Compare before/after

Go to the "Preview" heading. There are several icons to use:

Show the whole edited image
While this button is pressed, Photo Mate will show the "before" image
Show the current edits on the left, and the "before" on the right
Show the current edits on the right, and the "before" on the left
Show the current edits on the top, and the "before" on the bottom
Show the current edits on the bottom, and the "before" on the top
Switch the current edits and the "before": All edits you've done will now be stored in the "before" side, and you can do a new edit. Press it again to switch the current edits again with the last stored edits. This allows you to easily compare two seperate edits.