<s>
Circular	B-Algorithm
thresholding	I-Algorithm
is	O
an	O
algorithm	O
for	O
automatic	B-Algorithm
image	I-Algorithm
threshold	I-Algorithm
selection	I-Algorithm
in	O
image	B-Algorithm
processing	I-Algorithm
.	O
</s>
<s>
However	O
,	O
some	O
quantities	O
such	O
as	O
hue	B-Language
and	O
orientation	O
are	O
a	O
circular	O
quantity	O
,	O
and	O
therefore	O
require	O
circular	B-Algorithm
thresholding	I-Algorithm
algorithms	O
.	O
</s>
<s>
The	O
example	O
shows	O
that	O
the	O
standard	O
linear	O
version	O
of	O
Otsu	B-Algorithm
's	I-Algorithm
method	I-Algorithm
when	O
applied	O
to	O
the	O
hue	B-Language
channel	O
of	O
an	O
image	O
of	O
blood	O
cells	O
fails	O
to	O
correctly	O
segment	O
the	O
large	O
white	O
blood	O
cells	O
(	O
leukocytes	O
)	O
.	O
</s>
<s>
In	O
contrast	O
the	O
white	O
blood	O
cells	O
are	O
correctly	O
segmented	O
by	O
the	O
circular	O
version	O
of	O
Otsu	B-Algorithm
's	I-Algorithm
method	I-Algorithm
.	O
</s>
<s>
The	O
following	O
examples	O
are	O
all	O
based	O
on	O
Otsu	B-Algorithm
's	I-Algorithm
method	I-Algorithm
for	O
linear	O
histograms	O
:	O
</s>
<s>
(	O
Tseng	O
,	O
Li	O
and	O
Tung	O
1995	O
)	O
smooth	O
the	O
circular	O
histogram	O
,	O
and	O
apply	O
Otsu	B-Algorithm
's	I-Algorithm
method	I-Algorithm
.	O
</s>
<s>
Otsu	B-Algorithm
's	I-Algorithm
method	I-Algorithm
and	O
histogram	O
rotation	O
are	O
applied	O
iteratively	O
until	O
several	O
heuristics	O
involving	O
class	O
size	O
,	O
threshold	O
location	O
,	O
and	O
class	O
variance	O
are	O
satisfied	O
.	O
</s>
<s>
Otsu	B-Algorithm
's	I-Algorithm
method	I-Algorithm
and	O
histogram	O
rotation	O
are	O
applied	O
iteratively	O
until	O
convergence	O
of	O
the	O
threshold	O
.	O
</s>
<s>
(	O
Lai	O
and	O
Rosin	O
2014	O
)	O
applied	O
Otsu	B-Algorithm
's	I-Algorithm
method	I-Algorithm
to	O
the	O
circular	O
histogram	O
.	O
</s>
<s>
For	O
the	O
two	O
class	O
circular	B-Algorithm
thresholding	I-Algorithm
task	O
they	O
showed	O
that	O
,	O
for	O
a	O
histogram	O
with	O
an	O
even	O
number	O
of	O
bins	O
,	O
the	O
optimal	O
solution	O
for	O
Otsu	O
's	O
criterion	O
of	O
within-class	O
variance	O
is	O
obtained	O
when	O
the	O
histogram	O
is	O
split	O
into	O
two	O
halves	O
.	O
</s>
<s>
D.-C	O
.	O
Tseng	O
,	O
Y.-F	O
.	O
Li	O
,	O
and	O
C.-T	O
.	O
Tung	O
,	O
Circular	O
histogram	O
thresholding	B-Algorithm
for	O
color	O
image	O
segmentation	O
in	O
Proc	O
.	O
</s>
<s>
Rosin	O
,	O
Efficient	O
Circular	B-Algorithm
Thresholding	I-Algorithm
,	O
IEEE	O
Trans	O
.	O
</s>
<s>
on	O
Image	B-Algorithm
Processing	I-Algorithm
23(3 )	O
,	O
992	O
–	O
1001	O
(	O
2014	O
)	O
.	O
</s>
