It is possible to go back to an earlier state of an image by selecting the History option under the Edit menu. The "History" dialog lists the states that you can recover. The actual states are shown on the left of the dialog and the operation that corresponds to each of the states is shown on the right.
Use the scroll bar, if necessary, to see more of the states of the image, and then click on the state you would like to recover. You can then proceed to work with the recovered image.
Note that any intermediate states between the current and the recovered state are lost, unless you choose one of them from the "History" dialog. Also there is a limit to the number of previous states remembered in the dialog.
You can use the History palette in conjunction with the Historic Brush (see Historic brush).
The History palette functions in a similar way to the Undo option in the Edit menu. Consequently, the Purge Undo command in the Edit menu empties both the History palette and the Undo store.
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