<s>
An	O
image	B-Algorithm
histogram	I-Algorithm
is	O
a	O
type	O
of	O
histogram	B-Algorithm
that	O
acts	O
as	O
a	O
graphical	O
representation	O
of	O
the	O
tonal	O
distribution	O
in	O
a	O
digital	B-Algorithm
image	I-Algorithm
.	O
</s>
<s>
It	O
plots	O
the	O
number	O
of	O
pixels	B-Algorithm
for	O
each	O
tonal	O
value	O
.	O
</s>
<s>
By	O
looking	O
at	O
the	O
histogram	B-Algorithm
for	O
a	O
specific	O
image	O
a	O
viewer	O
will	O
be	O
able	O
to	O
judge	O
the	O
entire	O
tonal	O
distribution	O
at	O
a	O
glance	O
.	O
</s>
<s>
Image	B-Algorithm
histograms	I-Algorithm
are	O
present	O
on	O
many	O
modern	O
services	O
.	O
</s>
<s>
This	O
is	O
less	O
useful	O
when	O
using	O
a	O
raw	B-Application
image	I-Application
format	I-Application
,	O
as	O
the	O
dynamic	O
range	O
of	O
the	O
displayed	O
image	O
may	O
only	O
be	O
an	O
approximation	O
to	O
that	O
in	O
the	O
raw	B-Application
file	I-Application
.	O
</s>
<s>
The	O
horizontal	O
axis	O
of	O
the	O
graph	O
represents	O
the	O
tonal	O
variations	O
,	O
while	O
the	O
vertical	O
axis	O
represents	O
the	O
total	O
number	O
of	O
pixels	B-Algorithm
in	O
that	O
particular	O
tone	O
.	O
</s>
<s>
The	O
vertical	O
axis	O
represents	O
the	O
size	O
of	O
the	O
area	O
(	O
total	O
number	O
of	O
pixels	B-Algorithm
)	O
that	O
is	O
captured	O
in	O
each	O
one	O
of	O
these	O
zones	O
.	O
</s>
<s>
Thus	O
,	O
the	O
histogram	B-Algorithm
for	O
a	O
very	O
dark	O
image	O
will	O
have	O
most	O
of	O
its	O
data	O
points	O
on	O
the	O
left	O
side	O
and	O
center	O
of	O
the	O
graph	O
.	O
</s>
<s>
Conversely	O
,	O
the	O
histogram	B-Algorithm
for	O
a	O
very	O
bright	O
image	O
with	O
few	O
dark	O
areas	O
and/or	O
shadows	O
will	O
have	O
most	O
of	O
its	O
data	O
points	O
on	O
the	O
right	O
side	O
and	O
center	O
of	O
the	O
graph	O
.	O
</s>
<s>
Image	B-Application
editors	I-Application
typically	O
create	O
a	O
histogram	B-Algorithm
of	O
the	O
image	O
being	O
edited	O
.	O
</s>
<s>
The	O
histogram	B-Algorithm
plots	O
the	O
number	O
of	O
pixels	B-Algorithm
in	O
the	O
image	O
(	O
vertical	O
axis	O
)	O
with	O
a	O
particular	O
brightness	O
or	O
tonal	O
value	O
(	O
horizontal	O
axis	O
)	O
.	O
</s>
<s>
Algorithms	O
in	O
the	O
digital	O
editor	O
allow	O
the	O
user	O
to	O
visually	O
adjust	O
the	O
brightness	O
value	O
of	O
each	O
pixel	B-Algorithm
and	O
to	O
dynamically	O
display	O
the	O
results	O
as	O
adjustments	O
are	O
made	O
.	O
</s>
<s>
Histogram	B-Algorithm
equalization	I-Algorithm
is	O
a	O
popular	O
example	O
of	O
these	O
algorithms	O
.	O
</s>
<s>
In	O
the	O
field	O
of	O
computer	B-Application
vision	I-Application
,	O
image	B-Algorithm
histograms	I-Algorithm
can	O
be	O
useful	O
tools	O
for	O
thresholding	B-Algorithm
.	O
</s>
<s>
Because	O
the	O
information	O
contained	O
in	O
the	O
graph	O
is	O
a	O
representation	O
of	O
pixel	B-Algorithm
distribution	O
as	O
a	O
function	O
of	O
tonal	O
variation	O
,	O
image	B-Algorithm
histograms	I-Algorithm
can	O
be	O
analyzed	O
for	O
peaks	O
and/or	O
valleys	O
.	O
</s>
<s>
This	O
threshold	O
value	O
can	O
then	O
be	O
used	O
for	O
edge	B-Algorithm
detection	I-Algorithm
,	O
image	B-Algorithm
segmentation	I-Algorithm
,	O
and	O
co-occurrence	B-Algorithm
matrices	I-Algorithm
.	O
</s>
