
Alpha Channels 539
A channel — before and after inversion.
In addition, you can introduce interesting effects by filling a channel with a pattern,
gradient, or weave. For more information, see “Working with color fills” on page 229.
To paint in a channel
1 In the Channels panel, display and select the channel you want to work with.
If you want to paint only on a specific area of the channel, make a selection.
2 Choose the Brush tool from the toolbox.
3 Click the Brush Selector on the Brush Selector bar.
4 In the Brush library panel, click a brush category, and brush variant.
The Pen and Airbrush brush categories make good choices.
5 In the Color panel, choose one of the following:
• Black — adds to the protected area
• White — removes from the protected area
• Grey — applies a semi-protected area
When you paint in the channel, hue is irrelevant. The channel carries 8 bits of
information and you need only set a level in that range. The value scale is between
black and white.
6 Paint in the document window.
7 In the Channels panel, click the eye icon next to the RGB channel’s thumbnail
to display the channel in grayscale.
You can also
Control the brush opacity Adjust the Opacity slider on the property
bar.
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