I'm stuck in a loop when trying to do image processing.

Hello, I have written this code to filter an image however the outputted image never appears, does anyone know what I am doing wrong?

clc;
clear all;
close all;

im1=imread('peppers.png');
im3=im2double(im1);
[n,m]=size(im3);

c1=0;
h = waitbar(0,'Calculating XXX please wait......'); 
k=1;l=1;
for l=0:1:m-1
    for k=0:1:n-1
        for x=0:1:n-1
            for y=0:1:m-1
                a=x+1;b=y+1;
                c= im3(a,b) * exp(-1i*2*pi*(k*x/n + l*y/m));
                c1=c1+c;
            end
        end
        aa=l+1;bb=k+1;
        im(bb,aa)=c1;
        c1=0;
    end
    waitbar(l / m);
end
ims = im*255;
close(h)

imshow(ims);title('XXX plot');
figure
imshow(log(abs(ims)),[-1 5]); colormap(jet); colorbar;title('absolute value of XXX plot');

[Rik]

I think your loop was still working. You should really start with a small example when you have nested loops. I replaced the inner two loops with vectorized code and still it took 20 seconds to get the outermost loop to 5. See my edit and comments below.

You should re-think what you want to calculate and how you want to do it.

clc;
clear variables;%don't use clear all, there is no reason to
close all;
im1=imread('peppers.png');
im3=im2double(im1);
im3=mean(im3,3);%convert RGB to grayscale
[n,m]=size(im3);
c1=0;
h = waitbar(0,'Calculating XXX please wait......'); 
k=1;l=1;tic
for l=0:1:m-1
    for k=0:1:n-1
        if toc>20,break,end%if it takes too much time, exit the loop
        [y,x]=meshgrid(0:1:m-1,0:1:n-1);
        a=x+1;b=y+1;
        aaa=exp(-1i*2*pi*(k*x/n + l*y/m));
        c= im3.* exp(-1i*2*pi*(k*x/n + l*y/m));
        c1=c1+sum(c(:));
        aa=l+1;bb=k+1;
        im(bb,aa)=c1;
        c1=0;
    end
    waitbar(l / m);
end
ims = im*255;
close(h)

[Rik]

For future people stumbling onto this post, a continued discussion and a working solution are posted here.