CHAPTER 16 THE IMPORTANCE OF LAYERS AND MASKS 249Other Uses for Paths
Paths have other uses. Although making selections is the most useful task photogra-
phers can do with paths, paths can be filled directly with a color from the palette.
Paths can also be turned into a colored line of variable width.
Paths are so versatile because they are not based on pixels—they are vector objects.
Vector objects are a class of computer graphics unrelated to pixels. Pixels are
arranged in rows and columns, whereas vector objectsare mathematical descriptions
of the location of points and the lines connecting them. Of course, you don’t see the
mathematical equations; only the lines created by the equations are visible on the
monitor. These equations create curved lines, which are called Bezier curves.
Because a Bezier curve is only a set of numbers,
it takes less memory and disk storage than a
memory-hungry bitmap. This means that an
image file composed of a picture plus a set of
paths will be smaller than the same picture plus
saved bitmapped selections. (Selections are saved
as alpha channels.)
If you’d like to experiment with Bezier curves
and the power of paths, follow these steps for
creating a path around an image.- Open an image, preferably one with a
sharp, distinct object that you can trace
with the Pen tool. This exercise will trace a round object so that you can see
how Bezier curves are formed with the Pen tool. - Click to create the first anchor point and hold down the mouse button while
dragging the cursor in the direction you want the curve to go. Two odd-look-
ing direction lines will appear (see Figure 16.13).
FIGURE 16.12
Making a selec-
tion using the
Pen tool.
tip
If you need to outline a
number of items in an
image, use paths instead of
selections. Paths take much
less disk space than alpha
channels, which is where
selections are stored.