ptg IN THIS CHAPTER Choosing History panel options . . . .175 Changing history states . . . . . . . . . .177 Deleting and clearing history states .178 Using snapshots . . . . . . . . . . . . . . .179 Creating documents from states . . . .181 Using the History Brush tool . . . . . .182 Filling an area with a history state or snapshot . . . . . . . . . . . . . . . .184 10 Using the History panel, you can selec- tively undo or restore previous stages (called “states”) of the current work session. In this chapter, you will choose default set- tings for the History panel; restore, delete, and clear history states; preserve states by using snapshots; create a new document from a state or snapshot; and restore areas of an image to a prior state by using the History Brush tool or by lling a selection or layer with a history state. Choosing History panel options e History panel displays a list of states (edits) that you have made to the currently open document. e most recent state is listed at the bottom. When you click a prior state, the document is restored to that stage of the editing process. What happens to the panel when you do this depends on whether it’s in linear or nonlinear mode, A so you need to learn how the two modes dier. Continued on the following page history Current history state and history state slider C r e a t e N e w D o c u m e n t from Current State C r e a t e N e w Snapshot D e l e t e Current State A i s H i s t o r y p a n e l i s i n l i n e a r m o d e . W h e n w e c l i c k e d an earlier state, the subsequent states became dimmed. S o u r c e f o r the History Brush tool ptg 176 Chapter 10 Choosing a mode for the History panel To choose a mode for the panel, choose History Options from the panel menu, then in the History Options dialog, check or uncheck Allow Non- Linear History. We recommend keeping the History panel in linear mode (unchecking the Allow Non-Linear History option), especially if you’re new to Photoshop. A With the panel in this mode, if you click an earlier state and resume image editing from that state or delete it, all the subsequent (dimmed) states are discarded. is way, the document can be restored to an earlier state with a nice, clean break. In nonlinear mode, if you click on or delete an earlier state, subsequent states aren’t deleted or dimmed. If you resume image editing when an earlier state is selected, your next edit will show up as the latest state on the panel, and all the states in between will be preserved. at is, the latest state will incorporate the earlier stage of the image plus your newest edit. If you change your mind, you can click any in-between state whenever you like and resume editing from there. B Nonlinear is the more exible of the two modes, but it can be confusing or disorienting. B i s H i s t o r y p a n e l i s i n n o n l i n e a r m o d e . W h e n we clicked an earlier state, all the states remained available, even those listed below the one we clicked. A In the History Options dialog, uncheck Allow Non-Linear History for linear mode, or check it for nonlinear mode. Choosing other options for the History panel e last option in the History Options dialog, Make Layer Visibility Changes Undoable, controls whether clicking the visibility icon on the Layers panel is listed as a state on the History panel. We prefer to keep this option o. (For other options in this dialog, see page 179.) To specify the number of states that can be listed on the panel at a time, go to Edit/Photoshop > Preferences (Ctrl-K/Cmd-K) > Performance and, under History & Cache, enter a History States value (the default value is 20). If the maximum number of history states is exceeded during an editing session, the oldest steps are removed to make room for new ones. e maximum number of states may be limited by various factors, includ- ing the image size, the kind of edits made to the image, and currently available system memory. Each open document has its own list of states. Note: Regardless of the preference setting, when you close a document, all history states (and all snapshots) are deleted from the panel! ptg History 177 Changing history states To summarize the two modes for the History panel, if the panel is in linear mode (the Allow Non-Linear History option is o) and you click an earlier state, all the states below the one you click will become dimmed. If you then delete the state you clicked or continue editing the image with that earlier state still selected, all the dimmed states are deleted. (If you change your mind, you can choose Undo imme- diately to restore the deleted states.) If the panel is in nonlinear mode and you click an earlier state, then perform another edit, the new edit will become the latest state, but the prior states won’t be deleted. To change history states: 1. Perform some edits on an image. 2. Do any of the following: Click a state on the History panel. A On the left side of the panel, drag the History State slider upward or downward to the desired state. To Step Forward one state, press Ctrl-Shift-Z/ Cmd-Shift-Z; or to Step Backward one state, press Ctrl-Alt-Z/Cmd-Option-Z. ➤ When you choose File > Revert, it becomes a state on the History panel, and like other states, all the states preceding it are preserved. You can restore the image to a state prior to or after the Revert state. A i s i s a f t e r w e c l i c k e d a p r i o r s t a t e , w i t h t h e History panel in linear mode. ptg 178 Chapter 10 Deleting and clearing history states We will presume you followed our advice and put your History panel in linear mode (you unchecked the Allow Non-Linear History option). With the panel in linear mode, if you delete a state and then resume editing your document, that state and all the subsequent ones will be discarded from the panel. To delete a history state: Do one of the following: Right-click a state on the History panel, choose Delete from the context menu, A then click Yes in the alert dialog. B To bypass the alert, drag the state to be deleted over the Delete Current State button on the History panel. To delete previous states sequentially without an alert appearing, click a state, then Alt-click/ Option-click the Delete Current State button as many times as needed. Note: e Undo command will restore only the last deleted state. To clear the History panel: To clear all states (but not snapshots) from your History panel for all the currently open docu- ments to free up memory, choose Edit > Purge > Histories, then click OK in the alert dialog. is command cannot be undone! To clear all states (but not snapshots) from the History panel for just the current document, right-click any state and choose Clear History. i s c o m m a n d d o e s n ’ t f r e e u p m e m o r y f o r Photoshop, but it can be undone. A Right-click a state and choose Delete from the context menu, then click Yes in the alert dialog. B Because our History panel was in linear mode (Allow Non-Linear History was unchecked) when we deleted a state, all subsequent states were also deleted. ptg History 179 Using snapshots States are deleted from the History panel if any of the following occur: the specied maximum number of history states is exceeded; you clear or purge the panel; or the panel is in linear mode, you click an earlier state, and then resume editing the document. A snapshot, which is created from a history state, remains on the panel even if any of the above occur. When you click a snapshot, the document is restored to the state it represents. Both snapshots and history states are deleted when you close your document. In these instructions, you’ll choose snapshot options, which aect all Photoshop les; on the next page, you’ll learn how to create snapshots for a specic document. To choose snapshot options: 1. Choose History Options from the History panel menu. e History Options dialog opens. A 2. Check or uncheck any of the following options that pertain to snapshots: Automatically Create First Snapshot to have Photoshop create a snapshot every time a le is opened (this option is checked by default and we keep it on). Auto matically Create New Snapshot When Saving to have Photoshop create a snapshot every time a le is saved. e snapshot will be named by the time of day it was created. Show New Snapshot Dialog by Default to have the New Snapshot dialog appear whenever you click the New Snapshot button, enabling you to choose options. 3. Click OK. A e H i s t o r y O p t i o n s d i a l o g c o n t a i n s t h r e e s n a p s h o t o p t i o n s . ptg 180 Chapter 10 If the Automatically Create New Snapshot When Saving option is turned o for your History panel, you should get in the habit of creating snapshots periodically as you work and before running any actions on your document. If you use the New Snapshot dialog (the second method below), you’ll be able to choose whether the snapshot is made from all the layers in the document, from all the layers at a particular state, or from just the current layer. To create a snapshot of a state: Method 1 (without choosing options) 1. Edit your document so it contains the changes that you want to capture as a snapshot. 2. If the Show New Snapshot Dialog by Default option is o in the History Options dialog, click the New Snapshot button. If that option is on, Alt-click/Option-click the New Snapshot button. A new snapshot thumbnail appears below the last one, in the upper section of the panel. Method 2 (choosing options) 1. On the History panel, right-click the state that you want to create a snapshot of and choose New Snapshot. A e layer associated with that history state becomes selected and the New Snapshot dialog opens. B 2. Type a Name for the snapshot. 3. Choose an option from the From menu: Full Document to include in the snapshot all the layers the document contained at the chosen state. Merged Layers to merge into the Background all the layers that were visible at the chosen state. Current Layer to create a snapshot of the layer that became selected when you right-clicked a history state. 4. Click OK. C ➤ To rename a snapshot, double-click the existing name. A Right-click a state and choose New Snapshot from the context menu. B In the New Snapshot dialog, enter a name and choose which part of the image you want the snapshot to be created from. C A thumbnail for the new snapshot appears on the History panel. . Snapshot to have Photoshop create a snapshot every time a le is opened (this option is checked by default and we keep it on). Auto matically Create New Snapshot When Saving to have Photoshop create. page 179.) To specify the number of states that can be listed on the panel at a time, go to Edit /Photoshop > Preferences (Ctrl-K/Cmd-K) > Performance and, under History & Cache, enter. state and choose Clear History. i s c o m m a n d d o e s n ’ t f r e e u p m e m o r y f o r Photoshop, but it can be undone. A Right-click a state and choose Delete from the context menu,