Center Deviation Measurement of Color Contact Lenses Based on a Deep Learning Model and Hough Circle Transform

. 2023 Jul 19;23(14):6533. doi: 10.3390/s23146533

Algorithm 3: CalculatingHCT(img, dp, minDist, param1, param2, minRadius, maxRadius,

c e n t e r_{x},

c e n t e r_{y}, r a d i u s

)

//Detecting a circle to calculate the center of both CA and FA using HCT

Input

(1)

i m g

: an input image

(2)

dp : T h e i n v e r s e r a t i o o f t h e a c c u m u l a t o r r e s o l u t i o n t o t h e i m a g e r e s o l u t i o n

(3)

m i n D i s t

: M i n i m u m d i s t a n c e b e t w e e n t h e c e n t e r s o f t h e d e t e c t e d c i r c l e s

(4)

p a r a m 1 :

T h e h i g h e r t h r e s h o l d o f t h e t w o p a s s e d t o t h e C a n n y e d g e d e t e c t o r

(5)

p a r a m 2 :

A c c u m u l a t o r t h r e s h o l d f o r t h e c i r c l e c e n t e r s a t t h e d e t e c t i o n s t a g e

(6)

m i n R a d i u s :

M i n i m u m c i r c l e r a d i u s

(7)

m a x R a d i u s :

M a x i m u m c i r c l e r a d i u s

Output

(8)

c e n t e r_{x} : x c o o r d i n a t e o f t h e f i r s t c i r c l e ’ s c e n t e r

(9)

c e n t e r_{y} : y c o o r d i n a t e o f t h e f i r s t c i r c l e ’ s c e n t e r

(10)

r a d i u s : r a d i u s o f t h e f i r s t c i r c l e

Begin

g r a y \leftarrow C o n v e r t T o G r a y s c a l e (i m g)

b l u r e d \leftarrow A p p l y G a u s s i a n B l u r (g r a y)

e d g e s \leftarrow A p p l y C a n n y E d g e D e t e c t i o n (b l u r r e d, p a r a m 1)

h, w \leftarrow g e t t h e h e i g h t a n d w i d t h o f ‘ e d g e s ’

a c c u m u l a t o r \leftarrow c r e a t e a 3 D z e r o a r r a y o f s i z e (h, w, m a x R a d i u s - m i n R a d i u s)

F o r e a c h e d g e p o i n t (x_{e d g e}, y_{e d g e}) i n ‘ e d g e s ’ d o

F o r r i n r a n g e (m i n R a d i u s, m a x R a d i u s) d o

F o r t h e t a i n r a n g e (0, 360) d o

a \leftarrow x_{e d g e} - r * \cos (t h e t a)

10.

b \leftarrow y_{e d g e} - r * \sin (t h e t a)

11.

I f a a n d b a r e w i t h i n t h e i m a g e b o u n d a r i e s t h e n

12.

a c c u m u l a t o r [a, b, r - m i n R a d i u s] \leftarrow a c c u m u l a t o r [a, b, r - m i n R a d i u s] + 1

13.

E n d f o r

14.

E n d f o r

15.

E n d f o r

16.

m a x_a c c u m u l a t o r_v a l u e \leftarrow f i n d t h e m a x i m u m v a l u e i n ‘ a c c u m u l a t o r ’

17.

c i r c l e s

\leftarrow f i n d t h e (a, b, r) s u c h t h a t a c c u m u l a t o r [a, b, r] > p a r a m 2 * m a x_a c c u m u l a t o r_v a l u e

18.

c e n t e r_{x}, c e n t e r_{y}, r a d i u s \leftarrow c i r c l e s [0]

19.

R e t u r n c e n t e r_{x}, c e n t e r_{y}, r a d i u s

END