Ubuntu Manpage: jpeg - JPEG querying and manipulation of meta data

NAME

       jpeg - JPEG querying and manipulation of meta data

SYNOPSIS

       package require Tcl  8.2

       package require jpeg  ?0.5?

       ::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.

Attention: It is the resonsibility of the caller to close the channel after its
use.

::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   Trackers
       [http://core.tcl.tk/tcllib/reportlist].  Please also report any ideas for enhancements you
       may have for either package and/or documentation.

KEYWORDS

       comment, exif, image, jfif, jpeg, thumbnail

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>