Image Processing Reference
In-Depth Information
Similar expressions can be derived for the remaining hue values. The only difference
is that the geometry in Fig. D.3 (b) is only valid when 0°
120°. The hue value
is therefore normalized, denoted H n , to this interval before being applied. The final
conversion from HSI to RGB therefore becomes
H
0 ,
if 0°
H
120°;
H n =
H
120° ,
if 120° <H
240°;
(D.23)
H
240° ,
if 240° <H < 360°
· 1
cos ( 60 ° H n ) ,
S
·
cos (H n )
+
I
if 0°
H
120°;
P R =
(D.24)
·
I
I
S,
if 120° <H
240°;
3 I
P G
P B ,
if 240° <H < 360°
3 I
P R
P B ,
if 0°
H
120°;
· 1
cos ( 60 ° H n ) ,
S
·
cos (H n )
I
+
if 120° <H
240°;
P G =
(D.25)
I
I
·
S,
if 240° <H < 360°
I
I
·
S,
if 0°
H
120°;
3 I
P R
P G ,
if 120° <H
240°;
P B =
(D.26)
· 1
cos ( 60 ° H n ) ,
S
·
cos (H n )
+
I
if 240° <H < 360°
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