<s>
Image	B-Algorithm
color	B-Algorithm
transfer	I-Algorithm
is	O
a	O
function	O
that	O
maps	O
(	O
transforms	O
)	O
the	O
colors	O
of	O
one	O
(	O
source	O
)	O
image	B-Algorithm
to	O
the	O
colors	O
of	O
another	O
(	O
target	O
)	O
image	B-Algorithm
.	O
</s>
<s>
A	O
color	B-Algorithm
mapping	I-Algorithm
may	O
be	O
referred	O
to	O
as	O
the	O
algorithm	O
that	O
results	O
in	O
the	O
mapping	O
function	O
or	O
the	O
algorithm	O
that	O
transforms	O
the	O
image	B-Algorithm
colors	O
.	O
</s>
<s>
The	O
image	B-Algorithm
modification	O
process	O
is	O
sometimes	O
called	O
color	B-Algorithm
transfer	I-Algorithm
or	O
,	O
when	O
grayscale	O
images	O
are	O
involved	O
,	O
brightness	O
transfer	O
function	O
(	O
BTF	O
)	O
;	O
it	O
may	O
also	O
be	O
called	O
photometric	B-Algorithm
camera	I-Algorithm
calibration	I-Algorithm
or	O
radiometric	O
camera	O
calibration	O
.	O
</s>
<s>
The	O
term	O
image	B-Algorithm
color	B-Algorithm
transfer	I-Algorithm
is	O
a	O
bit	O
of	O
a	O
misnomer	O
since	O
most	O
common	O
algorithms	O
transfer	O
both	O
color	O
and	O
shading	O
.	O
</s>
<s>
(	O
Indeed	O
,	O
the	O
example	O
shown	O
on	O
this	O
page	O
predominantly	O
transfers	O
shading	O
other	O
than	O
a	O
small	O
orange	O
region	O
within	O
the	O
image	B-Algorithm
that	O
is	O
adjusted	O
to	O
yellow	O
.	O
)	O
</s>
<s>
There	O
are	O
two	O
types	O
of	O
image	B-Algorithm
color	B-Algorithm
transfer	I-Algorithm
algorithms	O
:	O
those	O
that	O
employ	O
the	O
statistics	O
of	O
the	O
colors	O
of	O
two	O
images	O
,	O
and	O
those	O
that	O
rely	O
on	O
a	O
given	O
pixel	B-Algorithm
correspondence	O
between	O
the	O
images	O
.	O
</s>
<s>
An	O
example	O
of	O
an	O
algorithm	O
that	O
employs	O
the	O
statistical	O
properties	O
of	O
the	O
images	O
is	O
histogram	B-Algorithm
matching	I-Algorithm
.	O
</s>
<s>
This	O
is	O
a	O
classic	O
algorithm	O
for	O
color	B-Algorithm
transfer	I-Algorithm
,	O
but	O
it	O
can	O
suffer	O
from	O
the	O
problem	O
that	O
it	O
is	O
too	O
precise	O
so	O
that	O
it	O
copies	O
very	O
particular	O
color	O
quirks	O
from	O
the	O
target	O
image	B-Algorithm
,	O
rather	O
than	O
the	O
general	O
color	O
characteristics	O
,	O
giving	O
rise	O
to	O
color	O
artifacts	O
.	O
</s>
<s>
An	O
example	O
of	O
such	O
algorithm	O
is	O
one	O
that	O
adjusts	O
the	O
mean	O
and	O
the	O
standard	B-General_Concept
deviation	I-General_Concept
of	O
each	O
of	O
the	O
source	O
image	B-Algorithm
channels	O
to	O
match	O
those	O
of	O
the	O
corresponding	O
reference	O
image	B-Algorithm
channels	O
.	O
</s>
<s>
A	O
common	O
algorithm	O
for	O
computing	O
the	O
color	B-Algorithm
mapping	I-Algorithm
when	O
the	O
pixel	B-Algorithm
correspondence	O
is	O
given	O
is	O
building	O
the	O
joint-histogram	O
(	O
see	O
also	O
co-occurrence	B-Algorithm
matrix	I-Algorithm
)	O
of	O
the	O
two	O
images	O
and	O
finding	O
the	O
mapping	O
by	O
using	O
dynamic	B-Algorithm
programming	I-Algorithm
based	O
on	O
the	O
joint-histogram	O
values	O
.	O
</s>
<s>
When	O
the	O
pixel	B-Algorithm
correspondence	O
is	O
not	O
given	O
and	O
the	O
image	B-Algorithm
contents	O
are	O
different	O
(	O
due	O
to	O
different	O
point	O
of	O
view	O
)	O
,	O
the	O
statistics	O
of	O
the	O
image	B-Algorithm
corresponding	O
regions	O
can	O
be	O
used	O
as	O
an	O
input	O
to	O
statistics-based	O
algorithms	O
,	O
such	O
as	O
histogram	B-Algorithm
matching	I-Algorithm
.	O
</s>
<s>
The	O
corresponding	O
regions	O
can	O
be	O
found	O
by	O
detecting	O
the	O
corresponding	B-Algorithm
features	I-Algorithm
.	O
</s>
<s>
Color	B-Algorithm
transfer	I-Algorithm
processing	O
can	O
serve	O
two	O
different	O
purposes	O
:	O
one	O
is	O
calibrating	O
the	O
colors	O
of	O
two	O
cameras	O
for	O
further	O
processing	O
using	O
two	O
or	O
more	O
sample	O
images	O
,	O
the	O
second	O
is	O
adjusting	O
the	O
colors	O
of	O
two	O
images	O
for	O
perceptual	O
visual	O
compatibility	O
.	O
</s>
<s>
Color	O
calibration	O
is	O
an	O
important	O
pre-processing	O
task	O
in	O
computer	B-Application
vision	I-Application
applications	O
.	O
</s>
<s>
Examples	O
of	O
such	O
applications	O
are	O
:	O
Image	B-Algorithm
differencing	I-Algorithm
,	O
registration	B-Algorithm
,	O
object	O
recognition	O
,	O
multi-camera	O
tracking	B-Operating_System
,	O
co-segmentation	B-Algorithm
and	O
stereo	B-Algorithm
reconstruction	I-Algorithm
.	O
</s>
<s>
Other	O
applications	O
of	O
image	B-Algorithm
color	B-Algorithm
transfer	I-Algorithm
have	O
been	O
suggested	O
.	O
</s>
<s>
These	O
include	O
the	O
co-option	O
of	O
color	O
palettes	O
from	O
recognised	O
sources	O
such	O
as	O
famous	O
paintings	O
and	O
the	O
use	O
as	O
a	O
further	O
alternative	O
to	O
color	O
modification	O
methods	O
commonly	O
found	O
in	O
commercial	O
image	B-Algorithm
processing	O
applications	O
such	O
as	O
‘	O
posterise’	O
,	O
‘	O
solarise’	O
and	O
‘	O
gradient’	O
.	O
</s>
<s>
However	O
,	O
others	O
such	O
as	O
Xiao	O
and	O
Ma	O
reverse	O
that	O
usage	O
and	O
indeed	O
it	O
seems	O
more	O
natural	O
to	O
consider	O
that	O
the	O
colors	O
from	O
a	O
source	O
image	B-Algorithm
are	O
directed	O
at	O
a	O
target	O
image	B-Algorithm
.	O
</s>
<s>
Adobe	O
use	O
the	O
term	O
source	O
for	O
the	O
color	O
reference	O
image	B-Algorithm
in	O
the	O
Photoshop	O
Match	O
Color	O
function	O
.	O
</s>
<s>
To	O
minimise	O
further	O
confusion	O
,	O
it	O
may	O
be	O
good	O
practice	O
henceforth	O
to	O
utilise	O
terms	O
such	O
as	O
input	O
image	B-Algorithm
or	O
base	O
image	B-Algorithm
and	O
color	O
source	O
image	B-Algorithm
or	O
color	O
palette	O
image	B-Algorithm
respectively	O
.	O
</s>
