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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, 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 horizontal 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 otherwise. Note that it is possible to include thumbnails in for-mats formats
              mats 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 contain-ing containing
              ing 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 formats 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)]]


       ::jpeg::exifKeys
              Returns  a list of the EXIF keys which are currently understood.  There may be keys present in
              getExif data that are not understood.  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 application 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::addComment 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  (usu-ally (usually
              ally  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  imple-mented implemented
       mented

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




jpeg                                                0.3.5                                            jpeg(n)