"resize" is probably the terminology you were looking for. I guess resizing
might be considered compressing photos. I don't know. But Gimp can do this
and comes with the default instalation. Make your copy, then resize each
image. or copy a whole folder of pictures, and resize them all at once from
the command line with imagemagik. look at this page for some commands:

dptnt.com/.../

sudo apt-get instal imagemagickl will download and install the program on
your pc.