Masks let you isolate and protect parts of an image. When you create a mask based on a selection, the area not selected is masked or protected from editing. With masks, you can create and save time-consuming selections and then use them again. In addition, you can use masks for other complex editing tasks—for example, to apply color changes or filter effects to an image.
In Adobe Photoshop, you can make temporary masks, called quick masks, or you can create permanent masks and store them as special grayscale channels, called alpha channels. Photoshop also uses channels to store an image's color information and information about spot color. Unlike layers, channels do not print. You use the Channels palette to view and work with alpha channels. ImageReady does not support channels, except for alpha channels used for PNG transparency and weighted optimization.
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