function matrix(m, n) {
  var cols=m;
  var rows=m;
  var half=cols/2;
  for (i=0; i<rows; i++) {
    document.write('<tr>');
    for (j=0; j<cols; j++) {
      var k=255-i*j;
      var i1=16*i;
      var j1=16*j;
      var l=rows-i-1;
      if (i == j || l == j || i == j-half || i == j+half || l == j-half || l == j+half) {
        i1=255-i1;
        j1=255-j1;
        k=255-k;
      }
      var s="\"#"+bytehex(k)+bytehex(i1)+bytehex(j1)+"\"";
      if (n == 1)
        document.write('<td bgcolor=' + s + '>' + '&nbsp;&nbsp;' + '</td>');
      else
        document.write('<td bgcolor=' + s + '>' + '&nbsp;<br />&nbsp;' + '</td>');
    }
    document.write('</tr>');
  }
}