use strict;
use warnings qw( all );

my @binimage = ( "\x00", "\x00", "\x00", "\x00", "\x00", "\x90" );
my $nextrow = 5;
my $col = 0;
my $subcol = 0;

for my $index (0..5) {
    my $thisrow = $nextrow - $index;
    print "processing row/column/bit $thisrow/$col/$subcol: " . substr($binimage[$thisrow], $col, 1) . "\n";

    printf ("Incoming byte is %d/%x/%8b/%s.  Test bitmask is %d/%x/%8b/%s.\n",
        substr($binimage[$thisrow], $col, 1),
        substr($binimage[$thisrow], $col, 1),
        substr($binimage[$thisrow], $col, 1),
        unpack('B8',substr($binimage[$thisrow], $col, 1)),
        2**(7-$subcol),
        2**(7-$subcol),
        2**(7-$subcol),
        unpack('B8', 2**(7-$subcol)));

    printf "%s\n", ((substr($binimage[$thisrow], $col, 1)) & 2**(7-$subcol))? "1" : "0";
}