STEPS: Transferring a Selection to an Independent Channel

1. Convert the selection to a mask channel. One way to do this is to choose Select ^ Save Selection (or right-click in the image window and choose Save Selection from the pop-up menu), which saves the selection as a mask. The dialog box shown in Figure 9-27 appears, asking you where you want to put the mask. In most cases, you'll want to save the mask to a separate channel inside the current image. To do so, make sure that the name of the current image appears in the Document pop-up menu. Then select New from the Channel pop-up menu, enter any name for the channel that you like, and press Enter.

Make selection Make channel Delete channel New channel

Figure 9-27: The Save Selection dialog box enables you to convert your selection outline to a mask and save it to a new or existing channel.

Make selection Make channel Delete channel New channel

Figure 9-27: The Save Selection dialog box enables you to convert your selection outline to a mask and save it to a new or existing channel.

If you have an old channel you want to replace, select the channel's name from the Channel pop-up menu. The radio buttons at the bottom of the dialog box become available, permitting you to add the mask to the channel, subtract it, or intersect it. These radio buttons work like the equivalent options that appear when you make a path into a selection outline (as discussed in the previous chapter), but they blend the masks together, instead. The result is the same as if you were adding, subtracting, or intersecting selection outlines, except it's expressed as a mask.

Alternatively, you can save the mask to a new multichannel document all its own. To do this, choose New from the Document pop up menu and press Enter.

Tip Man, what a lot of options! If you only want to save the selection to a new chan nel and be done with it, you needn't bother with the Save Selection command or dialog box. Just click the make channel icon at the bottom of the Channels palette (labeled in Figure 9-27). Photoshop automatically creates a new channel, converts the selection to a mask, and places the mask in the channel.

Regardless of which of these many methods you choose, your selection outline remains intact.

2. View the mask in the Channels palette. To do so, click the appropriate channel name in the Channels palette — automatically named Alpha 1 unless you assigned a name of your own. In Figure 9-27, I replaced the contents of a channel called Existing Mask, so this is where my mask now resides.

This step isn't the least bit mandatory. It just lets you see your mask and generally familiarize yourself with how masks look. Remember, white represents selection, black is deselected, and gray is partial selection.

Tip If you didn't name your mask in Step 1 and you want to name it now, double click the Alpha 1 item in the Channels palette and enter a name in the result ing dialog box.

3. Return to the standard image-editing mode by clicking on the first channel name in the Channels palette. Better yet, press Ctrl+1 if you're editing a grayscale image or Ctrl+tilde (~) if the image is in color.

4. Save the image to disk to store the selection permanently as part of the file.

A handful of formats — PICT, Pixar, PNG, TIFF, Targa, and native Photoshop — accommodate RGB images with an extra mask channel. But only the TIFF and native Photoshop format can handle more than four channels, both saving up to 24 channels in all. I generally use the TIFF format with LZW compression when saving images with masks. Because TIFF supports layers in Photoshop 6, you aren't restricted to the Photoshop format for multilayered images with masks. (See Chapter 3 for more on that exciting news.)

Both the native Photoshop format and TIFF can compress masks so that they take up substantially less room on disk. The Photoshop format does this automatically. When saving a TIFF image, be sure to turn on the LZW Compression check box. In both cases, this run-line compression is entirely safe. It does not change a single pixel in the image; it merely writes the code in a more efficient manner.

Tip If you performed the steps in the "Creating gradient arrows" section earlier in this chapter, you know that you can also save a quick mask to its own channel for later * use. But in case you missed those steps, or you're saving them for a special occasion, here's how it works. When you enter the quick mask mode, the Channels palette displays an item called Quick Mask. The italic letters show the channel is temporary and will not be saved with the image. (To clone it to a permanent channel, drag the Quick Mask item onto the page icon at the bottom of the Channels palette). Now save the image to the TIFF or Photoshop format, and you're backed up.

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Photoshop Secrets

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