Full sized pics showed according to monitor width

[forester]

Sorry if discussed previously, but my search didn't find anything useful.

I have some really big images in my CPG (over 2048 x 1536) and I've turned off the middle size pictures in order to safe disk space.
I wondered if it's possible not to show the image in full width but to "lock" it according to monitor width (if bigger than monitor's width only)
I know this can be achieved with middle sizing the images, but due to space lack I can't afford it. And I need to keep users' images original resolution.
So what I need is to load full sized pic, but show it 'locked' to users' monitors resolution.

thank to all answers in advance!

[nickfzx]

the highslide plugin for cpg does just this

...do a search for highslide...it enables you to zoom from the thumbnail to the fullsize pic...which is restrained by the browser window size and there is a button in the bottom right corner if you want to see it actual size.