#!/usr/local/bin/perl
## Program name: jpegsize
## Author: Stuart Curtis Lathrop <sclathrop@niitech.com>
## Version: 1.0. July 2000.
## Copyright: This code is placed into the Public Domain under the
##            terms of the GNU Public License. No fee may be charged
##            for its use or distribution.
##
## Kudos to: Rajiv Pant (Betul) <betul@rajiv.com http://rajiv.org>,
##             author of gifsize.pl
##           Jef Poskanzer <jef@acme.com>, author of image_size.c
##           and the Independent JPEG Group for their direction!
##
## THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
## ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
## IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
## ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
## FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
## DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
## OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
## HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
## LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
## OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
## SUCH DAMAGE.
##
## Notes: This script will _not_ handle JPEG redefinition of image size
##        via DNL marker tag.  Files so encoded will either return zero
##        width & height (typically) or will generate a tag error.
##


foreach $jpeg (@ARGV)
{
  $M_SOI  = "\xd8";
  $M_BLK  = "\xff";

  ($width, $height, $type) = jpegsize($jpeg);
  print "$jpeg width = ", $width, ", height = ", $height;
  ($type =~ $M_BLK.$M_SOI) ? print "\n" : print "$jpeg is not a JPEG.\n" ;
}

sub jpegsize
{
  local ($jpeg) = @_ ;
  local ($type, $tag, $marker, $buffer, $lhob, $llob, $blocklen) = ();
  local ($whob, $wlob, $hhob, $hlob, $width, $height) = ();

  ## required jpeg markers
  $M_SOF0 = "\xc0";
  $M_SOF1 = "\xc1";
  $M_SOF2 = "\xc2";
  $M_SOF3 = "\xc3";
  $M_SOI  = "\xd8";
  $M_EOI  = "\xd9";
  $M_SOS  = "\xda";
  $M_BLK  = "\xff";

  open (JPEG, "<".$jpeg) || die "Unable to open $jpeg, $!";
  binmode (JPEG) || die "Cannot read $jpeg in binary mode, $!";
  read (JPEG, $type, 2) || die "Error while reading $jpeg, $!";
  ## check for jpeg file type (start of image) marker
  if (!($type eq $M_BLK.$M_SOI))
  {
    close(JPEG) || die "Error closing $jpeg, $!";
    return ( 0, 0, $type );
  }
  for (;;)
  {
    ## check for block tag
    read (JPEG, $tag, 1) || die "Error while reading $jpeg, $!";
    if ($tag ne $M_BLK)
    {
      print "Error: No start of block marker (0xff) found!\n";
      close(JPEG) || die "Error closing $jpeg, $!";
      return ( 0, 0, $type );
    }
    ## get marker type & block length
    read (JPEG, $marker, 1) || die "Error while reading $jpeg, $!";
    read (JPEG, $lhob, 1) || die "Error while reading $jpeg, $!";
    read (JPEG, $llob, 1) || die "Error while reading $jpeg, $!";
    $blocklen = (ord($lhob) * 256) + ord($llob) - 2;
    ## check for any start of field marker
    if ( $marker ge $M_SOF0 && $marker le $M_SOF3 )
    {
      ## ignore data precision
      read (JPEG, $buffer, 1) || die "Error while reading $jpeg, $!";
      ## read the height and width.
      read (JPEG, $hhob, 1) || die "Error while reading $jpeg, $!";
      read (JPEG, $hlob, 1) || die "Error while reading $jpeg, $!";
      $height = (ord($hhob) * 256) + ord($hlob);
      read (JPEG, $whob, 1) || die "Error while reading $jpeg, $!";
      read (JPEG, $wlob, 1) || die "Error while reading $jpeg, $!";
      $width = (ord($whob) * 256) + ord($wlob);
      # ignore components & rest of file...
      close(JPEG) || die "Error closing $jpeg, $!";
      return ($width, $height, $type);
    }
    else
    {
      if ( $marker eq M_SOS || $marker eq M_EOI )
      {
        ## past header data; size indeterminable
        close(JPEG) || die "Error closing $jpeg, $!";
        return (0, 0, $type);
      }
      ## skip to next marker
      read (JPEG, $buffer, $blocklen);
    }
  }
}