Contrast Enhancement Method Using Region-Based Dynamic Clipping Technique for LWIR-Based Thermal Camera of Night Vision Systems

. 2024 Jun 13;24(12):3829. doi: 10.3390/s24123829

Algorithm 1 Pseudo-Code for Proposed Contrast Enhancement Method Using Region-Based Histogram Equalization with Dynamic Clipping Technique

Input:

I_{I n}

: Input Image with N-bit format
Output:

I_{(O u t, L)}

: Contrast Enhanced Output Image

1:
< Automatic Gain Control (AGC) >
2:
$I_{I n . M a x}$ ← max $(I_{I n})$
3:
$I_{I n . M i n}$ ← min $(I_{I n})$
4:
$I_{8 b i t s}$ ← 255 × ( $I_{I n} - I_{I n . M i n}$ ) / ( $I_{I n . M a x} - I_{I n . M i n}$ )
5:
6:
< Histogram Bin Calculation >
7:
for $x \leftarrow 1$ to N do
8:
for $y \leftarrow 1$ to M do
9:
$H (I_{8 b i t s})$ ← $H (I_{8 b i t s})$ + 1
10:
end for
11:
end for
12:
13:
< Histogram Group Division >
14:
$H_{1}$ ← $H (0 : 63)$
15:
$H_{2}$ ← $H (64 : 127)$
16:
$H_{3}$ ← $H (128 : 191)$
17:
$H_{4}$ ← $H (192 : 255)$
18:
19:
< Histogram Clipping >
20:
for $L \leftarrow 1$ to 4 do
21:
$H_{L . M a x}$ ← max( $H_{L}$ )
22:
$H_{L . M i n}$ ← small( $H_{L}$ )
23:
[ $H_{L}$ , $E_{L}$ ] ← Clip( $H_{L}$ , $H_{L . M a x}$ , $H_{L . M i n}$ )
24:
end for
25:
36:
< Excess Value Distribution >
27:
$H_{C}$ ← [ $H_{1}$ , $H_{2}$ , $H_{3}$ , $H_{4}$ ]
28:
E ← $E_{1}$ + $E_{2}$ + $E_{3}$ + $E_{4}$
29:
$H_{C}$ ← $H_{C}$ + (E / 256)
30:
31:
< Output Value Mapping >
32:
C ← CDF( $H_{C}$ )
33:
P ← PDF(C)
34:
for $x \leftarrow 1$ to N do
35:
for $y \leftarrow 1$ to M do
36:
$O (x, y)$ ← 255 × $P (I_{8 b i t s})$
37:
end for
38:
end for