embedding linux into a scanner

I'd really appreciate some help with a project I am about to embark
on. I want to build a scanner with an LCD monitor that will hopefully
scan an image and then maybe manipulate it and display it on an
attached LCD monitor.
 
I want to go down the route of installing linux on a small PC board
and to
then attach an interface from the PC board that will link up to
specific hardware parts and control them.
I understand this means I will require a graphics card to display to
the LCD monitor and so on.

My question is what flavour of linux do I go for ? I guess it has to
be minimalist ? I really want the OS to be hidden from the user.
 
Secondly I was wondering how will I install linux so it boots and then
goes straight to the application that will manipulate the scanner ?
 
Thirdly although C is normally used to control hardware I was
wondering if I can manipulate hardware using java's JNI because I
would also like to write the applications that will manipulate the
scanned image in java. Will this be possible or should i use C/ C++
through out.
 
 
Any help would be appreciated,
 
thanks
Paul