cooccurrence.m

glcm examples in matlab

% Calculates cooccurrence matrix 
% for a given direction and distance
%
% out = cooccurrence (input, dir, dist, symmetric);
%
% INPUT:
% input: input matrix of any size
%
% dir: direction of evaluation
%       "dir" value                    Angle
%              0                            0
%              1                           -45
%              2                           -90
%              3                           -135
%              4                           -180
%              5                           +135
%              6                           +90
%              7                           +45
%
% dist: distance between pixels
%
% symmetric:  1 for symmetric version
%                   0 for non-symmetric version
%
% eg: out = cooccurrence (input, 0, 1, 1);

% Author: Baran Aydogan (15.07.2006)
% RGI, Tampere University of Technology
% [e-mail]


function out = cooccurrence (input, dir, dist, symmetric);

input = round(input);
[r c] = size(input);

min_intensity = min(min(input));
max_intensity = max(max(input));

out = zeros(max_intensity-min_intensity+1);

if (dir == 0)
    dir_x = 0;
    dir_y = 1;
end

if (dir == 1)
    dir_x = 1;
    dir_y = 1;
end

if (dir == 2)
    dir_x = 1;
    dir_y = 0;
end

if (dir == 3)
    dir_x = 1;
    dir_y = -1;
end

if (dir == 4)
    dir_x = 0;
    dir_y = -1;
end

if (dir == 5)
    dir_x = -1;
    dir_y = -1;
end

if (dir == 6)
    dir_x = -1;
    dir_y = 0;
end

if (dir == 7)
    dir_x = -1;
    dir_y = 1;
end

dir_x = dir_x*dist;
dir_y = dir_y*dist;

out_ind_x = 0;
out_ind_y = 0;

for intensity1 = min_intensity:max_intensity
    out_ind_x = out_ind_x + 1;
    out_ind_y = 0;
    
    [ind_x1 ind_y1] = find (input == intensity1);
    ind_x1 = ind_x1 + dir_x;
    ind_y1 = ind_y1 + dir_y;
    
    for intensity2 = min_intensity:max_intensity    
        out_ind_y = out_ind_y + 1;        
    
        [ind_x2 ind_y2] = find (input == intensity2);
        
        count = 0;
        
        for i = 1:size(ind_x1,1)            
            for j = 1:size(ind_x2,1)                
                if ( (ind_x1(i) == ind_x2(j)) && (ind_y1(i) == ind_y2(j)) )
                    count = count + 1;
                end                
            end                
        end
        
        out(out_ind_x, out_ind_y) = count;
            
    end
end

if (symmetric)
    
    if (dir < 4)
        dir = dir + 4;
    else
        dir = mod(dir,4);
    end 
        
    out = out + cooccurrence (input, dir, dist, 0);    
end