help to fix this

clear all
clc
global Gdi
global c
O=imread('12.jpg');
D1= im2double(O);
for ng=1:3
 XD=D1(:,:,ng);
[lg,cg]=size(XD);
lg1=lg/8;
lg2=fix(lg1);
g1=lg2*8;
cg1=cg/8;
cg2=fix(cg1);
g2=cg2*8;
ofs = ones(g1,g2)*128;
p=0;
t=1;
v=1;
while v<=(g1-7)
   while t<=(g2-7)
      pix=XD(v:(v+7),t:(t+7));
      pig=pix*256;
      pg=fix(pig);
   p=p+1;
Gm(:,:,p)=pg(:,:,1);
 %____________________________________________________________________     
   for i=1:1:1
   for j=1:1:8
      b(i,j)=1/sqrt(8);
   end
   end
        for  i=2:1:8
          for j=1:1:8
          b(i,j)=sqrt(.25)*cos((2*(j-1)+1)*(i-1)*pi/16); 
          end
        end
   %dtr=b';
      c(:,:,p)=b*Gm(:,:,p);
      d(:,:,p)=c(:,:,p)*b';      
    t=t+8;

     end
     t=1;
     v=v+8;

end
for z=1:p  
   n=[3 5 7 9 11 13 15 17;
      5 7 9 11 13 15 17 19;
      7 9 11 13 15 17 19 21;
      9 11 13 15 17 19 21 23;
      11 13 15 17 19 21 23 25;
      13 15 17 19 21 23 25 27;
      15 17 19 21 23 25 27 29;
      17 19 21 23 25 27 29 31];
   QG(:,:,z)=d(:,:,z)./n;
   DQG(:,:,z)=fix(QG(:,:,z));

      %$$$$$$$$$   DECOMPRESSION   $$$$$$$$$$$$$$$$$$$$$$$
     GDCTi(:,:,z)=DQG(:,:,z).*n;
     Go(:,:,z)= IDCT (GDCTi(:,:,z));
     for i=1:1:1
     for j=1:1:8
        b(i,j)=1/sqrt(8); 
     end
     end
          for  i=2:1:8
            for j=1:1:8
            b(i,j)=sqrt(.25)*cos((2*(j-1)+1)*(i-1)*pi/16); 
            end
          end
     %dtr=b';
        c(:,:,z)=b*GDCTi(:,:,z);
        Gdi(:,:,z)=c(:,:,z)*b;
  end
  %Gdi =uint8(Gdi(:,:,z));
   %%%%%%%%%%%%%%%%%%%%%%%%%%%%ùùùùùùùùùùùùùùùùùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù
  p=1;
  pas_sbloc=8;
  for i=1:pas_sbloc:lg
     for j=1:pas_sbloc:cg
       C(i:pas_sbloc+i-1,j:pas_sbloc+j-1)=Gdi(:,:,p);
        p=p+1;
     end
  end
  if  ng==1
      Rh=C;
  elseif ng==2
      Gh=C;
  else
      Bh=C;
  end 
  end
  figure(2);
  A=cat(3,Rh,Gh,Bh);
  imshow(uint8(A));

[Walter Roberson]

In what manner is it broken? Do you get an error message? How does the output differ from your expectations?