The History Palette

Choose Window History to view the History palette, as shown in Figure 3-1. The History palette records each significant operation and adds it to a list. Things that don't inherently make a change in your image ” like adjusting settings, changing preferences, or selecting a new foreground color ” don't get added to the list. The oldest operations appear at the top of the list with the most recent operations at the bottom.

image from book
Figure 3-1: The History palette records each significant event as an independent state. To return to a state, just click on it.

Each item in the list is called a state , representing the current condition of your image at a specific moment in time. Each state is named according to the tool, command, or operation used to arrive at that state. The icon next to the name helps to identify the state further. Of course, the best way to find out what a state is like is to click it. Photoshop instantaneously returns you to that state so that you can inspect it in detail. To move forward again, and thus redo all the operations you just undid in one fell swoop, press Ctrl+Z ( z -Z on the Mac) or choose Edit Undo State Change. Or simply click back on the state you were on before you decided to hop back in time in the first place.

That one action ” clicking on a state ” is all you need to know to travel forward and backward through time in Photoshop. If that's all you ever learn, you'll find yourself working with greater speed, freedom, and security than is possible in virtually any other graphics application. The History palette's other capabilities include:

  • Changing the number of states visible on the History palette: By default, Photoshop records the last 20 operations in the History palette. When you perform the 21st operation, the first state falls off the top of the list. To change this behavior, choose Edit (Photoshop on a Mac) Preferences General, or press Ctrl+K ( z -K on the Mac). In the Preferences dialog box, enter your number of states you'd prefer to see listed in the History States option box. The History palette can hold up to 1,000 states. Realize that the more states you want to see, the more RAM Photoshop is going to use. So, mind your resources wisely. If you've got 1GB of RAM or better, go wild. If you've got less than 256MB, don't.

  • Undone states: When you revert to a state by clicking on it, every subsequent state turns gray to show that it's been undone. You can redo a grayed state simply by clicking on it. Of course, if you step back in time, and then perform a new operation, you've followed a different path into the future. All those grayed states are replaced by that new operation, and you have only one opportunity to bring them back ” by pressing Ctrl+Z ( z -Z). Now, if you perform yet another new operation, you've really committed yourself to this new future, and all those old states are gone for good. For an exception to this behavior, see the very next paragraph.

  • Working with non-linear states: Don't like the idea of losing your undone states? Choose the History Options command in the palette menu and select the Allow Non-Linear History check box, shown in Figure 3-2. With this option in place, undone states no longer drop off the list when you perform a new operation. They remain available on the (off) chance that you might want to revisit them. It's like having multiple possible time lines. Trekkies eat this stuff up.

    image from book
    Figure 3-2: Selecting Allow Non-Linear History from the History Options dialog box permits Photoshop to keep states that you have undone.

    Note  

    The Allow Non-Linear History check box does not permit you to undo a single state without affecting the subsequent states. For example, say that you painted with the airbrush, smeared with the Smudge tool, and then cloned with the Clone stamp. You can revert back to that first airbrush state and then apply other operations without losing the option of restoring the state with the smudge and clone. But, you can't hop to the smudge state, undo it, and leave the clone intact as if you'd only applied the airbrush and the clone. In other words, operations can only occur in the sequence they were applied.

  • Stepping through states: As we mentioned earlier, you can press Ctrl+Alt+Z ( z -Option-Z) to undo the active step, or Ctrl+Shift+Z ( z -Shift-Z) to redo the next step in the list. Back stepping goes up the list of states in the History palette; forward stepping goes down. So bear in mind that if the Allow Non- Linear History check box is active, back stepping may take you to a state that was previously inactive.

  • Flying through states: Drag the right-pointing active state marker (see the last state, in blue, in Figure 3-1) up and down the list to rewind and fast-forward, respectively, through time. If the screen image doesn't appear to change as you fly by certain states, it most likely means those states involve small brushstrokes or changes to selection outlines. Otherwise, the changes are quite apparent.

  • Taking a snapshot: Every once in a while, a state comes along that's so great, you don't want it to fall by the wayside 20-plus operations from now. To set a state aside, choose New Snapshot from the palette menu or click the little camera icon at the bottom of the History palette. To rename a snapshot after you create it, just double-click its name at the top of the History palette and enter a new one; or you can name a snapshot as you create it by pressing the Alt key (or Option on the Mac), clicking the camera icon, and entering a name in the resulting dialog box.

    Photoshop lets you store as many snapshots as your computer's RAM permits. Also worth noting, the program automatically creates a snapshot of the image as it appears when the image is first opened. If you don't like this opening snapshot, you can change this behavior by turning off Automatically Create First Snapshot inside the History Options dialog box.

  • Creating a snapshot upon saving the image: Select the Automatically Create New Snapshot When Saving check box in the History Options dialog box to create a new snapshot every time you save your image. This option is useful if you find yourself venturing down uncertain roads from one save to the next and want the ability to back step not only to the last saved state (which you can do by choosing File Revert), but the one before that and the one before that.

  • Saving the state permanently: Snapshots, like everything else in the History palette, last only as long as the current session. If you quit Photoshop or if the program crashes, you lose the entire history list, snapshots included. To save a state so you can refer to it several days from now, choose the New Document command or click the leftmost icon at the bottom of the History palette. You can also drag and drop a state onto the icon. Either way, Photoshop duplicates the state to a new image window. Then you can save the state to the format of your choice.

  • Setting the source for the History brush: Click to the left of a state to identify it as the source state . The History brush icon appears where you click. The source state affects the performance of the History brush, Art History brush, and the Fill command. It also affects the Eraser, if you select Erase to History. The keystroke Ctrl+Alt+Backspace ( z -Option-Delete on the Mac) fills a selection with the source state.

  • Trashing states: If your machine is equipped with little RAM or you're working on a particularly large image, Photoshop may slow down as the states accumulate. If it gets too slow, you may want to purge the History palette. To delete any state as well as those before it, drag the state to the trash icon at the bottom of the palette. Your image updates accordingly . If the Allow Non-Linear History check box is on, clicking the trash can deletes just the active state.

    Tip  

    To clear all states from the History palette, choose the Clear History command from the palette menu. This doesn't immediately empty the RAM, just in case you change your mind and decide you want to undo. After you perform another operation, only then does Photoshop purge the memory for real. If you want the memory emptied right away ” and you're positive that you have no desire whatsoever to undo ” press the Alt key (Option on the Mac) and choose the Clear History command. And if you're really hankering to purge, choose Edit Purge Histories ” this gets rid of all states for all open documents.

    Cross-Reference  

    Layer comps can take certain properties of layers and freeze them in time, in essence allowing you to revert back to a previous state. Although layer comps aren't anywhere near as omniscient as the History palette, they do have the bonus of being saved permanently within the document, so you can still view them weeks, months, or years later. You'll take a close look at layer comps in Chapter 5. But getting back to history, the History Log preference in the General panel of the Preferences dialog box lets you keep written track of the edits you've made to an image. You can't revisit or undo any of those edits, but the log is a handy way of recording an image's history. You can explore this feature in more detail in Chapter 13.



Photoshop CS2 Bible
Photoshop CS2 Bible
ISBN: 0764589725
EAN: 2147483647
Year: 2003
Pages: 95

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