convert fb's raw data to png

if you want to check your last display from fbdev,
you can "cat /dev/fb0 > fb0.raw" and review it by converting png file.

#!/usr/bin/perl -w

$w = shift || 240;
$h = shift || 320;
$pixels = $w * $h;

open OUT, "|pnmtopng" or die "Can't pipe pnmtopng: $!\n";

printf OUT "P6%d %d\n255\n", $w, $h;

while ((read STDIN, $raw, 2) and $pixels--) {
  $short = unpack('S', $raw);
  print OUT pack("C3",
     ($short & 0xf800) >> 8,
     ($short & 0x7e0) >> 3,
     ($short & 0x1f) << 3);
}

close OUT;