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>