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??? Undefined function or method 'fftshow' for input arguments of type 'double'.

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Tricky
Tricky on 22 May 2012
Answered: Raghunathan P on 7 Apr 2021
Error ??? Undefined function or method 'fftshow' for input arguments of type 'double'.
when trying to display the image
c=imread('cameraman.tif');
cf=fftshift(fft2(c));
fftshow(cf,'abs')
or fftshow(cf,'log');
both are showing the same error how to overcome this

Answers (6)

Wayne King
Wayne King on 22 May 2012
What is fftshow.m ? That is not a MathWorks' function or method. If you have downloaded this MATLAB program from somewhere and saved it in a folder, then make sure you add that folder to the MATLAB search path with addpath or use pathtool.



yanqi liu
yanqi liu on 20 Feb 2021
sir, may be use the follow code
clc; clear all; close all;
c=imread('cameraman.tif');
cf=fftshift(fft2(c));
figure;
fftshow(cf,'abs')
figure;
fftshow(cf,'log');
function fftshow(f,type)
% from:https://ww2.mathworks.cn/matlabcentral/fileexchange/30947-gaussian-bandpass-filter-for-image-processing
% Usage: FFTSHOW(F,TYPE)
%
% Displays the fft matrix F using imshow, where TYPE must be one of
% 'abs' or 'log'. If TYPE='abs', then then abs(f) is displayed; if
% TYPE='log' then log(1+abs(f)) is displayed. If TYPE is omitted, then
% 'log' is chosen as a default.
%
% Example:
% c=imread('cameraman.tif');
% cf=fftshift(fft2(c));
% fftshow(cf,'abs')
%
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
end
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yanqi liu
yanqi liu on 20 Feb 2021
sir, please copy to one m file, like follows
clc; clear all; close all;
a=imread('Fig0441(a).tif');
% whos a
g=fspecial('gaussian',688,10);
if ndims(a) > 2
a = rgb2gray(a);
end
if ~isequal(size(a), size(g))
a = imresize(a, size(g), 'bilinear');
end
max(g(:));
g1=mat2gray(g);
max(g1(:));
f=fftshift(fft2(a));
i=f.*g1;
fftshow(i)
f1=ifft2(i);
figure; imshow(f1, []);
function fftshow(f,type)
% from:https://ww2.mathworks.cn/matlabcentral/fileexchange/30947-gaussian-bandpass-filter-for-image-processing
% Usage: FFTSHOW(F,TYPE)
%
% Displays the fft matrix F using imshow, where TYPE must be one of
% 'abs' or 'log'. If TYPE='abs', then then abs(f) is displayed; if
% TYPE='log' then log(1+abs(f)) is displayed. If TYPE is omitted, then
% 'log' is chosen as a default.
%
% Example:
% c=imread('cameraman.tif');
% cf=fftshift(fft2(c));
% fftshow(cf,'abs')
%
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
end

Raghunathan P
Raghunathan P on 7 Apr 2021
It is another library instead you can use this code:
c=imread('cameraman.tif');
cf=fftshift(fft2(c));
fl = log(1+abs(cf)); % Your DFT matrix of image 'cf' wil come HERE
fm = max(fl(:));
imshow(im2uint8(fl/fm))
or for advanced
function fftshow(f,type)
% Usage: FFTSHOW(F,TYPE)
%
% Displays the fft matrix F using imshow, where TYPE must be one of
% 'abs' or 'log'. If TYPE='abs', then then abs(f) is displayed; if
% TYPE='log' then log(1+abs(f)) is displayed. If TYPE is omitted, then
% 'log' is chosen as a default.
%
% Example:
% c=imread('cameraman.tif');
% cf=fftshift(fft2(c));
% fftshow(cf,'abs')
if nargin<2,
type='log';
end
if (type=='log')
fl = log(1+abs(f)); % Your matrix 'cf' wil come HERE instead of '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;

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