SECTION 4.4
229
Path Construction and Painting
Two more operators,
v
and
y
, each specify one of the two control points implic-
itly (see Figure 4.9). In both of these cases, one control point and the final point
of the curve are supplied as operands; the other control point is implied:
•
For the
v
operator, the first control point coincides with initial point of the
curve.
•
For the
y
operator, the second control point coincides with final point of the
curve.
(x
2
,
y
2
)
(x
1
,
y
1
)
(x
3
,
y
3
)
(x
3
,
y
3
)
Current point
x
2
y
2
x
3
y
3
v
Current point
x
1
y
1
x
3
y
3
y
FIGURE 4.9
Cubic Bézier curves generated by the
v
and
y
operators
4.4.2 Path-Painting Operators
The path-painting operators end a path object, causing it to be painted on the
current page in the manner that the operator specifies. The principal path-
painting operators are
S
(for
stroking)
and
f
(for
filling).
Variants of these opera-
tors combine stroking and filling in a single operation or apply different rules for
determining the area to be filled. Table 4.10 lists all the path-painting operators.