jpeg(n)                     JPEG image manipulation                    jpeg(n)



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NAME
       jpeg - JPEG querying and manipulation of meta data

SYNOPSIS
       package require Tcl  8.2

       package require jpeg  ?0.4.0?

       ::jpeg::isJPEG file

       ::jpeg::imageInfo file

       ::jpeg::dimensions file

       ::jpeg::getThumbnail file

       ::jpeg::getExif file ?section?

       ::jpeg::getExifFromChannel channel ?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
              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::getExifFromChannel channel ?section?
              This command is as per ::jpeg::getExif except that it uses a
              previously opened channel.  channel should be a seekable channel
              and section is as described in the documentation of
              ::jpeg::getExif Note: the jpeg parser expects that the start of
              the channel is the start of the image data. If working with an
              image embedded in a container file format it may be necessary to
              read the jpeg data into a temporary container: either a
              temporary file or a memory channel.

       ::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 (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
       bugs and other problems.  Please report such in the category jpeg of
       the Tcllib SF Trackers
       [http://sourceforge.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>
       Copyright (c) 2011, Code: Pat Thoyts <patthoyts@users.sourceforge.net>




jpeg                                 0.4.0                             jpeg(n)
