VISION allows to undo the modification done on an image, by undoing successively the effect of the last commands. The number of undo's can be configured in the preferences of the Options menu, up to 99 levels of undo from the last applied operation. The method used allows to memorised the previous operations either in memory or on disk.
The text of the undo item in the Edit menu contains the name of the command that will be undone. For instance, after having drawn a line, the command will be displayed as Undo Line. When working on several windows, the commands to be undone can be relative to different images. If the undo does not corresponds to the current image, VISION warns you and deletes, if the undo is confirmed, the command in the relevant window, even if it is not the active one.
Allows to redo the last command undone. This function has only one level.
Frees the memory used by the undo buffer. This command can be used when a message warns you VISION has not enough memory left to apply an operation, since the undo buffer can use a huge amount of space, either in memory or on disk. Once the undo buffer is free, it is not possible to go back.