A Computational Introduction to Digital Image Processing, 2nd Edition

The Fourier Transform 189

MATLAB/Octave

if nargin

<2,

type=’log’;

end

if (type==’log’)

fl = log(1+abs(f));

fm =

max

(fl(:));

imshow(im2uint8(fl/fm))

elseif (type==’abs’)

fa=abs(f);

fm=max(fa(:));

imshow(fa/fm)

else

error(’TYPE

must be abs or log.’);

end;

And here is

homfilt

first f or MATLAB or Octave:

MATLAB/Octave

function res=homfilt(im,cutoff,order,lowgain,highgain)

% HOMFILT(IMAGE,FILTER) applies homomorphic filtering to the image IMAGE

% with the given parameters

u = im2uint8(im);

height = size(im,1);

width = size(im,2);

[x,y] = meshgrid(-floor(width/2):floor((width-1)/2),...

-floor(height/2):floor((height-1)/2));

lbutter = 1./(1+(sqrt(2)-1)

*

((x.^2+y.^2)/cutoff^2).^order); ...