<s>
Digital	B-Algorithm
image	I-Algorithm
processing	O
is	O
the	O
use	O
of	O
a	O
digital	O
computer	O
to	O
process	O
digital	B-Algorithm
images	I-Algorithm
through	O
an	O
algorithm	O
.	O
</s>
<s>
As	O
a	O
subcategory	O
or	O
field	O
of	O
digital	B-General_Concept
signal	I-General_Concept
processing	I-General_Concept
,	O
digital	B-Algorithm
image	I-Algorithm
processing	O
has	O
many	O
advantages	O
over	O
analog	B-Algorithm
image	I-Algorithm
processing	I-Algorithm
.	O
</s>
<s>
It	O
allows	O
a	O
much	O
wider	O
range	O
of	O
algorithms	O
to	O
be	O
applied	O
to	O
the	O
input	O
data	O
and	O
can	O
avoid	O
problems	O
such	O
as	O
the	O
build-up	O
of	O
noise	B-Algorithm
and	O
distortion	O
during	O
processing	O
.	O
</s>
<s>
Since	O
images	O
are	O
defined	O
over	O
two	O
dimensions	O
(	O
perhaps	O
more	O
)	O
digital	B-Algorithm
image	I-Algorithm
processing	O
may	O
be	O
modeled	O
in	O
the	O
form	O
of	O
multidimensional	O
systems	O
.	O
</s>
<s>
The	O
generation	O
and	O
development	O
of	O
digital	B-Algorithm
image	I-Algorithm
processing	O
are	O
mainly	O
affected	O
by	O
three	O
factors	O
:	O
first	O
,	O
the	O
development	O
of	O
computers	O
;	O
second	O
,	O
the	O
development	O
of	O
mathematics	O
(	O
especially	O
the	O
creation	O
and	O
improvement	O
of	O
discrete	O
mathematics	O
theory	O
)	O
;	O
third	O
,	O
the	O
demand	O
for	O
a	O
wide	O
range	O
of	O
applications	O
in	O
environment	O
,	O
agriculture	O
,	O
military	O
,	O
industry	O
and	O
medical	O
science	O
has	O
increased	O
.	O
</s>
<s>
Many	O
of	O
the	O
techniques	O
of	O
digital	B-Algorithm
image	I-Algorithm
processing	O
,	O
or	O
digital	B-Algorithm
picture	I-Algorithm
processing	O
as	O
it	O
often	O
was	O
called	O
,	O
were	O
developed	O
in	O
the	O
1960s	O
,	O
at	O
Bell	O
Laboratories	O
,	O
the	O
Jet	O
Propulsion	O
Laboratory	O
,	O
Massachusetts	O
Institute	O
of	O
Technology	O
,	O
University	O
of	O
Maryland	O
,	O
and	O
a	O
few	O
other	O
research	O
facilities	O
,	O
with	O
application	O
to	O
satellite	O
imagery	O
,	O
wire-photo	O
standards	O
conversion	O
,	O
medical	O
imaging	O
,	O
videophone	B-Application
,	O
character	B-Application
recognition	I-Application
,	O
and	O
photograph	O
enhancement	O
.	O
</s>
<s>
The	O
purpose	O
of	O
early	O
image	B-Algorithm
processing	I-Algorithm
was	O
to	O
improve	O
the	O
quality	O
of	O
the	O
image	O
.	O
</s>
<s>
In	O
image	B-Algorithm
processing	I-Algorithm
,	O
the	O
input	O
is	O
a	O
low-quality	O
image	O
,	O
and	O
the	O
output	O
is	O
an	O
image	O
with	O
improved	O
quality	O
.	O
</s>
<s>
Common	O
image	B-Algorithm
processing	I-Algorithm
include	O
image	B-Application
enhancement	I-Application
,	O
restoration	O
,	O
encoding	B-Algorithm
,	O
and	O
compression	O
.	O
</s>
<s>
They	O
used	O
image	B-Algorithm
processing	I-Algorithm
techniques	O
such	O
as	O
geometric	O
correction	O
,	O
gradation	O
transformation	O
,	O
noise	B-Algorithm
removal	O
,	O
etc	O
.	O
</s>
<s>
Later	O
,	O
more	O
complex	O
image	B-Algorithm
processing	I-Algorithm
was	O
performed	O
on	O
the	O
nearly	O
100,000	O
photos	O
sent	O
back	O
by	O
the	O
spacecraft	O
,	O
so	O
that	O
the	O
topographic	O
map	O
,	O
color	O
map	O
and	O
panoramic	O
mosaic	O
of	O
the	O
moon	O
were	O
obtained	O
,	O
which	O
achieved	O
extraordinary	O
results	O
and	O
laid	O
a	O
solid	O
foundation	O
for	O
human	O
landing	O
on	O
the	O
moon	O
.	O
</s>
<s>
That	O
changed	O
in	O
the	O
1970s	O
,	O
when	O
digital	B-Algorithm
image	I-Algorithm
processing	O
proliferated	O
as	O
cheaper	O
computers	O
and	O
dedicated	O
hardware	O
became	O
available	O
.	O
</s>
<s>
With	O
the	O
fast	O
computers	O
and	O
signal	O
processors	O
available	O
in	O
the	O
2000s	O
,	O
digital	B-Algorithm
image	B-Algorithm
processing	I-Algorithm
has	O
become	O
the	O
most	O
common	O
form	O
of	O
image	B-Algorithm
processing	I-Algorithm
,	O
and	O
is	O
generally	O
used	O
because	O
it	O
is	O
not	O
only	O
the	O
most	O
versatile	O
method	O
,	O
but	O
also	O
the	O
cheapest	O
.	O
</s>
<s>
The	O
basis	O
for	O
modern	O
image	B-Algorithm
sensors	I-Algorithm
is	O
metal	B-Architecture
–	I-Architecture
oxide	I-Architecture
–	I-Architecture
semiconductor	I-Architecture
(	O
MOS	O
)	O
technology	O
,	O
which	O
originates	O
from	O
the	O
invention	O
of	O
the	O
MOSFET	B-Architecture
(	O
MOS	O
field-effect	O
transistor	O
)	O
by	O
Mohamed	O
M	O
.	O
Atalla	O
and	O
Dawon	O
Kahng	O
at	O
Bell	O
Labs	O
in	O
1959	O
.	O
</s>
<s>
This	O
led	O
to	O
the	O
development	O
of	O
digital	O
semiconductor	O
image	B-Algorithm
sensors	I-Algorithm
,	O
including	O
the	O
charge-coupled	B-Algorithm
device	I-Algorithm
(	O
CCD	O
)	O
and	O
later	O
the	O
CMOS	B-Architecture
sensor	I-Architecture
.	O
</s>
<s>
The	O
charge-coupled	B-Algorithm
device	I-Algorithm
was	O
invented	O
by	O
Willard	O
S	O
.	O
Boyle	O
and	O
George	O
E	O
.	O
Smith	O
at	O
Bell	O
Labs	O
in	O
1969	O
.	O
</s>
<s>
While	O
researching	O
MOS	B-Architecture
technology	I-Architecture
,	O
they	O
realized	O
that	O
an	O
electric	O
charge	O
was	O
the	O
analogy	O
of	O
the	O
magnetic	O
bubble	O
and	O
that	O
it	O
could	O
be	O
stored	O
on	O
a	O
tiny	O
MOS	O
capacitor	O
.	O
</s>
<s>
As	O
it	O
was	O
fairly	O
straightforward	O
to	O
fabricate	B-Architecture
a	O
series	O
of	O
MOS	O
capacitors	O
in	O
a	O
row	O
,	O
they	O
connected	O
a	O
suitable	O
voltage	O
to	O
them	O
so	O
that	O
the	O
charge	O
could	O
be	O
stepped	O
along	O
from	O
one	O
to	O
the	O
next	O
.	O
</s>
<s>
The	O
NMOS	B-Algorithm
active-pixel	B-Architecture
sensor	I-Architecture
(	O
APS	O
)	O
was	O
invented	O
by	O
Olympus	O
in	O
Japan	O
during	O
the	O
mid-1980s	O
.	O
</s>
<s>
This	O
was	O
enabled	O
by	O
advances	O
in	O
MOS	O
semiconductor	B-Architecture
device	I-Architecture
fabrication	I-Architecture
,	O
with	O
MOSFET	B-Architecture
scaling	O
reaching	O
smaller	O
micron	B-Algorithm
and	I-Algorithm
then	I-Algorithm
sub-micron	I-Algorithm
levels	O
.	O
</s>
<s>
The	O
NMOS	B-Algorithm
APS	O
was	O
fabricated	O
by	O
Tsutomu	O
Nakamura	O
's	O
team	O
at	O
Olympus	O
in	O
1985	O
.	O
</s>
<s>
The	O
CMOS	B-Device
active-pixel	B-Architecture
sensor	I-Architecture
(	O
CMOS	B-Architecture
sensor	I-Architecture
)	O
was	O
later	O
developed	O
by	O
Eric	O
Fossum	O
's	O
team	O
at	O
the	O
NASA	O
Jet	O
Propulsion	O
Laboratory	O
in	O
1993	O
.	O
</s>
<s>
By	O
2007	O
,	O
sales	O
of	O
CMOS	B-Architecture
sensors	I-Architecture
had	O
surpassed	O
CCD	B-Algorithm
sensors	I-Algorithm
.	O
</s>
<s>
An	O
important	O
development	O
in	O
digital	B-Algorithm
image	I-Algorithm
compression	O
technology	O
was	O
the	O
discrete	B-General_Concept
cosine	I-General_Concept
transform	I-General_Concept
(	O
DCT	B-General_Concept
)	O
,	O
a	O
lossy	B-Algorithm
compression	I-Algorithm
technique	O
first	O
proposed	O
by	O
Nasir	O
Ahmed	O
in	O
1972	O
.	O
</s>
<s>
DCT	B-General_Concept
compression	O
became	O
the	O
basis	O
for	O
JPEG	O
,	O
which	O
was	O
introduced	O
by	O
the	O
Joint	O
Photographic	O
Experts	O
Group	O
in	O
1992	O
.	O
</s>
<s>
Its	O
highly	O
efficient	O
DCT	B-General_Concept
compression	O
algorithm	O
was	O
largely	O
responsible	O
for	O
the	O
wide	O
proliferation	O
of	O
digital	B-Algorithm
images	I-Algorithm
and	O
digital	B-Application
photos	I-Application
,	O
with	O
several	O
billion	O
JPEG	O
images	O
produced	O
every	O
day	O
.	O
</s>
<s>
Electronic	O
signal	O
processing	O
was	O
revolutionized	O
by	O
the	O
wide	O
adoption	O
of	O
MOS	B-Architecture
technology	I-Architecture
in	O
the	O
1970s	O
.	O
</s>
<s>
MOS	O
integrated	O
circuit	O
technology	O
was	O
the	O
basis	O
for	O
the	O
first	O
single-chip	O
microprocessors	B-Architecture
and	O
microcontrollers	B-Architecture
in	O
the	O
early	O
1970s	O
,	O
and	O
then	O
the	O
first	O
single-chip	O
digital	B-Architecture
signal	I-Architecture
processor	I-Architecture
(	O
DSP	O
)	O
chips	O
in	O
the	O
late	O
1970s	O
.	O
</s>
<s>
DSP	B-Architecture
chips	I-Architecture
have	O
since	O
been	O
widely	O
used	O
in	O
digital	B-Algorithm
image	I-Algorithm
processing	O
.	O
</s>
<s>
The	O
discrete	B-General_Concept
cosine	I-General_Concept
transform	I-General_Concept
(	O
DCT	B-General_Concept
)	O
image	B-General_Concept
compression	I-General_Concept
algorithm	O
has	O
been	O
widely	O
implemented	O
in	O
DSP	B-Architecture
chips	I-Architecture
,	O
with	O
many	O
companies	O
developing	O
DSP	B-Architecture
chips	I-Architecture
based	O
on	O
DCT	B-General_Concept
technology	O
.	O
</s>
<s>
DCTs	B-General_Concept
are	O
widely	O
used	O
for	O
encoding	B-Algorithm
,	O
decoding	O
,	O
video	B-Algorithm
coding	I-Algorithm
,	O
audio	O
coding	O
,	O
multiplexing	B-Architecture
,	O
control	O
signals	O
,	O
signaling	O
,	O
analog-to-digital	O
conversion	O
,	O
formatting	O
luminance	O
and	O
color	O
differences	O
,	O
and	O
color	O
formats	O
such	O
as	O
YUV444	O
and	O
YUV411	O
.	O
</s>
<s>
DCTs	B-General_Concept
are	O
also	O
used	O
for	O
encoding	B-Algorithm
operations	O
such	O
as	O
motion	O
estimation	O
,	O
motion	B-Algorithm
compensation	I-Algorithm
,	O
inter-frame	B-Algorithm
prediction	O
,	O
quantization	B-Algorithm
,	O
perceptual	O
weighting	O
,	O
entropy	B-Algorithm
encoding	I-Algorithm
,	O
variable	O
encoding	B-Algorithm
,	O
and	O
motion	O
vectors	O
,	O
and	O
decoding	O
operations	O
such	O
as	O
the	O
inverse	O
operation	O
between	O
different	O
color	O
formats	O
(	O
YIQ	O
,	O
YUV	O
and	O
RGB	O
)	O
for	O
display	O
purposes	O
.	O
</s>
<s>
DCTs	B-General_Concept
are	O
also	O
commonly	O
used	O
for	O
high-definition	B-Device
television	I-Device
(	O
HDTV	B-Device
)	O
encoder/decoder	O
chips	O
.	O
</s>
<s>
The	O
CT	O
nucleus	O
method	O
is	O
based	O
on	O
the	O
projection	B-Algorithm
of	O
the	O
human	O
head	O
section	O
and	O
is	O
processed	O
by	O
computer	O
to	O
reconstruct	O
the	O
cross-sectional	O
image	O
,	O
which	O
is	O
called	O
image	O
reconstruction	O
.	O
</s>
<s>
Digital	B-Algorithm
image	I-Algorithm
processing	O
technology	O
for	O
medical	O
applications	O
was	O
inducted	O
into	O
the	O
Space	O
Foundation	O
Space	O
Technology	O
Hall	O
of	O
Fame	O
in	O
1994	O
.	O
</s>
<s>
Digital	B-Algorithm
image	I-Algorithm
processing	O
allows	O
the	O
use	O
of	O
much	O
more	O
complex	O
algorithms	O
,	O
and	O
hence	O
,	O
can	O
offer	O
both	O
more	O
sophisticated	O
performance	O
at	O
simple	O
tasks	O
,	O
and	O
the	O
implementation	O
of	O
methods	O
which	O
would	O
be	O
impossible	O
by	O
analogue	O
means	O
.	O
</s>
<s>
In	O
particular	O
,	O
digital	B-Algorithm
image	I-Algorithm
processing	O
is	O
a	O
concrete	O
application	O
of	O
,	O
and	O
a	O
practical	O
technology	O
based	O
on	O
:	O
</s>
<s>
Some	O
techniques	O
which	O
are	O
used	O
in	O
digital	B-Algorithm
image	I-Algorithm
processing	O
include	O
:	O
</s>
<s>
Digital	O
filters	O
are	O
used	O
to	O
blur	O
and	O
sharpen	O
digital	B-Algorithm
images	I-Algorithm
.	O
</s>
<s>
Affine	B-Algorithm
transformations	I-Algorithm
enable	O
basic	O
image	O
transformations	O
including	O
scale	O
,	O
rotate	O
,	O
translate	O
,	O
mirror	O
and	O
shear	B-Algorithm
as	O
is	O
shown	O
in	O
the	O
following	O
examples	O
:	O
</s>
<s>
Because	O
matrix	O
multiplication	O
is	O
associative	O
,	O
multiple	O
affine	B-Algorithm
transformations	I-Algorithm
can	O
be	O
combined	O
into	O
a	O
single	O
affine	B-Algorithm
transformation	I-Algorithm
by	O
multiplying	O
the	O
matrix	O
of	O
each	O
individual	O
transformation	O
in	O
the	O
order	O
that	O
the	O
transformations	O
are	O
done	O
.	O
</s>
<s>
Thus	O
a	O
sequence	O
of	O
affine	B-Algorithm
transformation	I-Algorithm
matrices	O
can	O
be	O
reduced	O
to	O
a	O
single	O
affine	B-Algorithm
transformation	I-Algorithm
matrix	I-Algorithm
.	O
</s>
<s>
These	O
3	O
affine	B-Algorithm
transformations	I-Algorithm
can	O
be	O
combined	O
into	O
a	O
single	O
matrix	O
,	O
thus	O
allowing	O
rotation	O
around	O
any	O
point	O
in	O
the	O
image	O
.	O
</s>
<s>
Mathematical	B-Algorithm
morphology	I-Algorithm
is	O
suitable	O
for	O
denoising	O
images	O
.	O
</s>
<s>
Structuring	B-Algorithm
element	I-Algorithm
are	O
important	O
in	O
Mathematical	B-Algorithm
morphology	I-Algorithm
.	O
</s>
<s>
The	O
following	O
examples	O
are	O
about	O
Structuring	B-Algorithm
elements	I-Algorithm
.	O
</s>
<s>
The	O
denoise	O
function	O
,	O
image	O
as	O
I	O
,	O
and	O
structuring	B-Algorithm
element	I-Algorithm
as	O
B	O
are	O
shown	O
as	O
below	O
and	O
table	O
.	O
</s>
<s>
Define	O
Dilation(I, B )	O
(	O
i	O
,	O
j	O
)	O
=	O
.	O
</s>
<s>
Define	O
Erosion(I, B )	O
(	O
i	O
,	O
j	O
)	O
=	O
.	O
</s>
<s>
An	O
opening	B-Algorithm
method	O
is	O
just	O
simply	O
erosion	B-Algorithm
first	O
,	O
and	O
then	O
dilation	B-Algorithm
while	O
the	O
closing	B-Algorithm
method	O
is	O
vice	O
versa	O
.	O
</s>
<s>
Convolution	B-Language
Neighbor	O
and	O
structuring	B-Algorithm
element	I-Algorithm
and	O
then	O
replace	O
the	O
center	O
with	O
a	O
minimum	O
of	O
neighbor	O
.	O
</s>
<s>
Take	O
the	O
Closing	B-Algorithm
method	O
for	O
example	O
.	O
</s>
<s>
structuring	B-Algorithm
elements	I-Algorithm
depend	O
on	O
your	O
dilation	B-Algorithm
or	O
erosion	B-Algorithm
function	O
.	O
</s>
<s>
The	O
minimum	O
of	O
the	O
neighbor	O
of	O
a	O
pixel	O
leads	O
to	O
an	O
erosion	B-Algorithm
method	O
and	O
the	O
maximum	O
of	O
neighbor	O
leads	O
to	O
a	O
dilation	B-Algorithm
method	O
.	O
</s>
<s>
Set	O
the	O
time	O
for	O
dilation	B-Algorithm
,	O
erosion	B-Algorithm
,	O
and	O
closing	B-Algorithm
.	O
</s>
<s>
Dilation	B-Algorithm
first	O
with	O
structuring	O
window	O
.	O
</s>
<s>
Erosion	B-Algorithm
with	O
structuring	O
window	O
.	O
</s>
<s>
Digital	O
cameras	O
generally	O
include	O
specialized	O
digital	B-Algorithm
image	I-Algorithm
processing	O
hardware	O
–	O
either	O
dedicated	O
chips	O
or	O
added	O
circuitry	O
on	O
other	O
chips	O
–	O
to	O
convert	O
the	O
raw	O
data	O
from	O
their	O
image	B-Algorithm
sensor	I-Algorithm
into	O
a	O
color-corrected	O
image	O
in	O
a	O
standard	O
image	O
file	O
format	O
.	O
</s>
<s>
Westworld	O
(	O
1973	O
)	O
was	O
the	O
first	O
feature	O
film	O
to	O
use	O
the	O
digital	B-Algorithm
image	I-Algorithm
processing	O
to	O
pixellate	B-Algorithm
photography	O
to	O
simulate	O
an	O
android	O
's	O
point	O
of	O
view	O
.	O
</s>
<s>
Image	B-Algorithm
processing	I-Algorithm
is	O
also	O
vastly	O
used	O
to	O
produce	O
the	O
chroma	O
key	O
effect	O
that	O
replaces	O
the	O
background	O
of	O
actors	O
with	O
natural	O
or	O
artistic	O
scenery	O
.	O
</s>
<s>
Face	B-General_Concept
detection	I-General_Concept
can	O
be	O
implemented	O
with	O
Mathematical	B-Algorithm
morphology	I-Algorithm
,	O
Discrete	B-General_Concept
cosine	I-General_Concept
transform	I-General_Concept
which	O
is	O
usually	O
called	O
DCT	B-General_Concept
,	O
and	O
horizontal	O
Projection	B-Algorithm
(	O
mathematics	O
)	O
.	O
</s>
<s>
The	O
feature-based	O
method	O
of	O
face	B-General_Concept
detection	I-General_Concept
is	O
using	O
skin	O
tone	O
,	O
edge	B-Algorithm
detection	I-Algorithm
,	O
face	O
shape	O
,	O
and	O
feature	O
of	O
a	O
face	O
(	O
like	O
eyes	O
,	O
mouth	O
,	O
etc	O
.	O
)	O
</s>
<s>
to	O
achieve	O
face	B-General_Concept
detection	I-General_Concept
.	O
</s>
<s>
Structural	B-Algorithm
similarity	I-Algorithm
index	O
measure	O
(	O
SSIM	B-Algorithm
)	O
can	O
be	O
applied	O
to	O
compare	O
images	O
in	O
terms	O
of	O
extracting	O
the	O
skin	O
tone	O
.	O
</s>
<s>
After	O
filtering	O
images	O
with	O
skin	O
tone	O
,	O
to	O
get	O
the	O
face	O
edge	O
,	O
morphology	O
and	O
DCT	B-General_Concept
are	O
used	O
to	O
remove	O
noise	B-Algorithm
and	O
fill	O
up	O
missing	O
skin	O
areas	O
.	O
</s>
<s>
Opening	B-Algorithm
method	O
or	O
closing	B-Algorithm
method	O
can	O
be	O
used	O
to	O
achieve	O
filling	O
up	O
missing	O
skin	O
.	O
</s>
<s>
DCT	B-General_Concept
is	O
to	O
avoid	O
the	O
object	O
with	O
tone-like	O
skin	O
.	O
</s>
<s>
To	O
position	O
human	O
features	O
like	O
eyes	O
,	O
using	O
the	O
projection	B-Algorithm
and	O
find	O
the	O
peak	O
of	O
the	O
histogram	O
of	O
projection	B-Algorithm
help	O
to	O
get	O
the	O
detail	O
feature	O
like	O
mouse	O
,	O
hair	O
,	O
and	O
lip	O
.	O
</s>
<s>
Projection	B-Algorithm
is	O
just	O
projecting	O
the	O
image	O
to	O
see	O
the	O
high	O
frequency	O
which	O
is	O
usually	O
the	O
feature	O
position	O
.	O
</s>
<s>
Image	O
quality	O
can	O
be	O
influenced	O
by	O
camera	O
vibration	O
,	O
over-exposure	O
,	O
gray	O
level	O
distribution	O
too	O
centralized	O
,	O
and	O
noise	B-Algorithm
,	O
etc	O
.	O
</s>
<s>
For	O
example	O
,	O
noise	B-Algorithm
problem	O
can	O
be	O
solved	O
by	O
Smoothing	B-Application
method	O
while	O
gray	O
level	O
distribution	O
problem	O
can	O
be	O
improved	O
by	O
Histogram	B-Algorithm
Equalization	I-Algorithm
.	O
</s>
<s>
This	O
is	O
an	O
easy	O
way	O
to	O
think	O
of	O
Smoothing	B-Application
method	O
.	O
</s>
<s>
Smoothing	B-Application
method	O
can	O
be	O
implemented	O
with	O
mask	O
and	O
Convolution	B-Language
.	O
</s>
<s>
After	O
smoothing	B-Application
mask	O
,	O
the	O
pixel	O
becomes	O
9	O
,	O
10	O
,	O
9	O
,	O
9	O
respectively	O
.	O
</s>
<s>
Changing	O
the	O
histogram	O
to	O
uniform	O
distribution	O
from	O
an	O
image	O
is	O
usually	O
what	O
we	O
called	O
Histogram	B-Algorithm
equalization	I-Algorithm
.	O
</s>
