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This chapter is from the book

This chapter is from the book

Saving and Loading Selections

In the previous exercise, you had the opportunity to load a selection that I had made instead of creating it yourself. After making that particular selection (which took only about five minutes), I saved it as part of the Photoshop file. If a selection is not saved as a selection, it is lost as soon as the file is closed—even if the file is saved as a Photoshop PSD file.

The Alpha Channel

So, how do you save a selection? If you invest a lot of time making a selection, you should be able to save it. The process is simple—you use the Alpha channel. Sounds like a science fiction channel on your local cable TV, doesn't it? The Alpha channel actually is not a channel at all, but rather the name assigned for additional channels (in the Channels palette) used as general-purpose storage space in a graphics file. You can rename these channels, of course, but Photoshop will generate the Alpha channels in numerical order. The new channel is still technically referred to as an Alpha channel (or simply a channel) to differentiate it from the image mode channels (such as the Red, Green, and Blue channels found in an RGB document). How many Alpha channels can fit into a Photoshop file? Good question. How big a file can you live with? Adobe allows an image to have up to 24 channels (which includes color and Alpha channels), but be warned that the more channels saved in a file, the higher the overall file size of the document.

Saving a Selection

So let's get back to the original question of saving a selection. You can get the same result a couple of different ways.

One method is to go to the Select menu and choose Save Selection. This opens the Save Selection dialog box, shown as item 1 in Figure 3.15. If the image already has an existing channel, you can add your new selection to the existing one or you can save the selection to a new channel. Choose New and give the channel a descriptive name (as was done for the TuxedoJon image in the previous steps).

The second method is to view the Channels palette and click the Save selection as channel icon at the bottom of the Channels palette (or Alt(Opt)+click to view a dialog box that will allow you to name the channel). An Alpha channel with the selection information is generated (item 2 in the figure). Another way to rename an Alpha channel is to double-click the channel title to select the channel name; then type the new name (similar to renaming layers on the Layers palette).

You must save the image as a Photoshop (.psd) or a TIFF (.tif) file to save the channel information. If you don't save in one of these formats, Photoshop will do you the courtesy of giving you a single obscure warning message that there are some features that will not be saved in the format that you have chosen before you save in that format and lose the channel forever.

Figure 3.15Figure 3.15 The Save Selection dialog box (item 1) or the Channels palette (item 2) will give you access to saving your selection as a channel.

Loading a Selection

When you open the file and want to access the saved selection from the channel, display the Channels palette and Ctrl(„)+click the channel with your selection, or open the Select menu and choose Load Selection. Open and pick the name of the Alpha channel that you or someone else tucked away into the image. This may surprise you, but many stock photography companies offer selections in their photos. Two of these companies are Photospin (http://www.photospin.com), a great online photo subscription service, and Heremera (http://www.hermera.com), which offers large collections of photo objects on CDs (lots and lots of CDs).

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