When you are working with an image, the program records changes that were done, so
you can undo every change you've made by menu command
Edit/ Undo (button ).
You can restore the changes that were undone by menu command
Edit/ Redo (button
).
Note: Program does not store changes in data representation like palette
color, marks that were put, sections, etc... So these operations cannot
be restored by using undo/redo commands.