<s>
The	O
image	B-General_Concept
fusion	I-General_Concept
process	O
is	O
defined	O
as	O
gathering	O
all	O
the	O
important	O
information	O
from	O
multiple	O
images	O
,	O
and	O
their	O
inclusion	O
into	O
fewer	O
images	O
,	O
usually	O
a	O
single	O
one	O
.	O
</s>
<s>
The	O
purpose	O
of	O
image	B-General_Concept
fusion	I-General_Concept
is	O
not	O
only	O
to	O
reduce	O
the	O
amount	O
of	O
data	O
but	O
also	O
to	O
construct	O
images	O
that	O
are	O
more	O
appropriate	O
and	O
understandable	O
for	O
the	O
human	O
and	O
machine	O
perception	O
.	O
</s>
<s>
In	O
computer	B-Application
vision	I-Application
,	O
multisensor	B-General_Concept
image	I-General_Concept
fusion	I-General_Concept
is	O
the	O
process	O
of	O
combining	O
relevant	O
information	O
from	O
two	O
or	O
more	O
images	O
into	O
a	O
single	O
image	O
.	O
</s>
<s>
In	O
remote	B-Application
sensing	I-Application
applications	O
,	O
the	O
increasing	O
availability	O
of	O
space	O
borne	O
sensors	O
gives	O
a	O
motivation	O
for	O
different	O
image	B-General_Concept
fusion	I-General_Concept
algorithms	O
.	O
</s>
<s>
Image	B-General_Concept
fusion	I-General_Concept
techniques	O
allow	O
the	O
integration	O
of	O
different	O
information	O
sources	O
.	O
</s>
<s>
However	O
,	O
the	O
standard	O
image	B-General_Concept
fusion	I-General_Concept
techniques	O
can	O
distort	O
the	O
spectral	O
information	O
of	O
the	O
multispectral	O
data	O
while	O
merging	O
.	O
</s>
<s>
Many	O
methods	O
exist	O
to	O
perform	O
image	B-General_Concept
fusion	I-General_Concept
.	O
</s>
<s>
Multi-focus	B-Algorithm
image	I-Algorithm
fusion	I-Algorithm
is	O
used	O
to	O
collect	O
useful	O
and	O
necessary	O
information	O
from	O
input	O
images	O
with	O
different	O
focus	O
depths	O
in	O
order	O
to	O
create	O
an	O
output	O
image	O
that	O
ideally	O
has	O
all	O
information	O
from	O
input	O
images	O
.	O
</s>
<s>
In	O
visual	B-Device
sensor	I-Device
network	I-Device
(	O
VSN	O
)	O
,	O
sensors	O
are	O
cameras	O
which	O
record	O
images	O
and	O
video	O
sequences	O
.	O
</s>
<s>
Multi-focus	B-Algorithm
image	I-Algorithm
fusion	I-Algorithm
is	O
a	O
process	O
which	O
combines	O
the	O
input	O
multi-focus	O
images	O
into	O
a	O
single	O
image	O
including	O
all	O
important	O
information	O
of	O
the	O
input	O
images	O
and	O
it	O
’s	O
more	O
accurate	O
explanation	O
of	O
the	O
scene	O
than	O
every	O
single	O
input	O
image	O
.	O
</s>
<s>
Multi	O
sensor	B-General_Concept
data	I-General_Concept
fusion	I-General_Concept
has	O
become	O
a	O
discipline	O
which	O
demands	O
more	O
general	O
formal	O
solutions	O
to	O
a	O
number	O
of	O
application	O
cases	O
.	O
</s>
<s>
This	O
is	O
important	O
in	O
remote	B-Application
sensing	I-Application
.	O
</s>
<s>
One	O
possible	O
solution	O
for	O
this	O
is	O
data	B-General_Concept
fusion	I-General_Concept
.	O
</s>
<s>
Image	B-General_Concept
fusion	I-General_Concept
methods	O
can	O
be	O
broadly	O
classified	O
into	O
two	O
groups	O
–	O
spatial	O
domain	O
fusion	O
and	O
transform	O
domain	O
fusion	O
.	O
</s>
<s>
The	O
fusion	O
methods	O
such	O
as	O
averaging	O
,	O
Brovey	O
method	O
,	O
principal	B-Application
component	I-Application
analysis	I-Application
(	O
PCA	B-Application
)	O
and	O
IHS	O
based	O
methods	O
fall	O
under	O
spatial	O
domain	O
approaches	O
.	O
</s>
<s>
Spatial	O
distortion	O
can	O
be	O
very	O
well	O
handled	O
by	O
frequency-domain	O
approaches	O
on	O
image	B-General_Concept
fusion	I-General_Concept
.	O
</s>
<s>
The	O
multiresolution	O
analysis	O
has	O
become	O
a	O
very	O
useful	O
tool	O
for	O
analysing	O
remote	B-Application
sensing	I-Application
images	O
.	O
</s>
<s>
The	O
images	O
used	O
in	O
image	B-General_Concept
fusion	I-General_Concept
should	O
already	O
be	O
registered	B-Algorithm
.	O
</s>
<s>
Misregistration	O
is	O
a	O
major	O
source	O
of	O
error	O
in	O
image	B-General_Concept
fusion	I-General_Concept
.	O
</s>
<s>
Some	O
well-known	O
image	B-General_Concept
fusion	I-General_Concept
methods	O
are	O
:	O
</s>
<s>
Image	B-General_Concept
fusion	I-General_Concept
in	O
remote	B-Application
sensing	I-Application
has	O
several	O
application	O
domains	O
.	O
</s>
<s>
An	O
important	O
domain	O
is	O
the	O
multi-resolution	O
image	B-General_Concept
fusion	I-General_Concept
(	O
commonly	O
referred	O
to	O
pan-sharpening	O
)	O
.	O
</s>
<s>
Image	B-General_Concept
fusion	I-General_Concept
attempts	O
to	O
merge	O
these	O
images	O
and	O
produce	O
a	O
single	O
high	O
resolution	O
multispectral	O
image	O
.	O
</s>
<s>
The	O
standard	O
merging	O
methods	O
of	O
image	B-General_Concept
fusion	I-General_Concept
are	O
based	O
on	O
Red	O
–	O
Green	O
–	O
Blue	O
(	O
RGB	O
)	O
to	O
Intensity	O
–	O
Hue	O
–	O
Saturation	O
(	O
IHS	O
)	O
transformation	O
.	O
</s>
<s>
The	O
usual	O
steps	O
involved	O
in	O
satellite	O
image	B-General_Concept
fusion	I-General_Concept
are	O
as	O
follows	O
:	O
</s>
<s>
This	O
is	O
usually	O
performed	O
by	O
histogram	B-Algorithm
matching	I-Algorithm
of	O
the	O
panchromatic	O
image	O
with	O
Intensity	O
component	O
of	O
the	O
multispectral	O
images	O
as	O
reference	O
.	O
</s>
<s>
Pan-sharpening	O
can	O
be	O
done	O
with	O
Photoshop	B-Operating_System
.	O
</s>
<s>
Other	O
applications	O
of	O
image	B-General_Concept
fusion	I-General_Concept
in	O
remote	B-Application
sensing	I-Application
are	O
available	O
.	O
</s>
<s>
Image	B-General_Concept
fusion	I-General_Concept
has	O
become	O
a	O
common	O
term	O
used	O
within	O
medical	O
diagnostics	O
and	O
treatment	O
.	O
</s>
<s>
The	O
term	O
is	O
used	O
when	O
multiple	O
images	O
of	O
a	O
patient	O
are	O
registered	B-Algorithm
and	O
overlaid	O
or	O
merged	O
to	O
provide	O
additional	O
information	O
.	O
</s>
<s>
Fused	O
images	O
may	O
be	O
created	O
from	O
multiple	O
images	O
from	O
the	O
same	O
imaging	O
modality	O
,	O
or	O
by	O
combining	O
information	O
from	O
multiple	O
modalities	O
,	O
such	O
as	O
magnetic	O
resonance	O
image	O
(	O
MRI	O
)	O
,	O
computed	O
tomography	O
(	O
CT	O
)	O
,	O
positron	B-Application
emission	I-Application
tomography	I-Application
(	O
PET	O
)	O
,	O
and	O
single-photon	O
emission	O
computed	O
tomography	O
(	O
SPECT	O
)	O
.	O
</s>
<s>
Comparative	O
analysis	O
of	O
image	B-General_Concept
fusion	I-General_Concept
methods	O
demonstrates	O
that	O
different	O
metrics	O
support	O
different	O
user	O
needs	O
,	O
sensitive	O
to	O
different	O
image	B-General_Concept
fusion	I-General_Concept
methods	O
,	O
and	O
need	O
to	O
be	O
tailored	O
to	O
the	O
application	O
.	O
</s>
<s>
Categories	O
of	O
image	B-General_Concept
fusion	I-General_Concept
metrics	O
are	O
based	O
on	O
information	O
theory	O
features	O
,	O
structural	O
similarity	O
,	O
or	O
human	O
perception	O
.	O
</s>
