SECTION 6.4
493
Halftones
NAME
APPEARANCE
DEFINITION
Square
−max
(
|
x
|
,
|
y
|
)
{ abs exch abs 2 copy lt
{ exch }
if
pop neg }
Cross
−min
(
|
x
|
,
|
y
|
)
{ abs exch abs 2 copy gt
{ exch }
if
pop neg }
Rhomboid
0.9
×
x
+
y
--------------------------------
-
2
{ abs exch abs 0.9 mul add 2 div }
Diamond
if
|
x
| + |
y
| ≤
0.75
then
1
−
(x
2
+
y
2
)
else if
|
x
| + |
y
| ≤
1.23
then
1
−
(0.85
×
|
x
| + |
y
| )
else
( |
x
| – 1)
2
+ ( | y | – 1)
2
– 1
{ abs exch abs 2 copy add 0.75 le
{ dup mul exch dup mul add 1 exch sub }
{ 2 copy add 1.23 le
{ 0.85 mul add 1 exch sub }
{ 1 sub dup mul exch 1 sub dup mul add 1 sub }
ifelse }
ifelse }