-2.7

Another way to achieve the same end result would be to invoke the configure script as below:

PKG_CONFIG_PATH="$PKG_CONFIG_PATH:/opt/gimp-2.7/lib/pkgconfig/" ./configure --prefix=/opt/gimp-2.7

When invoked in this way the value of the PKG_CONFIG_PATH will only be modified for the time of execution of the configure script.