<s>
Color	O
digital	O
images	O
are	O
made	O
of	O
pixels	B-Algorithm
,	O
and	O
pixels	B-Algorithm
are	O
made	O
of	O
combinations	O
of	O
primary	O
colors	O
represented	O
by	O
a	O
series	O
of	O
code	O
.	O
</s>
<s>
For	O
instance	O
,	O
an	O
image	O
from	O
a	O
standard	O
digital	B-Device
camera	I-Device
will	O
have	O
a	O
red	O
,	O
green	O
and	O
blue	O
channel	O
.	O
</s>
<s>
In	O
geographic	B-Application
information	I-Application
systems	I-Application
,	O
channels	O
are	O
often	O
referred	O
to	O
as	O
raster	O
bands	O
.	O
</s>
<s>
Another	O
closely	O
related	O
concept	O
is	O
feature	O
maps	O
,	O
which	O
are	O
used	O
in	O
convolutional	B-Architecture
neural	I-Architecture
networks	I-Architecture
.	O
</s>
<s>
For	O
instance	O
,	O
GIF	O
images	O
actually	O
refer	O
to	O
the	O
color	O
in	O
each	O
pixel	B-Algorithm
by	O
an	O
index	B-Data_Structure
number	I-Data_Structure
,	O
which	O
refers	O
to	O
a	O
table	O
where	O
three	O
color	O
components	O
are	O
stored	O
.	O
</s>
<s>
However	O
,	O
regardless	O
of	O
how	O
a	O
specific	O
format	O
stores	O
the	O
images	O
,	O
discrete	O
color	B-Algorithm
channels	I-Algorithm
can	O
always	O
be	O
determined	O
,	O
as	O
long	O
as	O
a	O
final	O
color	O
image	O
can	O
be	O
rendered	O
.	O
</s>
<s>
The	O
concept	O
of	O
channels	O
is	O
extended	O
beyond	O
the	O
visible	O
spectrum	O
in	O
multispectral	O
and	O
hyperspectral	B-Application
imaging	I-Application
.	O
</s>
<s>
RGB	O
channels	O
roughly	O
follow	O
the	O
color	O
receptors	O
in	O
the	O
human	O
eye	O
,	O
and	O
are	O
used	O
in	O
computer	B-Device
displays	I-Device
and	O
image	B-Application
scanners	I-Application
.	O
</s>
<s>
If	O
the	O
RGB	O
image	O
is	O
24-bit	O
(	O
the	O
industry	O
standard	O
as	O
of	O
2005	O
)	O
,	O
each	O
channel	O
has	O
8	O
bits	O
,	O
for	O
red	O
,	O
green	O
,	O
and	O
blue	O
—	O
in	O
other	O
words	O
,	O
the	O
image	O
is	O
composed	O
of	O
three	O
images	O
(	O
one	O
for	O
each	O
channel	O
)	O
,	O
where	O
each	O
image	O
can	O
store	O
discrete	O
pixels	B-Algorithm
with	O
conventional	O
brightness	O
intensities	O
between	O
0	O
and	O
255	O
.	O
</s>
<s>
If	O
the	O
RGB	O
image	O
is	O
48-bit	O
(	O
very	O
high	O
color-depth	O
)	O
,	O
each	O
channel	O
has	O
16-bit	O
per	O
pixel	B-Algorithm
color	O
,	O
that	O
is	O
16-bit	O
red	O
,	O
green	O
,	O
and	O
blue	O
for	O
each	O
per	O
pixel	B-Algorithm
.	O
</s>
<s>
YUV	O
images	O
are	O
an	O
affine	B-Algorithm
transformation	I-Algorithm
of	O
the	O
RGB	O
colorspace	O
,	O
originated	O
in	O
broadcasting	O
.	O
</s>
<s>
HSV	O
,	O
or	O
hue	B-Language
saturation	O
value	O
,	O
stores	O
color	O
information	O
in	O
three	O
channels	O
,	O
just	O
like	O
RGB	O
,	O
but	O
one	O
channel	O
is	O
devoted	O
to	O
brightness	O
(	O
value	O
)	O
,	O
and	O
the	O
other	O
two	O
convey	O
colour	O
information	O
.	O
</s>
<s>
HSV	O
is	O
especially	O
useful	O
in	O
lossy	B-Algorithm
video	O
compression	O
,	O
where	O
loss	O
of	O
color	O
information	O
is	O
less	O
noticeable	O
to	O
the	O
human	O
eye	O
.	O
</s>
<s>
The	O
alpha	B-Algorithm
channel	I-Algorithm
stores	O
transparency	O
information	O
—	O
the	O
higher	O
the	O
value	O
,	O
the	O
more	O
opaque	O
that	O
pixel	B-Algorithm
is	O
.	O
</s>
<s>
No	O
camera	O
or	O
scanner	O
measures	O
transparency	O
,	O
although	O
physical	O
objects	O
certainly	O
can	O
possess	O
transparency	O
,	O
but	O
the	O
alpha	B-Algorithm
channel	I-Algorithm
is	O
extremely	O
useful	O
for	O
compositing	O
digital	O
images	O
together	O
.	O
</s>
<s>
The	O
GIF	O
and	O
PNG	O
image	O
formats	O
use	O
alpha	B-Algorithm
channels	I-Algorithm
on	O
the	O
World	O
Wide	O
Web	O
to	O
merge	O
images	O
on	O
web	O
pages	O
so	O
that	O
they	O
appear	O
to	O
have	O
an	O
arbitrary	O
shape	O
even	O
on	O
a	O
non-uniform	O
background	O
.	O
</s>
<s>
In	O
digitizing	O
images	O
,	O
the	O
color	B-Algorithm
channels	I-Algorithm
are	O
converted	O
to	O
numbers	O
.	O
</s>
<s>
Since	O
images	O
contain	O
thousands	O
of	O
pixels	B-Algorithm
,	O
each	O
with	O
multiple	O
channels	O
,	O
channels	O
are	O
usually	O
encoded	O
in	O
as	O
few	O
bits	O
as	O
possible	O
.	O
</s>
<s>
Among	O
other	O
techniques	O
,	O
lossy	B-Algorithm
video	O
compression	O
uses	O
chroma	O
subsampling	O
to	O
reduce	O
the	O
bit	O
depth	O
in	O
color	B-Algorithm
channels	I-Algorithm
(	O
hue	B-Language
and	O
saturation	O
)	O
,	O
while	O
keeping	O
all	O
brightness	O
information	O
(	O
value	O
in	O
HSV	O
)	O
.	O
</s>
