PNG (Portable Network Graphics) Home Site

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd"> <HTML> <HEAD> <TITLE>PNG (Portable Network Graphics) Home Site</TITLE> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">  <STYLE TYPE="text/css"> P { margin-bottom: 0em } UL { margin-bottom: 0em; margin-top: 0em; } LI { padding: 0px 0px 0px 0px; margin: 0px 0px 0px 0px; list-style: disc; } </STYLE> <LINK REV="made" HREF="http://gregroelofs.com/greg_contact.html">  </HEAD> <BODY BGCOLOR="#000000" TEXT="#eeeeee" LINK="#ffff00" VLINK="#ff9922"> <TABLE WIDTH="100%" BORDER=0 CELLPADDING=5> <TR BGCOLOR="#007000"> <TD ALIGN="center" VALIGN="middle"> <A HREF="png-sitemap.html#info"> General Information</A> </TD> <TD ALIGN="center" VALIGN="middle"> <A HREF="png-sitemap.html#apps"> Applications</A> </TD> <TD ALIGN="center" VALIGN="middle"> <A HREF="png-sitemap.html#programming"> Programming Resources</A> </TD> <TD ALIGN="center" VALIGN="middle"> <A HREF="png-sitemap.html#images"> Images</A> </TD> <TD ALIGN="center" VALIGN="middle"> <A HREF="png-sitemap.html#animation"> Animation</A> </TD> </TR> </TABLE>   If you're using a Windows version of Netscape Navigator and want to print this page (and still be able to read it), click on the png-printable link at the very bottom of this page.  <CENTER>  <A HREF="pngpic2.html"> <IMG WIDTH=800 HEIGHT=600 BORDER=0 SRC="img_png/pnglogo--povray-3.7--black826--800x600.png" ALT="[PNG: 800x600 colored-balls logo]"></A>  <A HREF="pngfaq.html#jpeg-logo">FAQ</A> </CENTER> <CENTER> <H1 ALIGN="center"> Portable Network Graphics </H1> <H3 ALIGN="center">  An Open, Extensible Image Format with Lossless Compression </H3> <H4 ALIGN="center"> (Not Related to Papua New Guinea, the Pawnee National Grassland, the Professional Numismatists Guild or the "Pack 'N' Go" format)    </H4> </CENTER> Welcome to the PNG Home Site, maintained by <A HREF="http://gregroelofs.com/" >Greg Roelofs</A>. 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 programming code related to the 29-year-old PNG image format.  <DIV ALIGN="center"> <FORM METHOD=get ACTION="http://search.yahoo.com/search" STYLE="border:1px solid #777; background-color: #000000; padding:5px; width:550px; text-align:center;">  <A HREF="http://search.yahoo.com/"><IMG ALT="[Yahoo! Search]" SRC="images/yahoo-search-black.png" WIDTH=105 HEIGHT=34 ALIGN="middle" BORDER=0></A> <INPUT TYPE="text" NAME="p" SIZE=40> <INPUT TYPE="hidden" NAME="fr" VALUE="yscpb"> <INPUT TYPE="submit" VALUE="Search"> <INPUT TYPE="radio" NAME="vs" ID="ysvs1" STYLE="vertical-align: middle" VALUE="www.libpng.org" CHECKED><LABEL FOR=ysvs1 STYLE="margin-right: 75px;">Search this site</LABEL>   <INPUT TYPE="radio" NAME="vs" ID="ysvs0" STYLE="vertical-align: middle" VALUE=""><LABEL FOR=ysvs0>Search the web</LABEL> </FORM> </DIV> <HR> <DL> <DD> <A HREF="libpng.html"><IMG ALIGN="right" WIDTH=91 HEIGHT=41 SRC="img_png/libpng.png" ALT="[download libpng]"></A> Canonical URL: <A HREF="http://www.libpng.org/pub/png/" >http://www.libpng.org/pub/png/</A> (California, USA)   </DD>                                                                     </UL> </DD> </DL> Note that the PNG home site has moved four times since 1995 (though the URL has changed only three times, and hopefully never again). The current site is hosted by the excellent folks at <A HREF="https://sourceforge.net/" >SourceForge</A>.   <A HREF="http://sourceforge.net/projects/png-mng"><IMG WIDTH=80 HEIGHT=15 SRC="http://sflogo.sourceforge.net/sflogo.php?group_id=32355&type=9" ALT="[primary site hosted by SourceForge]" BORDER=0 ></A>          <HR> <CENTER> <TABLE BORDER=0 CELLPADDING=5> <TR BGCOLOR="#000080"> <TD> PNG Site Layout </TD> </TR> </TABLE> </CENTER> The PNG web site is organized into four basic categories of information (blue and white headings below), not counting the separate <A HREF= "http://www.libpng.org/pub/mng/">MNG site</A> (covering PNG's animated and lossy cousins). A <A HREF="png-sitemap.html">complete site map</A> to the 110+ pages is available, but the basics are summarized here.   The <A HREF="#history">informal history</A> below is worth reading both for general background and for a summary of PNG's main features, but most non-programmers will probably find the <A HREF="pngintro.html">basic introduction</A>, the <A HREF="pngfaq.html">FAQ</A>, and perhaps the <A HREF="pnghist.html">longer history</A>  to be of the greatest interest and utility. The <A HREF="pngapps.html">PNG-supporting application lists</A>, on the other hand, are no longer particularly important (or maintained), insofar as virtually every image-related application has supported PNG natively--and well--for more than a decade. They too are now historical in nature. <IMG HEIGHT=16 WIDTH=16 ALIGN="bottom" SRC="images/smile.happy.png" ALT=":-)">  <A NAME="info"></A> <TABLE BORDER=0 CELLPADDING=5> <TR BGCOLOR="#000080"> <TD> PNG General Information </TD> </TR> </TABLE> <DL> <DD> <IMG WIDTH=10 HEIGHT=10 SRC="images/li_purple.png" ALT=" * "> <A HREF="pngintro.html">A Basic Introduction to PNG Features</A> (recommended for new visitors) </DD> <DD> <IMG WIDTH=10 HEIGHT=10 SRC="images/li_purple.png" ALT=" * "> <A HREF="pngstatus.html">Current Status of PNG</A> (recommended for new visitors) </DD> <DD> <IMG WIDTH=10 HEIGHT=10 SRC="images/li_blupur.png" ALT=" * "> <A HREF="pngfaq.html">Frequently Asked Questions</A> (recommended for new visitors) </DD> <DD> <IMG WIDTH=10 HEIGHT=10 SRC="images/li_blue.png" ALT=" * "> <A HREF="./#history">An Informal History of PNG</A> (and a <A HREF="pnghist.html">More Detailed History</A>) </DD> <DD> <IMG WIDTH=10 HEIGHT=10 SRC="images/li_medblue.png" ALT=" * "> <A HREF="pngnews.html">News of the PNG Development Group</A> </DD> <DD> <IMG WIDTH=10 HEIGHT=10 SRC="images/li_ltblue.png" ALT=" * "> <A HREF="pngmisc.html#lists">Links to Other PNG Resources</A> (includes mailing lists) </DD> <DD> <A HREF="book/"><IMG ALIGN="right" WIDTH=50 HEIGHT=66 SRC="img_png/pngbook-cover-micro.png" ALT="[cover]"></A> <IMG WIDTH=10 HEIGHT=10 SRC="images/li_aqua.png" ALT=" * "> <A HREF="pngdocs.html">PNG Technical Documentation</A> <UL TYPE="disc"> <LI><A HREF= "spec/" >PNG Specification and Extensions</A> (<A HREF="spec/iso/" >latest version</A>) <LI><A HREF= "http://www.zlib.net/zlib_docs.html" >zlib Technical Documentation</A> <LI><A HREF="http://www.libpng.org/pub/mng/mngdocs.html" >MNG / JNG Technical Documentation</A> </UL> </DD> <DD> <IMG WIDTH=10 HEIGHT=10 SRC="images/li_aqua.png" ALT=" * "> <A HREF="pngbook.html">PNG: The Definitive Guide and Related Books</A> </DD> </DL>  <A NAME="apps"></A> <TABLE BORDER=0 CELLPADDING=5> <TR BGCOLOR="#000080"> <TD> PNG-Supporting Applications </TD> </TR> </TABLE> <DL> <DD> <IMG WIDTH=10 HEIGHT=10 SRC="images/li_green.png" ALT=" * "> <A HREF="pngapps.html">Applications with PNG Support</A> <UL TYPE="disc"> <LI><A HREF="pngapbr.html">Browsers</A> <LI><A HREF="pngapvw.html">Image Viewers</A> <LI><A HREF="pngaped.html">Image Editors</A> <LI><A HREF="pngapcv.html">Image Converters</A> <LI><A HREF="pngap3d.html">3D Applications</A> (also <A HREF="pngvrml.html">VRML Browsers</A>) <LI><A HREF="pngapgm.html">Games / Entertainment</A> <LI><A HREF="pngapof.html">Office / Business Applications</A> <LI><A HREF="pngapsc.html">Scientific / Graphing Applications</A> <LI><A HREF="pngapmi.html">Miscellaneous Applications</A> </UL> </DD> <DD> <IMG WIDTH=10 HEIGHT=10 SRC="images/li_yelgrn.png" ALT=" * "> <A HREF="pnghw.html">Hardware with PNG Support</A> </DD> </DL>  <A NAME="programming"></A> <TABLE BORDER=0 CELLPADDING=5> <TR BGCOLOR="#000080"> <TD> PNG Programming Resources </TD> </TR> </TABLE> <DL> <DD> <IMG WIDTH=10 HEIGHT=10 SRC="images/li_yellow.png" ALT=" * "> PNG Programming Information: <UL TYPE="disc"> <LI><A HREF="pngaptk.html">PNG-supporting Libraries and Toolkits</A> <UL TYPE="disc"> <LI><A HREF="libpng.html">libpng home page</A> <LI><A HREF="http://www.zlib.net/" >zlib home page</A>  <LI><A HREF="http://www.libmng.com/" >libmng home page</A> </UL> <LI><A HREF="pngcode.html">PNG Source Code</A> </UL> </DD> </DL>  <A NAME="images"></A> <TABLE BORDER=0 CELLPADDING=5> <TR BGCOLOR="#000080"> <TD> PNG Images </TD> </TR> </TABLE> <DL> <DD> <A HREF="pngs-img.html"><IMG ALIGN="right" WIDTH=60 HEIGHT=94 SRC="img_png/pngs-img-ie5mac-micro.png" ALT="[images]"></A> <IMG WIDTH=10 HEIGHT=10 SRC="images/li_orange3.png" ALT=" * "> PNG Images: <UL TYPE="disc"> <LI><A HREF="pngsuite.html" >Willem van Schaik's Test Suite of PNG Icons</A> <LI><A HREF="png-textures.html" >Greg's Test Suite of PNG Textures for VRML</A> <LI><A HREF="pngpic2.html" >Ray-traced PNG Interlacing Demo</A> (also <A HREF="pngpics.html">JPEG version</A>) <LI><A HREF="pngs-img.html" >Miscellaneous Transparent PNGs using IMG Tags</A> (includes links to screenshots) <LI><A HREF="pngs.html" >Miscellaneous Transparent PNGs using OBJECT Tags</A> (also <A HREF="pngs-strict.html">strict HTML 4.0 version</A>) <LI><A HREF="png-rgba32.html" >Miscellaneous 32-bit RGBA PNGs</A> <LI>Photographic PNGs with Alpha Transparency: <UL TYPE="disc"> <LI><A HREF="png-IceAlpha.html">Icicles</A> <LI><A HREF="png-RedbrushAlpha.html">Redbrush flower</A> (Ohia Lehua) <LI><A HREF="png-MagnoliaAlpha.html">Magnolia tree</A> <LI><A HREF="png-OwlAlpha.html">Horned Owl</A> </UL> <LI><A HREF="png-gammatest.html" >Browser Gamma-Correction Test</A>  <LI><A HREF="png-colortest.html" >Browser Color-Correction Test</A>   </UL> </DD>  <DD> <IMG WIDTH=10 HEIGHT=10 SRC="images/li_red.png" ALT=" * "> <A HREF="pngmisc.html#images">Links to Other PNG Resources</A> (includes pointers to more PNG images) </DD> </DL>  <A NAME="animation"></A> <TABLE BORDER=0 CELLPADDING=5> <TR BGCOLOR="#000080"> <TD> PNG Animation </TD> </TR> </TABLE> <DL> <DD> <IMG WIDTH=10 HEIGHT=10 SRC="images/li_magenta.png" ALT=" * "> <A HREF="http://www.libpng.org/pub/mng/">Multiple-image Network Graphics (MNG) Home Site</A> (includes JNG: JPEG with alpha-transparency) </DD> </DL> <A NAME="history"></A> <HR> <H3> <IMG WIDTH=32 HEIGHT=24 SRC="img_png/pnglogo-blk-tiny.png" ALT="[PNG icon]"> What It Be (An Informal History) </H3> 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 bitmapped (raster) images on computers. Unofficially its acronym stands for <IMG ALIGN="right" WIDTH=200 HEIGHT=37 SRC="img_png/png01aaaa-crb.png" ALT="[ </gif><png> ]"> "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. <BLOCKQUOTE> (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.)    </BLOCKQUOTE> 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 <A HREF="pngintro.html">spiffier features</A> include: <UL> <LI>unambiguous pronunciation (ooo, baby!) <LI>multiple CRCs so that file integrity can be checked without viewing <LI>ultra-clever magic signature that can detect the most common types of file corruption <LI>better compression than GIF, typically 5% to 25% (but often 40% or 50% better on tiny images) <LI>non-patented (you betcha!), completely lossless compression <LI><A HREF="pngpics.html">majorly gnarly two-dimensional interlacing scheme</A> <LI>1-, 2-, 4- and 8-bit palette support (like GIF) <LI>1-, 2-, 4-, 8- and 16-bit grayscale support <LI>8- and 16-bit-per-sample (that is, 24- and 48-bit) truecolor support <LI>full alpha transparency in 8- and 16-bit modes, not just simple on-off transparency like GIF <LI>"palette-alpha" mode, effectively transforming normal RGB palette into RGBA <LI>gamma correction for cross-platform "brightness" control <LI>color correction for cross-platform, precision color <LI>both compressed and uncompressed text chunks for copyright and other info <LI>full Year 2000 (Y2K) support, and then some (good for at least 63 millenia! yowza!) <LI><A HREF="libpng.html">free and complete reference implementation with full source code</A> </UL> Not exactly spiffy, but worth mentioning anyway: <UL> <LI>officially registered Internet media ("MIME") type: image/png </UL> 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 <A HREF="pngintro.html">Basic Introduction to PNG Features</A>. Those who want all of the gory details can either find a library with the <A HREF="http://www.ddj.com/ddj/1995/1995.07/">July 1995 issue</A> of <A HREF="http://www.ddj.com/">Dr. Dobb's Journal</A> and read <A HREF="http://www.piclab.com/">Lee Crocker</A>'s PNG article; read a copy of Greg's O'Reilly book,  <A HREF="pngbook.html">PNG: The Definitive Guide</A>; or else go read the full <A HREF="spec/">Portable Network Graphics  Specification</A>, a reasonably concise <A HREF="http://www.w3.org/">W3C</A> 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 <A HREF="pngdocs.html">PNG documentation page</A> for links to plain ASCII, PostScript (US letter-size) and PDF versions, and see the W3C's <A HREF="http://www.w3.org/Graphics/PNG/">PNG page</A> and official <A HREF="http://www.w3.org/Press/PNG-PR.en.html">press release</A> for links to related documentation on gamma and color correction. Note that the PNG specification was updated to version 1.1 on New Year's Eve 1998 (that is, 31 December 1998). It included 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!). A second, more minor update (version 1.2) was released in August 1999; its only change was the addition of the iTXt chunk (international text).   In addition, PNG began the long process of international standardization* in 1999 (see the <A HREF="png1999.html">10 May 1999</A> news item for details), thanks largely to its inclusion in <A HREF= "http://www.web3d.org/x3d/specifications/vrml/ISO-IEC-14772-VRML97/" >VRML97</A>. It finally completed that process and became the joint ISO/IEC standard 15948:2004  nearly five years later (see the <A HREF="png2004.html">3 March 2004</A> news item), a few months after it was also rereleased by the W3C (with identical content) as their "<A HREF= "http://www.w3.org/TR/2003/REC-PNG-20031110/">PNG Second Edition</A>" Recommendation. <BLOCKQUOTE> *PNG was already part of the  <A HREF="http://www.mheg.org/users/mheg/archives/doc/MHEG-5_Profile_Issue_1.pdf" >UK profile</A> for MHEG-5 on digital terrestrial television; MHEG-5 is the international standard for a next-generation teletext system that shares a number of features with HTML. PNG is also used in MHP, the Java-based <A HREF= "http://www.mhp.org/html_index.html">Multimedia Home Platform</A> for digital video systems, and was included in HAVi, the somewhat defunct <A HREF= "http://www.havi.org/">Home Audio-Video Interoperability</A> standard for 1394-based home networking. </BLOCKQUOTE> And the design of the multi-image extension to PNG known as <A HREF= "http://www.libpng.org/pub/mng/">MNG</A> is officially complete (version 1.0 of the MNG specification was released on 31 January 2001), with quite a number of applications available and a <A HREF="http://www.libmng.com/">free reference library</A>, too.  By now you're undoubtedly drooling over such an incredibly well-designed image format and wondering where you can find <A HREF="pngapps.html" >applications</A> or <A HREF="pngcode.html">programming tools</A> that support it. Well, wonder no further! Greg aims to please. <CENTER> <H5 ALIGN="center">  <A HREF="pngapps.html"><IMG WIDTH=98 HEIGHT=31 BORDER=0 SRC="img_png/pngnow.png" ALT="[PNG (apps) now!]"></A> </H5> </CENTER> <TABLE WIDTH="100%" BORDER=0 CELLPADDING=5> <TR BGCOLOR="#007000"> <TD ALIGN="center" VALIGN="middle"> <A HREF="png-sitemap.html#info"> General Information</A> </TD> <TD ALIGN="center" VALIGN="middle"> <A HREF="png-sitemap.html#apps"> Applications</A> </TD> <TD ALIGN="center" VALIGN="middle"> <A HREF="png-sitemap.html#programming"> Programming Resources</A> </TD> <TD ALIGN="center" VALIGN="middle"> <A HREF="png-sitemap.html#images"> Images</A> </TD> <TD ALIGN="center" VALIGN="middle"> <A HREF="png-sitemap.html#animation"> Animation</A> </TD> </TR> </TABLE> <A HREF= "http://validator.w3.org/check?uri=http%3A%2F%2Fwww.libpng.org%2Fpub%2Fpng%2F" ><IMG HEIGHT=31 WIDTH=88 BORDER=0 ALIGN="right" SRC="images/vh40.png" ALT="[Valid HTML 4.0]"></A> Last modified 27 January 2024,  you betcha.  Copyright © 1995-2024 <A HREF="http://gregroelofs.com/">Greg Roelofs</A> (<A HREF="http://gregroelofs.com/greg_contact.html">contact</A>).         <A HREF="png-printable.html">png-printable.html</A>  </BODY> </HTML>

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PNG (Portable Network Graphics) Home Site