User Guide

Using Selections212
Combining Selections
Using Boolean Operations
When you save selections, you can use
Boolean operations (add, subtract,
and intersect) to combine the saved
selection with an existing channel.
Adding a selection combines it with
the existing channel. Subtracting a
selection cuts it out of the existing
channel. When you intersect a
selection, you include only those parts
that are common to the selection and
the existing channel.
For information about specifying
Boolean operations when saving
selections, refer to “To modify an
existing channel:” on page 211.
When you load saved selections, or
channels, you can use Boolean
operations to combine the loaded
channel with the current selection.
Adding a channel combines it with the
current selection. Subtracting a
channel cuts it out of the current
selection. When you intersect a
channel, you include only those parts
that are common to the current
selection and the loaded channel.
For information about specifying
Boolean operations when loading
selections, refer to “To load a selection
from a channel:” on page 211.
There are many practical uses for
loading a selection using Boolean
operations. For example, in the owl
image below, the artist created and
saved selections for each area she
wanted to work with separately—the
eyes, beak, and outline.
To show the selections clearly in the
graphics below, the selections were
saved to channels, reloaded, and
displayed as red overlays. For
information about displaying
channels as colored overlays, refer to
“To view a channel as a colored
overlay:” on page 222.
The owl image.
The following steps are performed to
create a precise “face” selection that
does not include the beak and eyes:
• The eye and beak channels (saved
selections) are loaded and added.
• The combined selection is saved to
the “eyebeak” channel.