Chapter 15: Using Masks and Channels

Overview

In This Chapter

• Using channels and alpha channels

• Duplicating, renaming, and selecting more than one channel

• Saving selections as alpha channels

• Loading a selection into an image

• Reshaping an alpha channel

• Using Quick Mask mode

• Creating layer masks

• Reshaping layer masks

• Creating a text cutout using a layer mask

• Working with clipping masks

Every image you create in Photoshop contains channels. These channels store an image’s color information. The number of channels in an image depends upon the color mode in which the image is set. For instance, an image set in RGB mode has three default channels — a Red channel that stores red information, a Green channel that stores green information, and a Blue channel that stores blue information. If an image has more than one layer, each layer has its own set of channels.

Alpha channels are grayscale channels that you can add to an image. They are used to store selections. Alpha channel selections are used to protect specific areas of an image from editing while changes, such as recoloring, filters, and other effects, are applied to the rest of the unmasked (unselected) image.

Layer masks in Photoshop are like Halloween masks: A Halloween mask covers the face, concealing it; but any cutouts — for eyes or mouth, for instance — leave those areas visible. You put layer masks on top of an image and make “cutouts” to make some areas visible and editable.

Layer masks control how different areas of a layer are revealed. You can use layer masks as test areas for applying special effects without permanently changing an image. If you like the effects and want to make them permanent, you can then apply a mask to an image.

Layer masks and channels can be saved in the Photoshop’s native PSD file format and Photoshop’s enhanced TIF and PDF formats.