


jpeg(n)              JPEG image manipulation              jpeg(n)


______________________________________________________________________________

NAME
       jpeg - JPEG querying and manipulation of meta data

SYNOPSIS
       package require Tcl  8.2

       package require jpeg  ?0.3.5?

       ::jpeg::isJPEG file

       ::jpeg::imageInfo file

       ::jpeg::dimensions file

       ::jpeg::getThumbnail file

       ::jpeg::getExif file ?section?

       ::jpeg::formatExif keys

       ::jpeg::exifKeys

       ::jpeg::removeExif file

       ::jpeg::stripJPEG file

       ::jpeg::getComments file

       ::jpeg::addComment file text...

       ::jpeg::removeComments file

       ::jpeg::replaceComment file text

       ::jpeg::debug file

       ::jpeg::markers channel

_________________________________________________________________

DESCRIPTION
       This  package  provides  commands to query and modify JPEG images. JPEG
       stands for Joint Photography Experts Group and is a  standard  for  the
       lossy   compression  of  photographical  images.  It  is  specified  at
       LINK_HERE.

COMMANDS
       ::jpeg::isJPEG file
              Returns a boolean value indicating if file is a JPEG image.

       ::jpeg::imageInfo file
              Returns  a  dictionary  with  keys  version,  units,   xdensity,



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jpeg(n)              JPEG image manipulation              jpeg(n)


              ydensity,  xthumb,  and  ythumb.  The  values are the associated
              properties of the JPEG image in file.  Throws an error  if  file
              is not a JPEG image.

       ::jpeg::dimensions file
              Returns  the  dimensions of the JPEG file as a list of the hori-
              zontal and vertical pixel count.  Throws an error if file is not
              a JPEG image.

       ::jpeg::getThumbnail file
              This procedure will return the binary thumbnail image data, if a
              JPEG thumbnail is included in file, and the empty string  other-
              wise.  Note that it is possible to include thumbnails in formats
              other than JPEG although that is not common. The  command  finds
              thumbnails  that are encoded in either the JFXX or EXIF segments
              of the JPEG information. If both are present the EXIF  thumbnail
              will  take  precedence.   Throws  an error if file is not a JPEG
              image.

                  set fh [open thumbnail.jpg w+]
                  fconfigure $fh -translation binary -encoding binary
                  puts -nonewline $fh [::jpeg::getThumbnail photo.jpg]
                  close $fh


       ::jpeg::getExif file ?section?
              section must be one of main or thumbnail.  The default is  main.
              Returns  a  dictionary  containing  the EXIF information for the
              specified section.  For example:


                  set exif {
                   Make     Canon
                   Model    {Canon DIGITAL IXUS}
                   DateTime {2001:06:09 15:17:32}
                  }

              Throws an error if file is not a JPEG image.

       ::jpeg::formatExif keys
              Takes a list of key-value pairs as returned by getExif and  for-
              mats  many of the values into a more human readable form. As few
              as one key-value may be  passed  in,  the  entire  exif  is  not
              required.

                  foreach {key val} [::jpeg::formatExif [::jpeg::getExif photo.jpg]] {
                      puts "$key: $val"
                  }



                  array set exif [::jpeg::getExif photo.jpg]
                  puts "max f-stop: [::jpeg::formatExif [list MaxAperture $exif(MaxAperture)]]




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jpeg(n)              JPEG image manipulation              jpeg(n)


       ::jpeg::exifKeys
              Returns  a list of the EXIF keys which are currently understood.
              There may be keys present in getExif data that  are  not  under-
              stood.   Those keys will appear in a 4 digit hexadecimal format.

       ::jpeg::removeExif file
              Removes the Exif  data  segment  from  the  specified  file  and
              replaces  it  with  a standard JFIF segment.  Throws an error if
              file is not a JPEG image.

       ::jpeg::stripJPEG file
              Removes all metadata from the JPEG file leaving only the  image.
              This includes comments, EXIF segments, JFXX segments, and appli-
              cation specific segments.  Throws an error if file is not a JPEG
              image.

       ::jpeg::getComments file
              Returns  a  list  containing  all the JPEG comments found in the
              file.  Throws an error if file is not a valid JPEG image.

       ::jpeg::addComment file text...
              Adds one or more plain text comments to the JPEG image in  file.
              Throws an error if file is not a valid JPEG image.

       ::jpeg::removeComments file
              Removes  all  comments from the file specified.  Throws an error
              if file is not a valid JPEG image.

       ::jpeg::replaceComment file text
              Replaces the first comment in the file with the new text.   This
              is merely a shortcut for ::jpeg::removeComments and ::jpeg::add-
              Comment Throws an error if file is not a valid JPEG image.

       ::jpeg::debug file
              Prints everything we know about the given file in a nice format.

       ::jpeg::markers channel
              This  is  an  internal helper command, we document it for use by
              advanced users of the package. The argument channel is  an  open
              file handle positioned at the start of the first marker (usually
              2 bytes). The command returns a list with one element  for  each
              JFIF  marker  found in the file. Each element consists of a list
              of the marker name, its offset in the file, and its length.  The
              offset  points  to  the  beginning of the sections data, not the
              marker itself.  The length is the length of the  data  from  the
              offset listed to the start of the next marker.


LIMITATIONS
       can  only work with files cant write exif data gps exif data not parsed
       makernote data not yet implemented

BUGS, IDEAS, FEEDBACK
       This document, and the package it describes, will  undoubtedly  contain



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jpeg(n)              JPEG image manipulation              jpeg(n)


       bugs  and  other  problems.  Please report such in the category jpeg of
       the         Tcllib         SF         Trackers          [http://source-
       forge.net/tracker/?group_id=12883].   Please  also report any ideas for
       enhancements you may have for either package and/or documentation.

KEYWORDS
       comment, exif, image, jfif, jpeg, thumbnail

CATEGORY
       File formats

COPYRIGHT
       Copyright (c) 2004-2005, Code: Aaron Faupell <afaupell@users.sourceforge.net>
       Copyright (c) 2007, Code:  Andreas Kupries <andreas_kupries@users.sourceforge.net>
       Copyright (c) 2004-2009, Doc:  Andreas Kupries <andreas_kupries@users.sourceforge.net>










































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