Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Are you talking about a command line tool like the built-in image (man photo) and third-party ImageMagick / GraphicsMagick or is it a GUI App like Preview or Gimp you're looking for? What filetypes are your source and destination files? Do you need batch processing?
 
Im taking about any format any file that will just take one image file and turn it into two images
You can do it with Preview. Copy one part, create a new document, and paste that part. Then you can either crop the existing image or do the same thing for the second half.
 
Yes I rethought of that the problem is how can I crop the copy after Ive pasted it into a document
Make a selection of what you want to keep, then from the tools menu, select "crop" or Command-K.
 
If you need to "extract" an image from a Pages document, add extension .zip to the filename, double-click it and grab the image from the unzipped folder structure. More comfortable are tools like StuffitDeluxe's Archive Manager, that can browse the document contents directly (Maybe The Archive Browser from Unarchiver site can do this, too).
For the initial question on how to split any file format and output any file format, maybe GraphicConverter by Lemke Software is the best answer. It has a Split function and can read and write a lot of file formats. Though, I think there are plenty of alternatives that can be used for this task, if one narrows down file formats. If Preview works, then just use it.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.