IDFT on image is not working out well.. i did DFT it worked great but while implementing IDFT on that same image as of DFT output image , i didnt get my enitre original image back!?? help!!

my code is as following: apply DFT AND IDFT in same code

clc; close all; sum=0; a=imread('Cameraman.bmp');

b=a; M=50; N=50;

for x=1:50 for y=1:50 b(x,y)=a(x,y); end end c=double(b);

for u=1:M for v=1:N s=0; for x=1:M for y=1:N s=s+c(x,y)*exp(1*j*2*pi*(((u*x)/M)+((v*y)/N))); end end

                            F(u,v)=s;
                      end
end

for x=1:M for y=1:N s=0; for u=1:M for v=1:N s=s+F(u,v)*exp(-1*j*2*pi*(((u*x)/M)+((v*y)/N))); end end

                             inf(x,y)=s/(M*N);
                    end
          end

subplot(2,2,1); imshow(uint8(c)); title('ORIGINAL IMAGE');

subplot(2,2,2); imshow(uint8(F)); title('DFT IMAGE');

subplot(2,2,2); imshow(uint8(inf)); title('IDFT IMAGE');