CHAPTER 7
544
Transparency
7.3.7 Summary of Group Compositing Computations
The following restatement of the group compositing formulas also takes isolated
groups and knockout groups into account. See Tables 7.7 and 7.8 on pages 534
and 536 for the meanings of the variables.
〈
C
,
f
,
α
〉
=
Composite
(
C
0
,
α
0
,
G
)
•
Initialization:
f
g
=
α
g
=
0
0
0
α
0
=
0
if the group is isolated
•
For each group element
E
i
∈
G (i
=
1, … ,
n):
⎧
0
b
=
⎨
⎩
i
–
1
if the group is knockout
otherwise
if
E
i
is a group
otherwise
⎧
Composite
(
C
b
,
α
b
,
E
i
)
〈
C
s
,
f
j
,
α
j
〉
=
⎨
i
i
i
⎩
intrinsic color, shape, and
(
shape
×
opacity
)
of
E
i
f
s
=
f
j
×
f
m
×
f
k
i
i
i
i
α
s
=
α
j
× (
f
m
×
q
m
) × (
f
k
×
q
k
)
i
i
i
i
i
i
f
g
=
Union
(
f
g
,
f
s
)
i
i
–
1
i
α
g
=
(
1
–
f
s
) ×
α
g
+
(
f
s
–
α
s
) ×
α
g
+
α
s
i
i
i
–
1
i
i
b
i
α
i
=
Union
(
α
0
,
α
g
)
i
C
t
=
(
f
s
–
α
s
) ×
α
b
×
C
b
+
α
s
× ( (
1
–
α
b
) ×
C
s
+
α
b
×
B
i
(
C
b
,
C
s
)
)
i
i
i
i
i
(
1
–
f
s
) ×
α
i
–
1
×
C
i
–
1
+
C
t
i
C
i
= -----------------------------------------------------------------------
-
α
i