User Guide

Chapter 5: Painting And Image Editing
To display the Channels palette:
Choose Image | Show Channels.
Vector objects and text objects do not have color or image channels. However, you can create a
channel mask for any object. If an object has a channel mask, you can place the channel mask in edit
mode, and use the Channels palette to work with the channel mask and create alpha channels. Alpha
channels are stored with an object as long as the object has a channel mask.
Color channels
Images in RGB Color, CMYK Color, and LAB Color mode have separate color channels. A color channel
stores one component of the image; e.g., in CMYK Color mode, the Magenta channel stores the
magenta parts of the image. This channel contains the image that would appear on the magenta plate
if you output color separations.
A paint object’s image mode determines the number of color channels. RGB Color images have Red,
Green, and Blue color channels. CMYK Color images have Cyan, Magenta, Yellow, and Black channels.
LAB Color images have Lightness, A, and B channels.
In the Channels palette, a composite channel appears above the color channels. The composite
channel represents the complete image — the composite of the image’s color channels. The
composite channel is labeled RGB, CMYK, or LAB, depending on the image mode.
Other image modes do not have separate color channels. Images in Black & White, Duotone, Indexed,
and Grayscale mode have a single image channel.
Alpha channels
Alpha channels are channels you can use to store and edit selections in any image. Because alpha
channels are used for image selections, they are also referred to as “selection masks.”
After you make a selection in an image, you can save the selection in an alpha channel. Later, you can
load the channel to make the same selection.
An alpha channel is a grayscale channel that is the same size and resolution as the paint object in
which it is stored. Pixels in alpha channels can range in lightness from 0 (black) to 255 (white). The
lightness levels of pixels in an alpha channel correspond to a range of selection levels.
Black pixels in an alpha channel correspond to masked, or non-selected, pixels in an image. White
pixels correspond to selected pixels. Gray pixels correspond to various levels of selection, with
lighter grays corresponding to greater selection than darker grays.
If you want black pixels to correspond to selected, rather than masked pixels, click Selected
Area in the New Channel or Channel Options dialog box.
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