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Jean-loup's home page

Hi! I'm Jean-loup Gailly. Here are some of the things I'm interested in.

a zip

Data compression

gzip I am the author of gzip, a data compression program relatively popular on the Internet, designed to replace compress. Mark Adler wrote the decompression code. For this work Mark and I received the Usenix 2009 STUG award (video).

zip I have written the compression code of the portable archiver zip of the Info-Zip group. zip and unzip are compatible with the pkzip archiver.

The zip compression code is used in the PGP encryption program.

zlib In collaboration with Mark Adler, I have written the zlib, data compression library, which lets you compress or decompress data in memory or read and write files in the gzip format.

The data format used by the zlib library is described by RFCs (Request for Comments) 1950 (zlib format) and 1951 (deflate format). This format is used in particular in the PNG image format. A closely related format has been adopted for one of the PPP compression protocols. zlib is used in many other applications (Apache, PGP, Java, Microsoft Office...).

The zlib authors can be reached by e-mail at . Please read the FAQ and the manual before asking us for help. We are getting too many questions which already have an answer in the zlib documentation.

book I am a coauthor of Mark Nelson's book The Data Compression Book; I wrote the chapter on fractal image compression. A short introduction to fractal compression is also given here.

The sources of my fractal compression program are here (tar.gz or zip format).

question Finally, I created the FAQ (Frequently Asked Questions) of the comp.compression newsgroup. (Also available by ftp.) In particular if you wonder how to extract a file in format X on a system Y, please check the FAQ before posting or mailing.



I have a strong interest in computer security. See my specific security page about this.



Before the release of gzip, I studied a lot of patents on data compression to make sure that my implementation avoided all of them. See section 8 of the comp.compression FAQ for a small subset (several dozen) of all patents I've looked at.

During my search, I found two interesting patents on a process which is mathematically impossible: compression of random data. This is somewhat equivalent to patents on perpetual motion machines. Check here for a short analysis of these two patents.

at sea


pulsar In 1978, I published together with James Lequeux, my professor at the Ecole Polytechnique, a paper on the galactic distribution of pulsars (Astronomy and Astrophysics, 70, L15-L18, 1978). A pulsar is not visually appealing, so have a look instead at Cygnus Loop which contains a pulsar. The Crab Nebula results from the explosion of a supernova in 1054; it houses a pulsar in its center.

In 1979 and 1980, I studied the stratospheric turbulence within the Service d'Aéronomie du CNRS, by attaching a very sensitive anemometer under a stratospheric balloon filled with hydrogen.

From 1981 to 1989 I participated in the construction of code generators and real-time systems for the Ada language within Alsys. I was a member of the Ada language design team.

From 1990 to 1995 I was responsible for the real-time executive of the Chorus micro-kernel.

medical imaging From 1996 to 1999 I have been responsible for medical imaging applications within General Electric Medical Systems.

Mandrake From 1999 to 2001 I was CTO of Mandrakesoft, the company producing the Linux Mandrake operating system. I was then interviewed on Slashdot.

Poseidon In June 2001 I joined Vision IQ / Poseidon, a software company specialized in computer vision, as Chief Information Officer and Chief Software Architect.

Business Objects From 2003 to 2006 I led the Release Management Tools team at Business Objects.

Google From 2006 to 2014 I was Tech Lead Manager at Google Switzerland then Google France.


go symbol I am a fan of the game of go (also named WeiChi or WeiQi in China and Baduk in Korea). Visit my go page to see some nice images.

The French newspaper Planete Linux interviewed me for its Oct. 2002 issue. The text and images are here (in French).

Thanks to Zjev Ambagts and Ken Warkentyne for images of go players. Thanks to Bill Chin for some of the clipart used in this page.

write Send your comments to . My PGP key is here. You can call me either Jean-loup or Jean-Loup, but not Jean or Mr. Loup! Smile
Last modification: Mai 2019.
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