[PNG: 256x192 colored-balls logo]

Portable Network Graphics

A Turbo-Studly* Image Format with Lossless Compression

(Not Related to Papua New Guinea, the Pawnee National Grassland,
the Professional Numismatists Guild or the ``Pack 'N' Go'' format)

Welcome to the PNG Home Site, maintained by Greg Roelofs. Our hero likes to speak of himself in the third person, but don't let that put you off; this is intended to be a mostly serious set of reference pages for locating information, applications and code related to the three-year-old PNG image format.

Canonical URL: http://www.cdrom.com/pub/png/

Automatic mirrors:

Note that the PNG home site has moved twice since 1995; the current site is provided courtesy of the excellent folks at Walnut Creek CD-ROM. Mirror sites have been provided in Texas courtesy of Paul Schmidt, Peter Jensen and Photodex, and in the UK courtesy of Dave Beckett and HENSA Unix. Thanks!

The PNG pages are organized into roughly three dozen separate sections, not counting the separate MNG site. The brief history below is worth reading both for general background and for a summary of PNG's main features, but most people will probably find the Introduction and the list of third-party applications to be of the greatest interest and utility. Additions, updates and corrections are always welcome.

PNG Information

* A Basic Introduction to PNG Features (recommended for new visitors)
* An Informal History of PNG (below)
* A More Detailed History of PNG
* News (and more history) of the PNG Development Group

* PNG Technical Documentation (various formats and mirror sites)
PNG Programming Resources
* PNG Programming Information:
PNG-Supporting Applications
* Applications with PNG Support
* PNG Support in VRML Browsers
PNG Images
* PNG Images:
* Links to Other PNG Resources (includes pointers to more PNG images)
PNG Animations
* Multiple-image Network Graphics Home Site [New!]

[PNG icon] What It Be (An Informal History)

So what is PNG, and why is it worthy of its own home site? PNG (pronounced ``ping'') is the Portable Network Graphics format, a format for storing images on computers. Unofficially its acronym stands for ``PNG's Not GIF.'' PNG was designed to be the successor to the once-popular GIF format, which became decidedly less popular right around New Year's Day 1995 when Unisys and CompuServe suddenly announced that programs implementing GIF would require royalties, because of Unisys' patent on the LZW compression method used in GIF. Since GIF had been showing its age in a number of ways even prior to that, the announcement only catalyzed the development of a new and much-improved replacement format. PNG is the result.

(By the way, despite the implications in some of CompuServe's old press releases and in occasional trade-press articles, PNG's development was not instigated by either CompuServe or the World Wide Web Consortium, nor was it led by them. Individuals from both organizations contributed to the effort, but the PNG development group exists as a separate, Internet-based entity.)

That's only half the story, however; PNG would deserve a home page even if all that had not taken place, just because it's so darned nifty. Yes, it's not every day you come across an image format and say, ``Outraaageous!'' In fact, you may never say that in your entire lifetime (truly a pity), but PNG is still cool. Some of its spiffier features include:

PNG also supports things like suggested quantization, ``smart'' extensibility, a standard color space and lots of other excellent stuff, but let us leave all that aside for now. Those who want a quick explanation of the main features can check out Greg's Introduction to PNG Features. Those who want all of the gory details can either find a library with the July 1995 issue of Dr. Dobb's Journal and read Lee Crocker's PNG article; wait a few months for Greg's upcoming O'Reilly book on PNG; or else go read the full Portable Network Graphics Specification, a reasonably concise W3C Recommendation (the very first one!) that is amazingly well written and understandable. (Greg had no part in the actual writing of it, so he can say things like that.) See the PNG documentation page for links to plain ASCII and PostScript (US letter-size) versions, and see the W3C's PNG page and official press release for links to related documentation on gamma, chromaticity, etc.

Note that the PNG specification was updated to version 1.1 on New Year's Eve (that is, 31 December 1998). It includes new chunks for cross-platform color correction (sRGB and iCCP), a revised and much more sensible description of gamma correction, and a number of other minor improvements and clarifications (all fully backward compatible, of course!). In addition, PNG is now in the early stages of international standardization, thanks largely to its inclusion in the VRML97 standard; it is expected to become a joint ISO/IEC standard by late 1999, if all goes well. And the design of the multi-image extension to PNG known as MNG is basically complete, with a couple of implementations showing considerable promise.

By now you're undoubtedly drooling over such an incredibly well-designed image format and wondering where you can find applications or programming tools that support it. Well, wonder no further! Greg aims to please.

[PNG (apps) now!]

*Commentary from our fun-loving HP contingent, Roger Petersen: ``Try saying Turbo-Studly three times fast after a few beers... My favorite: A Turdly-Stubby New Image format...'' You heard it here first. :-)
Last modified 9 February 1999, you betcha.

Copyright © 1995-1999 Greg Roelofs (newt@pobox.com).