If you want to crop the image to a given size, e.g., 5.5 x 3.5in, you can use the rectangular select tool to select the part you want and then crop the image using the Image/Crop to Selection command. If you want to scale the image to a given size, you can first crop the image to its contents or whatever you want and then scale it using the Image/Scale image command.
There’s also a crop tool, but I usually use select and then crop. It’s six-of-one, half-a-dozen of the other.
I never print directly from GIMP. I’m sure it works, I just already had my way of doing things, which works well for me. It’s quite simple, reliable and flexible, so you could try it, if you feel like it.
You can export the image as EPS (Encapsulated PostScript) using the “File/Export as …” command.
I use TeX (plain TeX, not LaTeX) together with the DVIPS package to include graphics.
This is the code for a simple TeX file that includes the image “abc.eps” (text following % are comments):
\input epsf
\special{papersize=6in, 4in} % Command for the PostScript interpreter: width by height.
% The same thing, this time for TeX. The dimensions in the two commands must match up!
\hsize=6in
\vsize=4in
% Get rid of the predefined margins and skips:
\advance\voffset by -1in
\advance\hoffset by -1in
\parindent=0pt
\parskip=0pt
\topskip=0pt
\def\epsfsize#1#2{#1} %% Set things up so that images are include at their normal sizes in both dimensions.
% Include the graphic and place it on the page:
\vbox{\vskip1cm % Top margin 1cm
\hbox{\hskip1cm % Left margin 1cm
\epsffile{abc.eps}% Include the graphic (no space before % to make sure the space isn’t read.
\hss}% Fill up and end the line and don’t issue a warning if it goes over the right edge.
} % End the “vbox” (vertical material)
\vfil % Fill up the rest of the page
\eject % End the page
\bye % Exit
If this code is stored in “abc.tex”, run:
tex abc
dvips -o abc.ps abc.dvi
This generates the PostScript file a.ps. For PDF, run this instead of dvips:
dvipdfmx abc.dvi
In this case, the name for the output file isn’t needed (and abc.pdf will be created).
Please note that this won’t work with pdfTeX. Of course, you could use pdfTeX instead, but then the commands in the TeX file would be different.