When Things Go WorngIt's 11 PM on the night before your big presentation. You've been working on this image for thirteen hours, and you're beginning to experience a bad case of "pixel vision." After making a selection, you run a filter, look carefully, and decide that you don't like the effect. But before you can reach Undo, you accidentally click on the document window, deselecting the area.That's not so bad, is it? Not until you realize that undoing will only undo the deselection, not the filter... and that you haven't saved for half an hour. The mistake remains, and there's no way to get rid of it without losing the last 30 minutes of brain-draining work. Or is there? In this section of the chapter, we take a look at the various ways you can save yourself when something goes terribly wrong. UndoThe first defense against any offensive mistake is, of course, Undo. You can find this on the Edit menu, but we suggest keeping one hand conveniently on the Command and Z keys, ready and waiting for the blunder that is sure to come sooner or later. Note that Photoshop is smart enough not to consider some things "undoable." Taking a snapshot, for instance, doesn't count; so you can take a snapshot and then undo whatever you did just before the snapshot. Similarly, you can open the Histogram, hide edges, change foreground or background colors, zoom, scroll, or even duplicate the file, and Photoshop still lets you go back and undo the previous action. Revert to SavedYou'd think this command is pretty easy to interpret. If you've really messed up something in your image, the best option is often simply to revert the entire file to the last saved version by selecting Revert from the File menu. In Photoshop CS, Revert occasionally caused us trouble because it ignored anything we'd done in the Missing Profile or Profile Mismatch dialog boxesit reverted to the file that opened in Photoshop, not the one saved to disk. Photoshop CS2 punts on the whole issue by making Revert unavailable if you make changes in either of these dialog boxes. The History PaletteThere is a school of thought that dictates, "Don't give people what they want, give them what they need." The Photoshop engineering team appears to advocate thisthey spend hours listening to and thinking about what people ask for, then they come back with a feature that goes far beyond what anyone had even thought to request. For example, people long asked Adobe for multiple Undos (the ability to sequentially undo steps that you've taken while editing a Photoshop image). The result is the History palette, which goes far beyond a simple Undo mechanism into a whole new paradigm of working in Photoshop.The History palette, at its most basic, remembers what you've done to your file and lets you either retrace your steps or revert back to any earlier version of the image. Every time you do something to your imagepaint a brush stroke, run a filter, make a selection, and so onPhotoshop saves this change as a state in the History palette (see Figure 2-35). At any time, you can revert the entire image to any previous state, orusing the History Brush tool or the Fill command, which we'll discuss in a momentselectively paint back in time. Figure 2-35. The History palette[View full size image] SnapshotsThe History palette lets you save any number of snapshotsrepresenting a moment in time for your imageso that at any time you can go back to a specific state. There are two main differences between snapshots and states.Photoshop records almost everything you do to an image as a state. By default, snapshots are only recorded when you first open an image and when you click the New Snapshot button in the History palette.When the number of states recorded on the History palette exceeds the Maximum Remembered States value (set in the History Options dialog box), the oldest states start dropping off the list. Snapshots don't disappear until you close the document. Tip: What's in the SnapshotWhen you click the New Snapshot button on the History palette (or select New Snapshot from the palette's flyout menu), Photoshop saves the whole document (individual layers and all). Depending on how many layers you have and how large your document is, this might require a lot of scratch space. If you Option-click the button, Photoshop offers two other less-storage-intensive snapshot choices: a version of the image with merged layers, or just of the currently selected layer. (If you find yourself Option-clicking the button a lot in order to get these options, then turn on the Show New Snapshot Dialog By Default checkbox in History Options. That way, you don't have to press the Option key anymore.) Stepping through statesAs we mentioned earlier, Photoshop saves every brush stroke, every selection, every any thing you do to your image as a state on the History palette (though the state only remains on the palette until you reach the maximum number of states or you close the document). There are three ways to move among states of your image.To revert your image back to a state, you can click on any state's tile in the History palette.You can move the active state marker to a different state on the History palette.You can press Command-Z to step back to the last state (just as you've always been able to do). But you can also press Command-Option-Z to move backward one state at a time, and Command-Shift-Z to move forward one state at a time. In general, when you move to an earlier state, Photoshop grays out every subsequent state on the History palette, indicating that if you do anything now these grayed-out states will be erased. This is like going back to a fork in the road and choosing the opposite path from what you took before. Photoshop offers another option: if you turn on the Allow Non-Linear History checkbox in the History Options dialog box, Photoshop doesn't gray out or remove subsequent states when you move back in time (though it still deletes old states when you hit the maximum number of states limit).Non-Linear History is like returning to the fork in the road, taking the opposite path, but then having the option to return to any state from the first path. For example, you could run a Gaussian Blur on your image using three different amountsreturning the image to the pre-blurred state in the History palette each timeand then switch among these three states to decide which one you wanted to use.The primary problem with Non-Linear History is that it may confuse you more than help you, especially when you're dealing with a number of different "forks in the road." The History BrushReturning to a previous state returns the entire image to that state. But Photoshop's History feature lets you selectively return portions of your image to a previous state, too, with the History Brush and the Fill command. Before painting with the History Brush, first select the source state in the History palette (click in the column to the left of the state from which you want to paint). For instance, let's say you sharpen a picture of a face with Unsharp Masking (see Chapter 9, Sharpness, Detail, and Noise Reduction) and find that the lips have become oversharp. You can select the History Brush, set the source state to the presharpened state, and brush around the lips (though you'd probably want to reduce the opacity of the History Brush to 20 or 30 percent by pressing 2 or 3 first).The History Brush tool (press Y) is very similar to the Eraser tool when the Erase to History checkbox is turned on in the Options bar, but the History Brush lets you paint with modes, such as Multiply and Screen. We used to prefer the History Brush over Erase to History or Fill from History, because they didn't work on high-bit files, but that limitation has disappeared in Photoshop CS2, so now we use whichever gets the job done most easily.Tip: Snap Before ActionIf you run an action in the Actions palette that has more steps than your History States preference, you won't be able to "undo" the action. That's why before running the action you should either save a snapshot of your full document or set the source state for the History Brush to the current state. The latter works because Photoshop never "rolls off" the source state in the History palette, so you don't have to worry about its getting deleted after reaching the maximum number of states. Fill with HistoryOne last nifty technique that can rescue you from a catastrophic "oops" is the Fill command on the Edit menu (press Shift-F5). This lets you fill any selection (or the entire image, if nothing is selected) with the pixels from the current source state on the History palette. We usually use this in preference to the History Brush or Eraser tools when the area to be reverted is easily selectable. Sometimes when we paint with those tools, we overlook some pixels (it's hard to use a brush to paint every pixel in an area at 100 percent). This is never a problem when you use the Fill command.You've always been able to press Option-Delete to fill a selection or layer with the foreground color. In version 4, Photoshop added the ability to automatically preserve transparency on the layer when you add the Shift key (slightly faster than having to turn on the Preserve Transparency checkbox in the Layers palette). Similarly, you can fill with the background color by pressing Command-Delete (add the Shift key to preserve transparency). To fill the layer or selection with the current history source state, press Command-Option-Delete. And, of course, you can add the Shift key to this to fill with Preserve Transparency turned on. |