You can’t batch process it, because you haven’t grabbed the screenshots yet. Here’s the smallest number of steps you can do to grab screenshots manually.
(This example uses Macromedia Fireworks)
I suggest, setting the background on your desktop to flourescent green, (assuming any icons will be blocked or not seen), then make the window (whatever you’ll be taking the screenshot of) as small as possible before you take the screenshot. Then hit print screen on your keyboard, go to Fireworks, hit CTRL+N, (the size will be set correctly already), hit enter, then hit CTRL+V, then hit ‘W’ on the keyboard. Use that tool to select your desktop background (the green) and hit delete. Then hit CTRL+ALT+T and it should auto trim to the size of the screen shot.
This will be the smallest image to start with. (You should save a copy of this as your large image) From there you can resize using, CTRL+SHIFT+T (opens numeric transform) select resize from the drop down box, then type 713 in the width box. If constrain proportion is checked (the default) then you can hit ENTER or OK, and it should be the right size now.
Then hit CTRL+SHIFT+X to Export the image to your desired format.
If you’re doing a lot, it might be better to get the screen shots, then batch process the changes Contact Me if you’d like to discuss it further or Request an Article Topic.