% determine possible combinations of tile sizes
clear all, close all, Nx=2880; Ny=2176; px=[]; py=[];
for i=2:sqrt(Nx)
  if mod(Nx,i)==0, px=[px i]; end
end
for i=2:sqrt(Ny)
  if mod(Ny,i)==0, py=[py i]; end
end
n=0;
for i=1:length(px)
  for j=1:length(py)
    n=n+1;
    pnx(n)=px(i);
    snx(n)=Nx/pnx(n);
    pny(n)=py(j);
    sny(n)=Ny/pny(n);
    pnxpny(n)=pnx(n)*pny(n);
  end
end
[pnxpny i]=sort(pnxpny);
pnx=pnx(i); pny=pny(i);
snx=snx(i); sny=sny(i);
[pnxpny' pnx' pny' snx' sny']


     npx*npy         npx         npy         snx         sny
         480          15          32         192          68
         480          30          16          96         136
         510          15          34         192          64
         510          30          17          96         128
         512          16          32         180          68
         512          32          16          90         136
         544          16          34         180          64
         544          32          17          90         128
         576          18          32         160          68
         576          36          16          80         136
         612          18          34         160          64
         612          36          17          80         128
         640          20          32         144          68
         640          40          16          72         136
         680          20          34         144          64
         680          40          17          72         128
         720          45          16          64         136
         765          45          17          64         128
         768          24          32         120          68
         768          48          16          60         136
         816          24          34         120          64
         816          48          17          60         128
         960          30          32          96          68
        1020          30          34          96          64
        1024          32          32          90          68