study notes
Image segmentation
μ
R
: mean pixel value
def mean squared error:
E
(
R
)
=
∑
s
∈
R
(
y
s
−
μ
R
)
2
with
(
y
s
−
μ
R
)
2
=
y
s
2
−
2
y
s
m
y
R
+
μ
R
2
=>
∑
s
∈
R
(
y
s
−
μ
R
)
2
=
∑
s
∈
R
y
s
2
−
2
∑
s
∈
R
y
s
m
y
R
+
∑
s
∈
R
μ
R
2
=
area_square_sum
−
2
⋅
mean
⋅
area
+
mean
2
⋅
area