File format conversion software for Seattle FilmWorks products
"Various proprietary file formats incorporating JPEG compression
also exist. We have little or no sympathy for the existence of
these formats. Indeed, one of the original reasons for
developing this free software was to help force convergence on
common, open format standards for JPEG files. Don't use a
proprietary file format!" - The Independent JPEG Group
Seattle FilmWorks (SFW) is a mail order film processor which
offers the option of having your photos digitized when they are
developed. Although this service is very convenient for those
of us who do not want to scan the pictures by hand, SFW returns
the digital pictures to you in one of two proprietary file
formats. They use .sfw format if the pictures are returned on
floppy disk, and .pwp format if they are to be downloaded on the
Since SFW PhotoWorks software, which reads .sfw and .pwp files,
is not available for UNIX, I have written two programs which
convert .sfw and .pwp files to .jpg (JFIF) format, from which
SFW derived these other two formats.
It is interesting to note that PhotoWorks uses code written by
the Independent JPEG Group (IJG). This is done without any sort
of acknowledgement, in violation of the license for the IJG
Neither I (the author) nor this web page are in any way
affiliated with Seattle FilmWorks.
Although I find it annoying that SFW decided to use a
proprietary file format, I am otherwise quite pleased with the
quality of service which I have received from SFW, and would
The following programs will convert Seattle FilmWorks
files back to .jpg (JFIF) format. The programs
sfwjpg and pwpjpg will convert .sfw and .pwp files
to .jpg files. These .jpg files will be flipped
in the vertical direction. To recover your images,
it is recommended that you use the jpegtran program.
This program is included with the Independent JPEG
Group's free JPEG software, which you can find here:
The proper UNIX command line is:
jpegtran -flip vertical < input.jpg > output.jpg
To do more with your pictures, I recommend two very impressive
ImageMagick, by John Cristy, is an image viewing and
manipulation package which is available for most platforms,
including UNIX, VMS, Macintosh, and Microsoft Windows.
Utilities included with ImageMagick can be used to flip jpeg
files (with some loss of quality and/or increase in file size)
if you do not want to compile jpegtran for your platform.
The Gimp, by Peter Mattis,
Spencer Kimball, and many others, is a fully-featured,
extensible image manipulation program with many capabilities
found in similar commercial programs.
Last code update: 9 May 1999
UNIX tar file
- contains all source code, documentation, Solaris and Linux binaries.
- how to use these programs.
- how to compile these programs, and how they work.
- converts a .sfw file to .jpg (JFIF) format.
- extracts .jpg (JFIF) files from a .pwp file.
- Bourne shell script to extract and flip images from a .pwp file.
- does a lossless vertical inversion of a .jpg (JFIF) file.
Use jpegtran instead.
- maintained by Joe Nord.
Last modified: 3 February 2011