Adobe photoshop cs 2.0 User Guide

 Scripting Photoshop CS2     61

In a script, you can access a 

Document

 object’s history states using the 

HistoryStates

 object, which is a 

property of the 

Document

 object. You can use a 

HistoryStates

 object to reset a document to a previous 

state or to fill a 

Selection

 object.

The following examples revert the document contained in the variable 

docRef

 back to the form and 

properties it had when it was first saved. Using history states in this fashion gives you the ability to undo 
modifications to the document.

set current history state of current document to history state 1 ¬

of current document

docRef.ActiveHistoryState = docRef.HistoryStates(0)

docRef.activeHistoryState = docRef.historyStates[0]

Reverting back to a previous history state does not remove any latter states from the history 
collection. Use the 

Purge

 command to remove latter states from the 

History States

 collection as 

shown below:

AS

purge history caches

VBS

appRef.Purge(2) 'for psPurgeTarget --> 2 (psHistoryCaches)

JS

app.purge(PurgeTarget.HISTORYCACHES)

The example below saves the current state, applies a filter, and then reverts back to the saved history state.

set savedState to current history state of current document
filter current document using motion blur with options ¬

{angle:20, radius: 20}

set current history state of current document to savedState

Set savedState = docRef.ActiveHistoryState
docRef.ApplyMotionBlur 20, 20
docRef.ActiveHistoryState = savedState

savedState = docRef.activeHistoryState
docRef.applyMotionBlur( 20, 20 )
docRef.activeHistoryState = savedState

You use the 

Notifier

 object to tie an event to a script. For example, if you would like Photoshop CS2 to 

automatically create a new document when you open the application, you could tie a script that creates a 

Document

 object to an 

Open Application

 event.