photomolo and jpegcom release notesThe photomolo utility was written from the scratch by
Marko Mäkelä in 2003. The thumbnail images are decompressed and
compressed with libjpeg from the IJG, and the scaling
algorithm has been adapted from pnmscale by
Jef Poskanzer.
The exifiron utility was written from the scratch by
Marko Mäkelä in 2003. The algorithms for lossless JPEG image
transformations have been adapted from jpegtran of the IJG, written by Thomas
G. Lane and Guido Vollbeding, and JPEG files are read and written with
libjpeg from the IJG.
The jpegcom utility was written from the scratch by
Marko Mäkelä in 2003. The following statement applies to all three
utilities:
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose. See the GNU General Public License for more details.
exifironjpegcomphotomoloimage galleryprogram?
If you have a digital camera, you probably have a large amount of
JPEG files
that you would like to publish as a photo album
on a CD-R or on the World Wide
Web.
Simply copying the image files is not adequate. Transferring and decompressing a high-resolution JPEG image can consume several seconds, and the images might not even fit in the screen at full resolution. It would be more convenient to preview the files at a lower resolution.
Another possible problem with a large collection of photographs is that you could forget where a particular image was taken, or what exactly is shown in it. Modern digital cameras usually provide some technical information, such as the time when the image was taken, in the time stamp of the file and in EXIF-formatted JPEG files.
Most file formats for digital pictures offer a possibility to embed textual comments in the files. JPEG is no exception. The documentation or metadata can make a much better browsing experience and enable many possibilities for searching images.
exifironContemporary digital cameras compress images with the JPEG method and store them in EXIF format, which is JFIF extended with a TIFF-formatted APP0 marker that contains metadata, such as camera settings and a thumbnail image.
It is possible to reduce the size of typical image files by five to ten per cent by removing the thumbnail image and by transforming the image data (DCT coefficients) from baseline JPEG to optimised progressive JPEG. These operations do not lose any information: the bitmap representation of the image is unaffected, and the thumbnail image can be reconstructed from the image data.
The EXIF block contains an Orientation tag that has eight possible values, indicating how the image data has been mirrored or rotated. Most JPEG image tools ignore this information. Thus, in order to avoid compatibility problems with EXIF-ignorant viewers, the image data should be flipped and rotated according to the Orientation information.
Last but not least, the EXIF block contains timestamps that indicate when the photograph was taken. In case the timestamp of the image file in the host file system does not reflect the time when the photograph was taken, the information can be restored from the EXIF block.
The exifiron program assists in all these tasks. It
corrects the orientation of images—either automatically
according to Orientation tags or as instructed by command line
switches. It can remove thumbnail images and convert the image data
between the baseline and progressive formats.
Typical usage scenarios of exifiron are as follows:
exifiron *.jpg*.jpg and set the time stamps from the
DateTime tags if available.exifiron -r 1.jpg 2.jpg1.jpg 2.jpg
counterclockwise by 90 degrees. The -r and
-R flags are useful for processing portrait images.jpegcomIn JPEG images, textual comments can be embedded in the COM marker. The file may contain multiple such markers.
Not all utilities for creating or viewing JPEG images allow
comments to be written. Enter jpegcom, a utility that
allows you to edit image comments with the help of your favourite
image viewer and text editor.
Because jpegcom was designed to be as simple and
portable as possible, it lacks a graphical user interface. Instead,
the tool is invoked from the command line. Typical usage is as
follows:
jpegcom *.jpg > control.txt to produce
a template for commenting and renaming or copying the files*.jpg and add suitable comments
to control.txtjpegcom < control.txt to embed the comments
in the imagesFor details, please refer to the manual page or read the comments
that jpegcom writes in the beginning of the control
file.
photomoloIf the images have been divided into subdirectories of no more than
a few dozen images, photomolo can create an efficient set
of HTML
documents for navigation. In each subdirectory containing the
full-resolution images, photomolo creates one
subdirectory for each selected thumbnail type. The thumbnail images
and and the HTML
documents will be written in these directories.
For instance, the command photomolo -T .8/s8 -T .120/h120 -T
.240/h240 images traverses the directory tree
images and creates three types of thumbnail images:
shrunk to an eighth of the original resolution (in subdirectories
named .8), or to 120 or 240 pixels of vertical resolution
(.120 and .240). You probably want to
create a file images/index.html that links to
images/.8/index.html,
images/.120/index.html, and
images/.240/index.html.
For future reference, you may want to write the
photomolo command in a shell script or a batch file.
Subsequent runs of the command will be much faster, since thumbnail
images will only be generated if they do not exist or the timestamps
do not match.
For more information, please refer to the manual page or invoke
photomolo -h.
image galleryprogram?
There are many programs that generate HTML for browsing digital
photographs. photomolo was written, because its author
was unsatisfied with the existing software. The following design
goals were set:
jpegcom does not depend on any external libraries.exifiron and photomolo depend on the
portable libjpeg library from the IJG.Graphical interfaces have not been standardised. If a graphical interface was developed, it would have to be adapted and tested on each of the currently available systems, and it might not work on future systems.
Also, a textual interface can be more powerful and flexible, since text files can be processed and generated with a large variety of programs and programming languages.
The primary distribution site is http://www.funet.fi/pub/sci/graphics/packages/photomolo/.
The programs are freely available under the conditions of the GNU General Public License as C source code for all platforms and as executables for Microsoft Win32.