<s>
Non-local	B-Algorithm
means	I-Algorithm
is	O
an	O
algorithm	O
in	O
image	B-Algorithm
processing	I-Algorithm
for	O
image	O
denoising	O
.	O
</s>
<s>
Unlike	O
"	O
local	O
mean	O
"	O
filters	O
,	O
which	O
take	O
the	O
mean	O
value	O
of	O
a	O
group	O
of	O
pixels	O
surrounding	O
a	O
target	O
pixel	O
to	O
smooth	O
the	O
image	O
,	O
non-local	B-Algorithm
means	I-Algorithm
filtering	O
takes	O
a	O
mean	O
of	O
all	O
pixels	O
in	O
the	O
image	O
,	O
weighted	O
by	O
how	O
similar	O
these	O
pixels	O
are	O
to	O
the	O
target	O
pixel	O
.	O
</s>
<s>
If	O
compared	O
with	O
other	O
well-known	O
denoising	O
techniques	O
,	O
non-local	B-Algorithm
means	I-Algorithm
adds	O
"	O
method	O
noise	O
"	O
(	O
i.e.	O
</s>
<s>
Recently	O
non-local	B-Algorithm
means	I-Algorithm
has	O
been	O
extended	O
to	O
other	O
image	B-Algorithm
processing	I-Algorithm
applications	O
such	O
as	O
deinterlacing	O
,	O
view	O
interpolation	O
,	O
and	O
depth	O
maps	O
regularization	O
.	O
</s>
<s>
The	O
computational	O
complexity	O
of	O
the	O
non-local	B-Algorithm
means	I-Algorithm
algorithm	O
is	O
quadratic	O
in	O
the	O
number	O
of	O
pixels	O
in	O
the	O
image	O
,	O
making	O
it	O
particularly	O
expensive	O
to	O
apply	O
directly	O
.	O
</s>
<s>
Another	O
approximation	O
uses	O
summed-area	B-Algorithm
tables	I-Algorithm
and	O
fast	O
Fourier	O
transform	O
to	O
calculate	O
the	O
similarity	O
window	O
between	O
two	O
pixels	O
,	O
speeding	O
up	O
the	O
algorithm	O
by	O
a	O
factor	O
of	O
50	O
while	O
preserving	O
comparable	O
quality	O
of	O
the	O
result	O
.	O
</s>
