forensic_digital_image_analysis/JPEGBlockTechnique.m at master · math496/forensic_digital_image_analysis · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
function [  ] = JPEGBlockTechnique( imagearg, thresh )
%UNTITLED4 Summary of this function goes here
%   Detailed explanation goes here

image = imread(imagearg);
[m,n,z] = size(image);

if z == 3
    image = double( rgb2gray(image) );
else
    image = double( image );
end

j = 1;
w = waitbar(0);
while 8*j < m
    waitbar( 8*j/(3*m), w, 'Wait...' );
    i = 1;
    while 8*i < n
        value = image( 8*j, 8*i     ) - ...
                image( 8*j, 8*i + 1 ) - ...
                image( 8*j + 1, 8*i ) + ...
                image( 8*j + 1, 8*i + 1 );

            % Resets 64 px block to calculated val
            a = 8*(j-1) + 1;
            while a <= 8*i
                b = 8*(i-1) + 1;
                while b <= 8*i
                    image( a, b ) = value;
                    b = b + 1;
                end
                a = a + 1;
            end
            i = i + 1;
    end
    j = j + 1;
end

cnt = 8*j;

j = 1;
while 8*j < m
    waitbar( (cnt + 8*j)/3*m, w, 'Wait...');
    i = 1;
    while 8*i < n
        % Difference between...
        %   Left - Right
        difflr = abs( image( 8*j, 8*i ) - ...
                      image( 8*j, 8*i + 1 ));
        %   Up - Down
        diffud = abs( image( 8*j, 8*i ) - ...
                      image( 8*i + 1, 8*i ));

        if ((difflr >= thresh) || (diffud >= thresh ))

            % set all px in block to white
            a = 8*(j-1) + 1;
            while a <= 8*j
                b = 8*(i-1) + 1;
                while b <= 8*i
                    image( a, b ) = 255;
                    b = b + 1;
                end
                a = a + 1;
            end
        end
        i = i + 1;
    end
    j = j + 1;
end

cnt = 16*j;

% Sets nonwhite blocks to 0.
j = 1;
while  8*j < m
    waitbar( ( cnt + 8*j )/3*m, w, 'Almost there...');

    i = 1;
    while 8*i < n
        if ( image( 8*j, 8*i ) ~= 255 )
            a = 8*(j-1) + 1;
            while a <= 8*j
                b = 8*(i-1) + 1;
                while b <= 8*i
                    image( a, b ) = 0;
                    b = b + 1;
                end
                a = a + 1;
            end
        end
        i = i + 1;
    end
    j = j + 1;
end

i = 1;
while 8*i < n
    i = i + 1;
end
i = i - 1;

a = 1;

while a <= m
    b = 1;
    while 8*(i-1) + b <= n
        image( a, 8*(i-1) + b ) = 0;
        b = b + 1;
    end
    a = a + 1;
end

% Clean up next to last row
a = 1;
while a <= n
    b = 1;
    while 8*(j-2) + b  <= m
        image( 8*(j-2) + b, a ) = 0;
        b = b + 1;
    end
    a = a + 1;
end

close(w);

image = uint8( image );

imshow( image );

end