photomolo and jpegcom release notes

photomolo 1.0
generate thumbnails and HTML navigation for a collection of digital photographs in JPEG format
jpegcom 1.0
read or write the comments of JPEG images

Copyright information

The 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 jpegcom utility was written from the scratch by Marko Mäkelä in 2003. The following statement applies to both 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.

Table of Contents

1 Motivation
2 Writing image comments with jpegcom
3 Creating thumbnails and HTML navigation with photomolo
4 Frequently Asked Questions
4.1 Why yet another image gallery program?
4.2 Why is there no graphical user interface?
4.3 Where can I obtain the software?

1 Motivation

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.

2 Writing image comments with jpegcom

In 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:

  1. invoke jpegcom *.jpg > control.txt to produce a template for commenting and renaming or copying the files
  2. view the images *.jpg and add suitable comments to control.txt
  3. invoke jpegcom < control.txt to embed the comments in the images

For details, please refer to the manual page or read the comments that jpegcom writes in the beginning of the control file.

3 Creating thumbnails and HTML navigation with photomolo

If 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.

4 Frequently Asked Questions

4.1 Why yet another image gallery program?

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:

Small size
Existing packages written in Perl, PHP, Python, Java or other languages depend on many libraries and programs that might not be installed everywhere. Does a simple utility really require several megabytes of software?
Compliance to standards
The output produced by the tool must be valid HTML and CSS. It must work both with present and with future browsers, so that the output can be recorded on permanent media, such as CD-R.
Portability
The software must be written in a standardised language (C, ISO 9899:1999) for a standardised run-time environment (POSIX, IEEE Std 1003.1-2001), so that it can easily be ported to contemporary and future computer systems. Small size and independence of large software packages helps here.

4.2 Why is there no graphical user interface?

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.

4.3 Where can I obtain the software?

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.

Marko Mäkelä