I am trying PNGOUT compression for compressing the PNG images but have been unable to find any information regarding that. Is there any way to get PNGOUT working on Ubuntu12.04 through command line
You can install pngout by installing the binary . Currently there isn't any deb file for debian/ubuntu as far as i know
Download the binaries from here and install it.
If you don't know how to install it from binary, check this resource on ubuntu
For other optimisation methods you can check out toy/image_optim