Via Alpha Channel or Selection

Layer masks and selections have one thing in common: They both store their information as grayscale images in alpha channels. This commonality makes it easy to create a layer mask from a selection or a selection from a layer mask. It also opens up the possibility of modifying a grayscale layer mask by working directly on the alpha channel or, alternatively, loading the mask as a selection, altering the selection with selection tools or selection transform commands (or both), and refilling with black or white.

To work on the alpha channel, Alt+Shift-click (Windows), Opt+Shift-click (Mac OS) the layer mask thumbnail. You should see the masked areas take on a rubylith color and the foreground and background colors reset to default, ready for you to paint with black (to expand mask) and white (to contract mask). You can also add a selection and fill with black or white. Use the same shortcut to go back to the composite channel view.

To load the mask as a selection, Ctrl-click (Windows), ^-click (Mac OS) the layer mask thumbnail. Modify the selection (Select^ Transform Selection). Fill the modified selection with black or white and then deselect (Select ^ Deselect).

CROSS-REFERENCE

selections.

See Chapter 9 for more information on working with

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