3.2.4 Using Add, Subtract, and Intersect with the Rectangle and Ellipse Selection Tool Features
As described in Section
3.1.1, the Shift
key can be used to create perfectly square or circular selections, and
the Control key can be used to perform selections centered at the
position of the mouse click. In addition,
3.2 describes how the Shift
key can be used for adding selections, the Control key for subtracting
them, and the Shift and Control keys together for intersecting them.
The question you may be asking, then, is how these features can be
used together. How can a perfect square be subtracted from a prior
selection or a center-initiated ellipse added to one? The answer is
quite simple. The trick is to remember that adding, subtracting, and
intersecting selections is signaled by pressing the Shift key, the
Control key, or both before clicking to initiate the selection.
The sequence for creating a perfectly square or circular selection or
for center-initiated selections is by pressing the Shift key, Control
key, or both after clicking to initiate the selection. These
features can be combined by applying the following steps:
- Begin by pressing the appropriate combination of Shift and
Control to specify whether the selection is to be added to,
subtracted from, or intersected with an already existing selection.
- While the keys are pressed, click and drag in the
image window to initiate the new selection.
- While the left mouse button is pressed, release the Shift
and/or Control keys.
- Apply the appropriate combination of Shift and Control keys to
specify a perfectly square, circular, and/or center-initiated
- While keeping the last combination of Shift and Control keys
pressed, release the mouse button, thus completing the selection.