<s>
In	O
image	B-Algorithm
processing	I-Algorithm
,	O
normalization	B-Algorithm
is	O
a	O
process	O
that	O
changes	O
the	O
range	O
of	O
pixel	B-Algorithm
intensity	O
values	O
.	O
</s>
<s>
Normalization	B-Algorithm
is	O
sometimes	O
called	O
contrast	B-Algorithm
stretching	I-Algorithm
or	O
histogram	B-Algorithm
stretching	O
.	O
</s>
<s>
In	O
more	O
general	O
fields	O
of	O
data	O
processing	O
,	O
such	O
as	O
digital	B-General_Concept
signal	I-General_Concept
processing	I-General_Concept
,	O
it	O
is	O
referred	O
to	O
as	O
dynamic	O
range	O
expansion	O
.	O
</s>
<s>
The	O
purpose	O
of	O
dynamic	O
range	O
expansion	O
in	O
the	O
various	O
applications	O
is	O
usually	O
to	O
bring	O
the	O
image	O
,	O
or	O
other	O
type	O
of	O
signal	O
,	O
into	O
a	O
range	O
that	O
is	O
more	O
familiar	O
or	O
normal	O
to	O
the	O
senses	O
,	O
hence	O
the	O
term	O
normalization	B-Algorithm
.	O
</s>
<s>
For	O
example	O
,	O
if	O
the	O
intensity	O
range	O
of	O
the	O
image	O
is	O
50	O
to	O
180	O
and	O
the	O
desired	O
range	O
is	O
0	O
to	O
255	O
the	O
process	O
entails	O
subtracting	O
50	O
from	O
each	O
of	O
pixel	B-Algorithm
intensity	O
,	O
making	O
the	O
range	O
0	O
to	O
130	O
.	O
</s>
<s>
Then	O
each	O
pixel	B-Algorithm
intensity	O
is	O
multiplied	O
by	O
255/130	O
,	O
making	O
the	O
range	O
0	O
to	O
255	O
.	O
</s>
<s>
Normalization	B-Algorithm
might	O
also	O
be	O
non	O
linear	O
,	O
this	O
happens	O
when	O
there	O
is	O
n't	O
a	O
linear	O
relationship	O
between	O
and	O
.	O
</s>
<s>
Auto-normalization	O
in	O
image	B-Algorithm
processing	I-Algorithm
software	O
typically	O
normalizes	O
to	O
the	O
full	O
dynamic	O
range	O
of	O
the	O
number	O
system	O
specified	O
in	O
the	O
image	O
file	O
format	O
.	O
</s>
