Adobe Photoshop CS5 One-on-One

So rather than approaching an image in terms
of its sunflowers or other objects, you have
to approach its pixels. This means specifying
which pixels you want to affect and which you
do not using selections.

Isolating an Image Element

Let’s say you want to change the color of the
umbrella shown in Figure 3-2. The umbrella is
so obviously an independent object that even
an infant could pick it out. But Photoshop is
no infant. If you want to select the umbrella,
you must tell Photoshop exactly which group
of pixels you want to modify.

Fortunately, Photoshop provides a wealth of
selection functions to help you do exactly that.
Some functions select entire regions of colors;
others automatically detect and trace edges.
Still others, like the tools I used to describe the
bluish regions in Figure 3-3, select geometric
regions. And if none of those tools does what
you need it to, you can whip out the big guns
and painstakingly define a selection by hand,
one meticulous point at a time. These tools can
all be used together to forge the perfect outline,
one that exactly describes the perimeter of the
element or area that you want to select.

As if to make up for its inability to immediately
perceive image elements such as umbrellas and
sunflowers, Photoshop treats selection outlines—
those dotted lines that mark the borders of a
selection—as independent objects. You can
move, scale, or rotate selection outlines inde-
pendently of an image. You can combine them
or subtract from them. You can undo and redo
selection modifications. You can even save se-
lection outlines for later use (as you’ll see later
in Lesson 10).

Figure 3-2.

Figure 3-3.

Selected umbrella

Colorized using Gradient Map

Isolating an Image Element 65