CHAPTER 7
522
Transparency
NAME
RESULT
HardLight
Multiplies or screens the colors, depending on the source color value. The effect is similar
to shining a harsh spotlight on the backdrop.
Multiply
(
c
b
,
2
×
c
s
)
B
(
c
b
,
c
s
)
=
Screen
(
c
b
,
2
×
c
s
1
)
SoftLight
if
c
s
0.5
if
c
s
>
0.5
Darkens or lightens the colors, depending on the source color value. The effect is similar
to shining a diffused spotlight on the backdrop.
c
b
(
1
2
×
c
s
) ×
c
b
× (
1
c
b
)
B
(
c
b
,
c
s
) =
c
b
+
(
2
×
c
s
1
) × (
D
(
c
b
) –
c
b
)
where
if
c
s
0.5
if
c
s
>
0.5
( (
16
×
x
12
) ×
x
+
4
) ×
x
D
(
x
) =
x
Difference
if
x
0.25
if
x
>
0.25
Subtracts the darker of the two constituent colors from the lighter color:
B
(
c
b
,
c
s
) =
c
b
c
s
Painting with white inverts the backdrop color; painting with black produces no change.
Exclusion
Produces an effect similar to that of the
Difference
mode but lower in contrast. Painting
with white inverts the backdrop color; painting with black produces no change.
B
(
c
b
,
c
s
) =
c
b
+
c
s
2
×
c
b
×
c
s
Table 7.3 lists the standard nonseparable blend modes. Since the nonseparable
blend modes consider all color components in combination, their computation
depends on the blending color space in which the components are interpreted.
They may be applied to all multiple-component color spaces that are allowed as
blending color spaces (see Section 7.2.3, “Blending Color Space”).
All of these blend modes conceptually entail the following steps:
1. Convert the backdrop and source colors from the blending color space to an
intermediate
HSL
(hue-saturation-luminosity) representation.
2. Create a new color from some combination of hue, saturation, and luminosity
components selected from the backdrop and source colors.
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