'\"
'\" Generated from file 'jpeg\&.man' by tcllib/doctools with format 'nroff'
'\" 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>
'\"
.TH "jpeg" n 0\&.7 tcllib "JPEG image manipulation"
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.SH NAME
jpeg \- JPEG querying and manipulation of meta data
.SH SYNOPSIS
package require \fBTcl 8\&.5 9\fR
.sp
package require \fBjpeg ?0\&.7?\fR
.sp
\fB::jpeg::isJPEG\fR \fIfile\fR
.sp
\fB::jpeg::imageInfo\fR \fIfile\fR
.sp
\fB::jpeg::dimensions\fR \fIfile\fR
.sp
\fB::jpeg::getThumbnail\fR \fIfile\fR
.sp
\fB::jpeg::getExif\fR \fIfile\fR ?\fIsection\fR?
.sp
\fB::jpeg::getExifFromChannel\fR \fIchannel\fR ?\fIsection\fR?
.sp
\fB::jpeg::formatExif\fR \fIkeys\fR
.sp
\fB::jpeg::exifKeys\fR
.sp
\fB::jpeg::removeExif\fR \fIfile\fR
.sp
\fB::jpeg::stripJPEG\fR \fIfile\fR
.sp
\fB::jpeg::getComments\fR \fIfile\fR
.sp
\fB::jpeg::addComment\fR \fIfile\fR \fItext\fR\&.\&.\&.
.sp
\fB::jpeg::removeComments\fR \fIfile\fR
.sp
\fB::jpeg::replaceComment\fR \fIfile\fR \fItext\fR
.sp
\fB::jpeg::debug\fR \fIfile\fR
.sp
\fB::jpeg::markers\fR \fIchannel\fR
.sp
.BE
.SH DESCRIPTION
.PP
This package provides commands to query and modify JPEG images\&. JPEG
stands for \fIJoint Photography Experts Group\fR and is a standard
for the lossy compression of photographical images\&. It is specified at
\fILINK_HERE\fR\&.
.SH COMMANDS
.TP
\fB::jpeg::isJPEG\fR \fIfile\fR
Returns a boolean value indicating if \fIfile\fR is a
JPEG image\&.
.TP
\fB::jpeg::imageInfo\fR \fIfile\fR
Returns a dictionary with keys \fBversion\fR, \fBunits\fR,
\fBxdensity\fR, \fBydensity\fR, \fBxthumb\fR, and
\fBythumb\fR\&. The values are the associated properties of the JPEG
image in \fIfile\fR\&.
Throws an error if \fIfile\fR is not a JPEG image\&.
.TP
\fB::jpeg::dimensions\fR \fIfile\fR
Returns the dimensions of the JPEG \fIfile\fR as a list of the
horizontal and vertical pixel count\&.
Throws an error if \fIfile\fR is not a JPEG image\&.
.TP
\fB::jpeg::getThumbnail\fR \fIfile\fR
This procedure will return the binary thumbnail image data, if a JPEG
thumbnail is included in \fIfile\fR, 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 \fIfile\fR is not a JPEG image\&.
.CS


    set fh [open thumbnail\&.jpg w+]
    fconfigure $fh -translation binary -encoding binary
    puts -nonewline $fh [::jpeg::getThumbnail photo\&.jpg]
    close $fh

.CE
.TP
\fB::jpeg::getExif\fR \fIfile\fR ?\fIsection\fR?
\fIsection\fR must be one of \fBmain\fR or \fBthumbnail\fR\&.
The default is \fBmain\fR\&.
Returns a dictionary containing the EXIF information for the specified section\&.
For example:
.sp
.CS


    set exif {
	Make     Canon
	Model    {Canon DIGITAL IXUS}
	DateTime {2001:06:09 15:17:32}
    }

.CE
.IP
Throws an error if \fIfile\fR is not a JPEG image\&.
.TP
\fB::jpeg::getExifFromChannel\fR \fIchannel\fR ?\fIsection\fR?
This command is as per \fB::jpeg::getExif\fR except that it uses a
previously opened channel\&.  \fIchannel\fR should be a seekable channel
and \fIsection\fR is as described in the documentation of
\fB::jpeg::getExif\fR\&.
.sp
\fINote\fR: 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\&.
.sp
\fIAttention\fR: It is the resonsibility of the caller to close
the channel after its use\&.
.TP
\fB::jpeg::formatExif\fR \fIkeys\fR
Takes a list of key-value pairs as returned by \fBgetExif\fR 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\&.
.CS


    foreach {key val} [::jpeg::formatExif [::jpeg::getExif photo\&.jpg]] {
        puts "$key: $val"
    }

.CE
.sp
.CS


    array set exif [::jpeg::getExif photo\&.jpg]
    puts "max f-stop: [::jpeg::formatExif [list MaxAperture $exif(MaxAperture)]]

.CE
.TP
\fB::jpeg::exifKeys\fR
Returns a list of the EXIF keys which are currently understood\&.
There may be keys present in \fBgetExif\fR data that are not understood\&.
Those keys will appear in a 4 digit hexadecimal format\&.
.TP
\fB::jpeg::removeExif\fR \fIfile\fR
Removes the Exif data segment from the specified file and replaces
it with a standard JFIF segment\&.
Throws an error if \fIfile\fR is not a JPEG image\&.
.TP
\fB::jpeg::stripJPEG\fR \fIfile\fR
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 \fIfile\fR is not a JPEG image\&.
.TP
\fB::jpeg::getComments\fR \fIfile\fR
Returns a list containing all the JPEG comments found in
the \fIfile\fR\&.
Throws an error if \fIfile\fR is not a valid JPEG image\&.
.TP
\fB::jpeg::addComment\fR \fIfile\fR \fItext\fR\&.\&.\&.
Adds one or more plain \fItext\fR comments to the JPEG image
in \fIfile\fR\&.
Throws an error if \fIfile\fR is not a valid JPEG image\&.
.TP
\fB::jpeg::removeComments\fR \fIfile\fR
Removes all comments from the file specified\&.
Throws an error if \fIfile\fR is not a valid JPEG image\&.
.TP
\fB::jpeg::replaceComment\fR \fIfile\fR \fItext\fR
Replaces the first comment in the file with the new \fItext\fR\&.
This is merely a shortcut for \fB::jpeg::removeComments\fR
and \fB::jpeg::addComment\fR
Throws an error if \fIfile\fR is not a valid JPEG image\&.
.TP
\fB::jpeg::debug\fR \fIfile\fR
Prints everything we know about the given file in a nice format\&.
.TP
\fB::jpeg::markers\fR \fIchannel\fR
This is an internal helper command, we document it for use by advanced
users of the package\&. The argument \fIchannel\fR 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\&.
.PP
.SH LIMITATIONS
can only work with files
cant write exif data
gps exif data not parsed
makernote data not yet implemented
.SH "BUGS, IDEAS, FEEDBACK"
This document, and the package it describes, will undoubtedly contain
bugs and other problems\&.
Please report such in the category \fIjpeg\fR of the
\fITcllib Trackers\fR [http://core\&.tcl\&.tk/tcllib/reportlist]\&.
Please also report any ideas for enhancements you may have for either
package and/or documentation\&.
.PP
When proposing code changes, please provide \fIunified diffs\fR,
i\&.e the output of \fBdiff -u\fR\&.
.PP
Note further that \fIattachments\fR are strongly preferred over
inlined patches\&. Attachments can be made by going to the \fBEdit\fR
form of the ticket immediately after its creation, and then using the
left-most button in the secondary navigation bar\&.
.SH KEYWORDS
comment, exif, image, jfif, jpeg, thumbnail
.SH CATEGORY
File formats
.SH COPYRIGHT
.nf
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>

.fi
