<s>
Blend	B-Algorithm
modes	I-Algorithm
(	O
alternatively	O
blending	O
modes	O
or	O
mixing	B-Algorithm
modes	I-Algorithm
)	O
in	O
digital	B-Application
image	I-Application
editing	I-Application
and	O
computer	O
graphics	O
are	O
used	O
to	O
determine	O
how	O
two	O
layers	B-Algorithm
are	O
blended	O
with	O
each	O
other	O
.	O
</s>
<s>
The	O
default	O
blend	B-Algorithm
mode	I-Algorithm
in	O
most	O
applications	O
is	O
simply	O
to	O
obscure	O
the	O
lower	O
layer	O
by	O
covering	O
it	O
with	O
whatever	O
is	O
present	O
in	O
the	O
top	O
layer	O
(	O
see	O
alpha	B-Algorithm
compositing	I-Algorithm
)	O
;	O
because	O
each	O
pixel	B-Algorithm
has	O
numerical	O
values	O
,	O
there	O
also	O
are	O
many	O
other	O
ways	O
to	O
blend	O
two	O
layers	B-Algorithm
.	O
</s>
<s>
Most	O
graphics	B-Application
editing	I-Application
programs	I-Application
,	O
such	O
as	O
Adobe	B-Operating_System
Photoshop	I-Operating_System
and	O
GIMP	B-Application
,	O
allow	O
users	O
to	O
modify	O
the	O
basic	O
blend	B-Algorithm
modes	I-Algorithm
,	O
for	O
example	O
by	O
applying	O
different	O
levels	O
of	O
opacity	O
to	O
the	O
top	O
"	O
layer	O
"	O
.	O
</s>
<s>
This	O
is	O
the	O
standard	O
blend	B-Algorithm
mode	I-Algorithm
which	O
uses	O
the	O
top	O
layer	O
alone	O
,	O
without	O
mixing	O
its	O
colors	O
with	O
the	O
layer	O
beneath	O
it	O
:	O
</s>
<s>
where	O
a	O
is	O
the	O
value	O
of	O
a	O
color	B-Algorithm
channel	I-Algorithm
in	O
the	O
underlying	O
layer	O
,	O
and	O
b	O
is	O
that	O
of	O
the	O
corresponding	O
channel	O
of	O
the	O
upper	O
layer	O
.	O
</s>
<s>
The	O
result	O
is	O
most	O
typically	O
merged	O
into	O
the	O
bottom	O
layer	O
using	O
"	O
simple	O
"	O
(	O
b	O
over	O
a	O
)	O
alpha	B-Algorithm
compositing	I-Algorithm
(	O
making	O
the	O
actual	O
formula	O
)	O
,	O
but	O
other	O
Porter-Duff	B-Algorithm
operations	O
are	O
possible	O
.	O
</s>
<s>
The	O
compositing	O
step	O
results	O
in	O
the	O
top	O
layer	O
's	O
shape	O
,	O
as	O
defined	O
by	O
its	O
alpha	B-Algorithm
channel	I-Algorithm
,	O
appearing	O
over	O
the	O
bottom	O
layer	O
.	O
</s>
<s>
The	O
dissolve	O
mode	O
takes	O
random	O
pixels	B-Algorithm
from	O
both	O
layers	B-Algorithm
.	O
</s>
<s>
With	O
top	O
layer	O
opacity	O
greater	O
than	O
that	O
of	O
the	O
bottom	O
layer	O
,	O
most	O
pixels	B-Algorithm
are	O
taken	O
from	O
the	O
top	O
layer	O
,	O
while	O
with	O
low	O
opacity	O
most	O
pixels	B-Algorithm
are	O
taken	O
from	O
the	O
bottom	O
layer	O
.	O
</s>
<s>
No	O
anti-aliasing	B-Algorithm
is	O
used	O
with	O
this	O
blend	B-Algorithm
mode	I-Algorithm
,	O
so	O
the	O
pictures	O
may	O
look	O
grainy	O
and	O
harsh	O
.	O
</s>
<s>
Adobe	B-Operating_System
Photoshop	I-Operating_System
generates	O
a	O
pseudo-random	O
noise	O
dither	O
pattern	O
on	O
startup	O
,	O
with	O
each	O
pixel	B-Algorithm
location	O
in	O
a	O
2D	O
raster	O
array	O
assigned	O
a	O
gray	O
value	O
(	O
R	O
=	O
G	O
=	O
B	O
)	O
and	O
an	O
alpha	O
value	O
of	O
1	O
(	O
"	O
on	O
"	O
)	O
.	O
</s>
<s>
As	O
the	O
opacity	O
of	O
the	O
top	O
layer	O
is	O
reduced	O
,	O
the	O
alpha	O
value	O
of	O
some	O
of	O
the	O
gray	O
pixels	B-Algorithm
is	O
switched	O
from	O
1	O
to	O
0	O
(	O
"	O
off	O
"	O
)	O
,	O
with	O
the	O
result	O
that	O
image	O
pixels	B-Algorithm
corresponding	O
to	O
a	O
gray-valued	O
pixel	B-Algorithm
in	O
the	O
raster	O
array	O
are	O
either	O
on	O
(	O
visible	O
,	O
opaque	O
)	O
or	O
off	O
(	O
invisible	O
,	O
transparent	O
)	O
,	O
with	O
no	O
opacity	O
gradation	O
.	O
</s>
<s>
Multiply	O
and	O
Screen	O
blend	B-Algorithm
modes	I-Algorithm
are	O
basic	O
blend	B-Algorithm
modes	I-Algorithm
for	O
darkening	O
and	O
lightening	O
images	O
,	O
respectively	O
.	O
</s>
<s>
Multiply	O
blend	B-Algorithm
mode	I-Algorithm
takes	O
the	O
RGB	O
channel	O
values	O
from	O
0	O
to	O
1	O
of	O
each	O
pixel	B-Algorithm
in	O
the	O
top	O
layer	O
and	O
multiples	O
them	O
with	O
the	O
values	O
for	O
the	O
corresponding	O
pixel	B-Algorithm
from	O
the	O
bottom	O
layer	O
.	O
</s>
<s>
This	O
mode	O
is	O
commutative	O
:	O
exchanging	O
two	O
layers	B-Algorithm
does	O
not	O
change	O
the	O
result	O
.	O
</s>
<s>
If	O
the	O
two	O
layers	B-Algorithm
contain	O
the	O
same	O
picture	O
,	O
multiply	O
blend	B-Algorithm
mode	I-Algorithm
is	O
equivalent	O
to	O
a	O
quadratic	O
curve	B-Algorithm
,	O
or	O
gamma	O
correction	O
with	O
γ	O
=	O
2	O
.	O
</s>
<s>
For	O
image	B-Application
editing	I-Application
it	O
is	O
sometimes	O
more	O
convenient	O
to	O
simply	O
go	O
to	O
the	O
Curves	O
dialog	O
of	O
the	O
software	O
,	O
because	O
it	O
gives	O
more	O
flexibility	O
in	O
the	O
shape	O
of	O
the	O
curves	O
.	O
</s>
<s>
If	O
one	O
layer	O
contains	O
a	O
homogeneous	O
color	O
,	O
such	O
as	O
the	O
gray	O
color	O
(	O
0.8	O
,	O
0.8	O
,	O
0.8	O
)	O
,	O
multiply	O
blend	B-Algorithm
mode	I-Algorithm
is	O
equivalent	O
to	O
a	O
curve	B-Algorithm
that	O
is	O
simply	O
a	O
straight	O
line	O
.	O
</s>
<s>
With	O
Screen	O
blend	B-Algorithm
mode	I-Algorithm
,	O
the	O
values	O
of	O
the	O
pixels	B-Algorithm
in	O
the	O
two	O
layers	B-Algorithm
are	O
inverted	O
,	O
multiplied	O
,	O
and	O
then	O
inverted	O
again	O
.	O
</s>
<s>
This	O
mode	O
is	O
commutative	O
:	O
exchanging	O
two	O
layers	B-Algorithm
does	O
not	O
change	O
the	O
result	O
.	O
</s>
<s>
If	O
one	O
layer	O
contains	O
a	O
homogeneous	O
gray	O
,	O
Screen	O
blend	B-Algorithm
mode	I-Algorithm
is	O
equivalent	O
to	O
using	O
this	O
gray	O
value	O
as	O
opacity	O
when	O
doing	O
"	O
normal	O
mode	O
"	O
blend	O
with	O
white	O
top	O
layer	O
.	O
</s>
<s>
Overlay	O
combines	O
Multiply	O
and	O
Screen	O
blend	B-Algorithm
modes	I-Algorithm
.	O
</s>
<s>
An	O
overlay	O
with	O
the	O
same	O
picture	O
looks	O
like	O
an	O
S-curve	O
.	O
</s>
<s>
The	O
inverse	O
relationship	O
between	O
Overlay	O
and	O
Hard	O
Light	O
makes	O
them	O
"	O
commuted	O
blend	B-Algorithm
modes	I-Algorithm
"	O
.	O
</s>
<s>
The	O
Photoshop	B-Operating_System
and	O
illusions.hu	O
flavors	O
also	O
produce	O
the	O
same	O
result	O
when	O
the	O
top	O
layer	O
is	O
pure	O
white	O
(	O
the	O
differences	O
between	O
these	O
two	O
are	O
in	O
how	O
one	O
interpolates	O
between	O
these	O
3	O
results	O
)	O
.	O
</s>
<s>
The	O
formula	O
used	O
by	O
Photoshop	B-Operating_System
as	O
of	O
2012	O
has	O
a	O
discontinuity	O
of	O
local	O
contrast	O
,	O
and	O
other	O
formulas	O
correct	O
it	O
.	O
</s>
<s>
Photoshop	B-Operating_System
's	O
formula	O
is	O
:	O
</s>
<s>
This	O
is	O
a	O
linear	O
interpolation	O
between	O
Multiply	O
(	O
for	O
a	O
=	O
0	O
)	O
and	O
Screen	O
(	O
for	O
a	O
=	O
1	O
)	O
blend	B-Algorithm
modes	I-Algorithm
.	O
</s>
<s>
It	O
can	O
also	O
be	O
seen	O
as	O
a	O
linear	O
interpolation	O
between	O
the	O
gamma	O
correction	O
with	O
γ	O
=	O
2	O
(	O
for	O
b	O
=	O
0	O
)	O
,	O
and	O
a	O
certain	O
tonal	O
curve	B-Algorithm
(	O
for	O
b	O
=	O
1	O
)	O
.	O
</s>
<s>
(	O
The	O
latter	O
curve	B-Algorithm
is	O
equivalent	O
to	O
applying	O
γ	O
=	O
2	O
to	O
the	O
negative	O
of	O
image	O
.	O
)	O
</s>
<s>
The	O
formula	O
specified	O
by	O
recent	O
W3C	O
drafts	O
for	O
SVG	B-Application
and	O
Canvas	B-Language
is	O
mathematically	O
equivalent	O
to	O
the	O
Photoshop	B-Operating_System
formula	O
with	O
a	O
small	O
variation	O
where	O
b≥	O
0.5	O
and	O
a≤	O
0.25	O
:	O
</s>
<s>
This	O
is	O
also	O
the	O
formula	O
used	O
by	O
Cairo	B-Language
,	O
and	O
in	O
earlier	O
PDF	B-Application
documentation	O
.	O
</s>
<s>
But	O
now	O
the	O
image	O
for	O
b	O
=	O
1	O
is	O
not	O
γ	O
=	O
0.5	O
,	O
but	O
the	O
result	O
of	O
a	O
tonal	O
curve	B-Algorithm
which	O
differs	O
from	O
the	O
curve	B-Algorithm
of	O
γ	O
=	O
0.5	O
for	O
small	O
values	O
of	O
a	O
:	O
while	O
gamma	O
correction	O
with	O
γ	O
=	O
0.5	O
may	O
increase	O
the	O
value	O
of	O
a	O
many	O
times	O
,	O
this	O
new	O
curve	B-Algorithm
limits	O
the	O
increase	O
of	O
a	O
by	O
coefficient	O
4	O
.	O
</s>
<s>
The	O
Screen	O
blend	B-Algorithm
mode	I-Algorithm
inverts	O
both	O
layers	B-Algorithm
,	O
multiplies	O
them	O
,	O
and	O
then	O
inverts	O
that	O
result	O
.	O
</s>
<s>
The	O
Color	O
Dodge	O
blend	B-Algorithm
mode	I-Algorithm
divides	O
the	O
bottom	O
layer	O
by	O
the	O
inverted	O
top	O
layer	O
.	O
</s>
<s>
The	O
operation	O
is	O
not	O
invertible	O
due	O
to	O
possible	O
clipping	B-Algorithm
of	O
highlights	O
.	O
</s>
<s>
(	O
The	O
clipping	B-Algorithm
happens	O
in	O
the	O
same	O
area	O
as	O
for	O
the	O
Linear	O
Dodge	O
.	O
)	O
</s>
<s>
The	O
perceived	O
contrast	O
increases	O
when	O
there	O
is	O
no	O
clipping	B-Algorithm
.	O
</s>
<s>
The	O
Linear	O
Dodge	O
blend	B-Algorithm
mode	I-Algorithm
simply	O
sums	O
the	O
values	O
in	O
the	O
two	O
layers	B-Algorithm
(	O
also	O
known	O
as	O
additive	O
blending	O
)	O
.	O
</s>
<s>
When	O
the	O
top	O
layer	O
contains	O
a	O
homogeneous	O
color	O
,	O
this	O
effect	O
is	O
equivalent	O
to	O
changing	O
the	O
output	O
black	B-Algorithm
point	I-Algorithm
to	O
this	O
color	O
,	O
and	O
(	O
input	O
)	O
white	O
point	O
to	O
the	O
inverted	O
color	O
.	O
</s>
<s>
The	O
contrast	O
is	O
decreased	O
when	O
there	O
is	O
no	O
clipping	B-Algorithm
.	O
</s>
<s>
The	O
Multiply	O
mode	O
simply	O
multiplies	O
each	O
component	O
in	O
the	O
two	O
layers	B-Algorithm
.	O
</s>
<s>
When	O
the	O
top	O
layer	O
contains	O
a	O
homogeneous	O
color	O
,	O
this	O
effect	O
is	O
equivalent	O
to	O
changing	O
the	O
black	B-Algorithm
point	I-Algorithm
to	O
the	O
inverted	O
color	O
.	O
</s>
<s>
The	O
operation	O
is	O
not	O
invertible	O
due	O
to	O
possible	O
clipping	B-Algorithm
of	O
shadows	O
.	O
</s>
<s>
The	O
clipping	B-Algorithm
happens	O
in	O
the	O
same	O
area	O
as	O
for	O
the	O
Linear	O
Burn	O
.	O
</s>
<s>
The	O
Linear	O
Burn	O
mode	O
sums	O
the	O
value	O
in	O
the	O
two	O
layers	B-Algorithm
and	O
subtracts	O
1	O
.	O
</s>
<s>
Vivid	O
Light	O
:	O
this	O
blend	B-Algorithm
mode	I-Algorithm
combines	O
Color	O
Dodge	O
and	O
Color	O
Burn	O
(	O
rescaled	O
so	O
that	O
neutral	O
colors	O
become	O
middle	O
gray	O
)	O
.	O
</s>
<s>
When	O
the	O
top	O
layer	O
's	O
color	O
is	O
lighter	O
than	O
this	O
,	O
this	O
effectively	O
moves	O
the	O
white	O
point	O
of	O
the	O
bottom	O
layer	O
down	O
by	O
twice	O
the	O
difference	O
;	O
when	O
it	O
is	O
darker	O
,	O
the	O
black	B-Algorithm
point	I-Algorithm
is	O
moved	O
up	O
by	O
twice	O
the	O
difference	O
.	O
</s>
<s>
Linear	O
Light	O
:	O
this	O
blend	B-Algorithm
mode	I-Algorithm
combines	O
Linear	O
Dodge	O
and	O
Linear	O
Burn	O
(	O
rescaled	O
so	O
that	O
neutral	O
colors	O
become	O
middle	O
gray	O
)	O
.	O
</s>
<s>
Subtract	O
:	O
this	O
blend	B-Algorithm
mode	I-Algorithm
sums	O
the	O
value	O
in	O
the	O
two	O
layers	B-Algorithm
and	O
subtracts	O
1	O
.	O
</s>
<s>
This	O
blend	O
simply	O
divides	O
pixel	B-Algorithm
values	O
of	O
one	O
layer	O
with	O
the	O
other	O
,	O
but	O
it	O
's	O
useful	O
for	O
brightening	O
photos	O
if	O
the	O
color	O
is	O
on	O
grey	O
or	O
less	O
.	O
</s>
<s>
This	O
blend	B-Algorithm
mode	I-Algorithm
simply	O
adds	O
pixel	B-Algorithm
values	O
of	O
one	O
layer	O
with	O
the	O
other	O
.	O
</s>
<s>
This	O
blend	B-Algorithm
mode	I-Algorithm
simply	O
subtracts	O
pixel	B-Algorithm
values	O
of	O
one	O
layer	O
with	O
the	O
other	O
.	O
</s>
<s>
In	O
some	O
applications	O
such	O
as	O
Krita	B-Application
,	O
"	O
Inverse	O
Subtract	O
"	O
is	O
also	O
available	O
.	O
</s>
<s>
Exclusion	O
is	O
a	O
very	O
similar	O
blend	B-Algorithm
mode	I-Algorithm
with	O
lower	O
contrast	O
.	O
</s>
<s>
Darken	O
Only	O
creates	O
a	O
pixel	B-Algorithm
that	O
retains	O
the	O
smallest	O
components	O
of	O
the	O
foreground	O
and	O
background	O
pixels	B-Algorithm
.	O
</s>
<s>
If	O
the	O
foreground	O
pixel	B-Algorithm
has	O
the	O
components	O
,	O
and	O
the	O
background	O
has	O
,	O
the	O
resultant	O
pixel	B-Algorithm
is	O
:	O
</s>
<s>
It	O
selects	O
the	O
maximum	O
of	O
each	O
component	O
from	O
the	O
foreground	O
and	O
background	O
pixels	B-Algorithm
.	O
</s>
<s>
A	O
few	O
applications	O
,	O
such	O
as	O
Aviary	B-Application
's	I-Application
Peacock	O
and	O
KDE	B-Application
's	O
Krita	B-Application
,	O
supply	O
boolean	O
arithmetic	O
blend	B-Algorithm
modes	I-Algorithm
.	O
</s>
<s>
These	O
combine	O
the	O
binary	O
expansion	O
of	O
the	O
hexadecimal	O
color	O
at	O
each	O
pixel	B-Algorithm
of	O
two	O
layers	B-Algorithm
using	O
boolean	O
logic	O
gates	O
.	O
</s>
<s>
Photoshop	B-Operating_System
's	O
hue	O
,	O
saturation	O
,	O
color	O
,	O
and	O
luminosity	O
blend	B-Algorithm
modes	I-Algorithm
are	O
based	O
on	O
a	O
color	O
space	O
with	O
hue	O
,	O
chroma	O
and	O
luma	O
dimensions	O
.	O
</s>
<s>
Unlike	O
all	O
of	O
the	O
previous	O
blend	B-Algorithm
modes	I-Algorithm
described	O
,	O
which	O
operate	O
on	O
each	O
image	O
channel	O
independently	O
,	O
in	O
each	O
of	O
these	O
modes	O
,	O
some	O
dimensions	O
are	O
taken	O
from	O
the	O
bottom	O
layer	O
,	O
while	O
the	O
remainder	O
are	O
taken	O
from	O
the	O
top	O
layer	O
.	O
</s>
<s>
This	O
makes	O
the	O
operations	O
uninvertible	O
–	O
after	O
a	O
top	O
layer	O
has	O
been	O
applied	O
in	O
one	O
of	O
these	O
blend	B-Algorithm
modes	I-Algorithm
,	O
it	O
is	O
in	O
some	O
cases	O
impossible	O
to	O
restore	O
the	O
appearance	O
of	O
the	O
original	O
(	O
bottom	O
)	O
layer	O
,	O
even	O
by	O
applying	O
a	O
copy	O
of	O
the	O
bottom	O
layer	O
in	O
the	O
same	O
blend	B-Algorithm
mode	I-Algorithm
above	O
both	O
.	O
</s>
<s>
The	O
Hue	O
blend	B-Algorithm
mode	I-Algorithm
preserves	O
the	O
luma	O
and	O
chroma	O
of	O
the	O
bottom	O
layer	O
,	O
while	O
adopting	O
the	O
hue	O
of	O
the	O
top	O
layer	O
.	O
</s>
<s>
The	O
Saturation	O
blend	B-Algorithm
mode	I-Algorithm
preserves	O
the	O
luma	O
and	O
hue	O
of	O
the	O
bottom	O
layer	O
,	O
while	O
adopting	O
the	O
chroma	O
of	O
the	O
top	O
layer	O
.	O
</s>
<s>
The	O
Color	O
blend	B-Algorithm
mode	I-Algorithm
preserves	O
the	O
luma	O
of	O
the	O
bottom	O
layer	O
,	O
while	O
adopting	O
the	O
hue	O
and	O
chroma	O
of	O
the	O
top	O
layer	O
.	O
</s>
<s>
The	O
Luminosity	O
blend	B-Algorithm
mode	I-Algorithm
preserves	O
the	O
hue	O
and	O
chroma	O
of	O
the	O
bottom	O
layer	O
,	O
while	O
adopting	O
the	O
luma	O
of	O
the	O
top	O
layer	O
.	O
</s>
<s>
Because	O
these	O
blend	B-Algorithm
modes	I-Algorithm
are	O
based	O
on	O
a	O
color	O
space	O
which	O
is	O
much	O
closer	O
than	O
RGB	O
to	O
perceptually	O
relevant	O
dimensions	O
,	O
it	O
can	O
be	O
used	O
to	O
correct	B-Algorithm
the	I-Algorithm
color	I-Algorithm
of	O
an	O
image	O
without	O
altering	O
perceived	O
lightness	O
,	O
and	O
to	O
manipulate	O
lightness	O
contrast	O
without	O
changing	O
the	O
hue	O
or	O
chroma	O
.	O
</s>
<s>
The	O
Luminosity	O
mode	O
is	O
commonly	O
used	O
for	O
image	B-Algorithm
sharpening	I-Algorithm
,	O
because	O
human	O
vision	O
is	O
much	O
more	O
sensitive	O
to	O
fine-scale	O
lightness	O
contrast	O
than	O
color	O
contrast	O
.	O
</s>
<s>
Few	O
editors	O
other	O
than	O
Photoshop	B-Operating_System
implement	O
this	O
same	O
color	O
space	O
for	O
their	O
analogs	O
of	O
these	O
blend	B-Algorithm
modes	I-Algorithm
.	O
</s>
<s>
Instead	O
,	O
they	O
typically	O
base	O
their	O
blend	B-Algorithm
modes	I-Algorithm
on	O
HSV	O
(	O
aka	O
HSB	O
)	O
or	O
HSL	O
.	O
</s>
<s>
Blend	B-Algorithm
modes	I-Algorithm
based	O
on	O
HSV	O
are	O
typically	O
labeled	O
hue	O
,	O
saturation	O
,	O
and	O
brightness	O
.	O
</s>
<s>
Using	O
HSL	O
or	O
HSV	O
has	O
the	O
advantage	O
that	O
most	O
operations	O
become	O
invertible	O
(	O
at	O
least	O
in	O
theory	O
)	O
,	O
but	O
the	O
disadvantage	O
that	O
the	O
dimensions	O
of	O
HSL	O
and	O
HSV	O
are	O
not	O
as	O
perceptually	O
relevant	O
as	O
the	O
dimensions	O
of	O
the	O
space	O
Photoshop	B-Operating_System
uses	O
.	O
</s>
<s>
The	O
result	O
of	O
applying	O
several	O
of	O
these	O
modes	O
depends	O
linearly	O
on	O
the	O
pixel	B-Algorithm
level	O
of	O
the	O
top	O
layer	O
.	O
</s>
<s>
Apply	O
two	O
transformations	O
to	O
the	O
bottom	O
layers	B-Algorithm
;	O
</s>
<s>
Many	O
image	B-Application
manipulation	I-Application
programs	O
do	O
not	O
allow	O
such	O
masks	O
;	O
for	O
them	O
this	O
equivalence	O
holds	O
only	O
for	O
grayscale	O
top	O
layers	B-Algorithm
.	O
)	O
</s>
<s>
Some	O
applications	O
allow	O
the	O
user	O
to	O
apply	O
blending	O
modes	O
to	O
painting	O
tools	O
,	O
such	O
as	O
the	O
Brush	O
tool	O
in	O
Photoshop	B-Operating_System
or	O
any	O
painting	O
tools	O
in	O
GIMP	B-Application
.	O
</s>
<s>
When	O
blending	O
modes	O
are	O
used	O
with	O
these	O
tools	O
,	O
the	O
result	O
is	O
calculated	O
based	O
on	O
pixels	B-Algorithm
already	O
existing	O
on	O
the	O
target	O
layer	O
.	O
</s>
<s>
If	O
no	O
pixels	B-Algorithm
currently	O
exist	O
,	O
then	O
the	O
'	O
painted	O
 '	O
pixels	B-Algorithm
are	O
created	O
as	O
if	O
in	O
Normal	O
blending	O
mode	O
.	O
</s>
<s>
A	O
key	O
difference	O
with	O
tool	O
blending	O
versus	O
layer	O
blending	O
is	O
that	O
the	O
results	O
of	O
tool	O
blends	O
are	O
generally	O
not	O
able	O
to	O
be	O
adjusted	O
after	O
the	O
stroke	O
is	O
made	O
,	O
with	O
the	O
exception	O
of	O
stepping	O
backward	O
with	O
the	O
application	O
's	O
Undo	O
command	O
;	O
layer	O
blends	O
may	O
be	O
adjusted	O
with	O
opacity	O
or	O
even	O
switched	O
,	O
as	O
they	O
are	O
applied	O
dynamically	O
between	O
layers	B-Algorithm
.	O
</s>
<s>
Put	O
differently	O
,	O
painting	O
tools	O
alter	O
the	O
pixels	B-Algorithm
on	O
a	O
layer	O
;	O
blend	B-Algorithm
modes	I-Algorithm
applied	O
to	O
two	O
layers	B-Algorithm
do	O
n't	O
alter	O
any	O
pixels	B-Algorithm
,	O
but	O
only	O
affect	O
the	O
resulting	O
visual	O
image	O
.	O
</s>
