# untested
my $im = Imager->new(xsize=>$width, ysize=>$height);
my $per_line = $width * 4;

# adjust the data to the format setscanline() takes
$nfr =~ s/(.)(.)(.)/$3$2$1\xFF/gs;

# paint it
for my $y (0..$height-1) {
  $im->setscanline(y=>$y, pixels => 
      substr($nfr, $y * per_line, $per_line));
}