[x3d-public] Portable Network Graphics (PNG) Third Edition is a Proposed Recommendation

Thu Jun 19 18:11:38 PDT 2025

Wondering if anyone has been using PNG 3, which includes animation capabilities?

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Portable Network Graphics (PNG) Specification (Third Edition)
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W3C Proposed Recommendation 15 May 2025
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This document describes PNG (Portable Network Graphics), an extensible file format for the lossless, portable, well-compressed storage of static and animated raster images. PNG provides a patent-free replacement for GIF and can also replace many common uses of TIFF. Indexed-color, greyscale, and truecolor images are supported, plus an optional alpha channel. Sample depths range from 1 to 16 bits.
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PNG is designed to work well in online viewing applications, such as the World Wide Web, so it is fully streamable with a progressive display option. PNG is robust, providing both full file integrity checking and simple detection of common transmission errors. Also, PNG can store color space data for improved color matching on heterogeneous platforms.
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This specification defines two Internet Media Types, image/png and image/apng.
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https://www.w3.org/TR/png-3
Portable Network Graphics (PNG) Specification (Third Edition)<https://www.w3.org/TR/png-3>
This document describes PNG (Portable Network Graphics), an extensible file format for the lossless, portable, well-compressed storage of static and animated raster images. PNG provides a patent-free replacement for GIF and can also replace many common uses of TIFF. Indexed-color, greyscale, and truecolor images are supported, plus an optional alpha channel.
www.w3.org
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PNG, Third Edition: Implementation Report
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Includes list of implementation libraries and shows web-browser support
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https://w3c.github.io/png/Implementation_Report_3e/
PNG, Third Edition: Implementation Report<https://w3c.github.io/png/Implementation_Report_3e/>
Introduction. This report summarizes the implementation status of PNG, Third Edition at the time of publication: in browsers, image authoring tools, image viewers and other image utilities.. The changes in PNG Third Edition, compared to the Second Edition are divided into new (or newly-standardized) features, substantive changes to existing features, and many editorial corrections and ...
w3c.github.io

Of note there:

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Animated PNG (APNG)[https://w3c.github.io/png/Implementation_Report_3e/img/APNG-Icos4D.png]
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Although proposed in 2007 and widely implemented in browsers between 2009 and 2017, APNG had not been adopted by the ad-hoc group which produced the early PNG specifications. PNG Third Edition retrospectively standardizes this useful extension. APNG has a distinct Internet Media type<https://w3c.github.io/PNG-spec/#image-apng> (MIME type) registered and standardized in PNG Third Edition.

Am expecting X3D implementers and modelers will be interested:

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Implementing and evaluation an ImageTexture capability for 3D texturing as part of (at least 3) X3D players,
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X3DOM https://www.x3dom.org<https://www.x3dom.org/>
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X_ITE      https://create3000.github.io/x_ite
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Castle   https://castle-engine.io/castle-model-viewer

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Listing PNG 3e as a normative requirement in draft X3D 4.1 Architecture, ISO/IEC 19775-1 which in turn affects multiple related international standards for corresponding file formats and programming-language bindings.
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https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/Architecture.html
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Likely deserving upgrading: clause 18 Texturing component, 18.2.2 Texture map image formats
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https://www.web3d.org/specifications/X3Dv4Draft/ISO-IEC19775-1v4.1-CD//Part01/components/texturing.html#TextureMapImageFormats

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Considering potential improved capabilities of PNG 3e in support of 3D Web Interoperability Working Group efforts in Metaverse Standards Forum (MSF)
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https://metaverse-standards.org/domain-groups/3d-web-interoperability<https://metaverse-standards.org/domain-groups/3d-web-interoperability/>

This seems like a major opportunity for X3D modeling and rendering capabilities.

p.s. History lesson learned: yes we can do it!  Following release in 1987, then in the earliest days of the Web, use of Graphics Interchange Format (GIF) images was widespread.   After unfettered adoption for years, Unisys discovered that they had acquired patent rights and announced various plans to start charging royalties.  A number of programmers got together to determine requirements and independently create a "clean room" image format that was unencumbered by patents.  The result turned out to be technically superior in perhaps every respect (including image fidelity, compression, and performance), eventually becoming both a World Wide Web Consortium (W3C) Recommendation and an ISO International Standard.

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Wikipedia, GIF Alternatives: PNG
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Portable Network Graphics<https://en.wikipedia.org/wiki/Portable_Network_Graphics> (PNG) was designed as a replacement for GIF in order to avoid infringement of Unisys' patent on the LZW compression technique.[42]<https://en.wikipedia.org/wiki/GIF#cite_note-PNG-42> PNG offers better compression and more features than GIF,[59]<https://en.wikipedia.org/wiki/GIF#cite_note-png_fea-59> animation being the only significant exception. PNG is more suitable than GIF in instances where true-color imaging and alpha transparency<https://en.wikipedia.org/wiki/Alpha_transparency> are required.
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Although support for PNG format came slowly, new web browsers<https://en.wikipedia.org/wiki/Web_browser> support PNG.
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https://en.wikipedia.org/wiki/GIF#Alternatives

Regarding PNG animation, further down that same page:

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APNG<https://en.wikipedia.org/wiki/Animated_Portable_Network_Graphics> ("Animated Portable Network Graphics") was proposed by Mozilla<https://en.wikipedia.org/wiki/Mozilla> in 2006. APNG is an extension to the PNG format as alternative to the MNG format. APNG is supported by most browsers as of 2019.[63]<https://en.wikipedia.org/wiki/GIF#cite_note-63> APNG provides the ability to animate PNG files, while retaining backwards compatibility in decoders that cannot understand the animation chunk (unlike MNG). Older decoders will simply render the first frame of the animation.
The PNG group officially rejected APNG as an official extension on 20 April 2007.[64]<https://en.wikipedia.org/wiki/GIF#cite_note-64>
There have been several subsequent proposals for a simple animated graphics format based on PNG using several different approaches.[65]<https://en.wikipedia.org/wiki/GIF#cite_note-proposalcomparison-65> Nevertheless, APNG is still under development by Mozilla and is supported in Firefox 3.0<https://en.wikipedia.org/wiki/Mozilla_Firefox#Version_3.0>[66]<https://en.wikipedia.org/wiki/GIF#cite_note-APNG-66>[67]<https://en.wikipedia.org/wiki/GIF#cite_note-mozlabsapng-67> while MNG support was dropped.[68]<https://en.wikipedia.org/wiki/GIF#cite_note-68>[69]<https://en.wikipedia.org/wiki/GIF#cite_note-69> APNG is currently supported by all major web browsers including Chrome (since version 59.0), Opera, Firefox and Edge.

Bottom line:  All X3D PNG3 examples, implementation reports, and open-source code welcome.

Thanks in advance for all efforts, shared lessons learned, and coolness.

Have fun with X3D and PNG 3!  🙂

all the best, Don

--

Don Brutzman  Naval Postgraduate School, Code USW/Br        brutzman at nps.edu

Watkins 270,  MOVES Institute, Monterey CA 93943-5000 USA    +1.831.656.2149

X3D graphics, virtual worlds, navy robotics https://faculty.nps.edu/brutzman

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