what is problem in the following matlab codes

Question

img=imread('img27.jpg');

%function rectangle=rect_test(img)

% edge detection

[gx,gy]=gradient(img); 

gx=abs(gx);
 gy=abs(gy);
g=gx+gy;

g=abs(g);

% make it 300x300

img=zeros(300);

s=size(g);

img(1:s(1),1:s(2))=g;

figure; 
imagesc((img));
 colormap(gray);
 title('Edge detection')


% take the dct of the image

IM=abs(dct2(img));
figure;
 imagesc((IM));
 colormap(gray); 
title('DCT')

% normalize

m=max(max(IM)); IM2=IM./m*100;

% get rid of the peak

size_IM2=size(IM2);
IM2(1:round(.05*size_IM2(1)),1:round(.05*size_IM2(2))) = 0;

% threshold
L=length( find(IM2>20)) ;


if( L > 60 )
   ret = 1;
else
   ret = 0;
end

Answer 1

I guess that the function doesn't work if you uncomment the line function rectangle=rect_test(img). That is most likely because in your function, the variable rectangle is never defined. Probably you want to write ret=rect_test(img) instead.