jpeg(3tcl) JPEG image manipulation jpeg(3tcl)
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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
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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, yden-
sity, xthumb, and ythumb. The values are the associated proper-
ties 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 im-
age.
set fh [open thumbnail.jpg w+]
fconfigure $fh -translation binary -encoding binary
puts -nonewline $fh [::jpeg::getThumbnail photo.jpg]
close $fh
::jpeg::getExif file ?section?
section must be one of main or thumbnail. The default is main.
Returns a dictionary containing the EXIF information for the
specified section. For example:
set exif {
Make Canon
Model {Canon DIGITAL IXUS}
DateTime {2001:06:09 15:17:32}
}
Throws an error if file is not a JPEG image.
::jpeg::getExifFromChannel channel ?section?
This command is as per ::jpeg::getExif except that it uses a
previously opened channel. channel should be a seekable channel
and section is as described in the documentation of ::jpeg::ge-
tExif.
Note: The jpeg parser expects that the start of the channel is
the start of the image data. If working with an image embedded
in a container file format it may be necessary to read the jpeg
data into a temporary container: either a temporary file or a
memory channel.
Attention: It is the resonsibility of the caller to close the
channel after its use.
::jpeg::formatExif keys
Takes a list of key-value pairs as returned by getExif and for-
mats many of the values into a more human readable form. As few
as one key-value may be passed in, the entire exif is not re-
quired.
foreach {key val} [::jpeg::formatExif [::jpeg::getExif photo.jpg]] {
puts "$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 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 re-
places 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
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.
When proposing code changes, please provide unified diffs, i.e the out-
put of diff -u.
Note further that attachments are strongly preferred over inlined
patches. Attachments can be made by going to the Edit form of the
ticket immediately after its creation, and then using the left-most
button in the secondary navigation bar.
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>
tcllib 0.5 jpeg(3tcl)