I'm probably gonna be massively downvoted for saying the forbidden word but I asked AI to do a summary with references of the forward and backward compatibility of PNG's new version:

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Based on recent search results, the new PNG specification (Third Edition) and its reference library (libpng) maintain strong backward compatibility while introducing modern features. Here's a detailed compatibility analysis:

1. Backward Compatibility (Viewing Old PNGs with New Lib)

• Full Support: The new libpng (1.6.49+) and PNG Third Edition fully support legacy PNG files. Existing PNGs (conforming to the 2003/2004 spec) will render correctly without changes .
• Implementation Stability: Libpng's API evolution (e.g., hiding png_struct/png_info internals since 1.5.0) ensures older apps using png_get_*/png_set_* functions remain compatible. Direct struct access, deprecated since 1.4.x, may break in libpng 2.0.x (C99-only) .
• Security Enhancements: Critical vulnerabilities (e.g., CVE-2019-7317 in png_image_free()) were patched in libpng 1.6.37+, making the new lib safer for decoding old files .

️ 2. Forward Compatibility (Viewing New PNGs with Old Lib)

• Basic Support: Older libpng versions (pre-1.6.37) can decode new PNGs if they avoid new features. Core chunks like IHDR or IDAT remain unchanged .
• New Feature Limitations:
  • HDR Imagery: Requires libpng 1.6.45+ and apps supporting the mDCv chunk. Older libs ignore HDR data, falling back to SDR, which may cause color inaccuracies .
  • APNG Animation: Officially standardized in PNG Third Edition. Older libs (e.g., <1.6) treat APNG as static images, showing only the first frame .
  • EXIF Metadata: New eXIf chunks are ignored by legacy decoders, losing metadata like GPS or copyright info .
• Security Risks: Older libs (e.g., ≤1.6.36) contain unpatched vulnerabilities (e.g., CVE-2015-8126). Parsing malicious new PNGs could exploit these flaws .

Compatibility Summary

Scenario	Compatibility	Key Considerations
Old PNG → New Lib	Excellent	Legacy files work flawlessly; security improved.
New PNG → Old Lib	️ Partial	Basic rendering works, but HDR/APNG/EXIF ignored. Security risks in unpatched versions.
New Features	Conditional	Requires updated apps (e.g., Photoshop, browsers) and OS support .

3. Implementation and Industry Adoption

• Broad Support: Major browsers (Chrome, Safari, Firefox), OSs (iOS, macOS), and tools (Photoshop, DaVinci Resolve) already support the new spec .
• Progressive Enhancement: New features like HDR use optional chunks, ensuring graceful degradation in older software .
• Future-Proofing: Work on PNG Fourth Edition (HDR/SDR interoperability) and Fifth Edition (better compression) is underway .

Conclusion

• Upgrade Recommended: New libpng (1.6.49+) ensures security and full compatibility with legacy files.
• Test Workflows: Verify critical tools handle new features (e.g., APNG animation in browsers).
• Fallbacks for Old Systems: For environments stuck with outdated libs, convert new PNGs to legacy format (e.g., strip HDR/APNG) .

For developers: Use png_get_valid(png_ptr, info_ptr, PNG_INFO_mDCv) to check HDR support and provide fallbacks .

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I see, but the animation feature cant be compatiable no?

downvoters: is it wrong?

And the crawling of flash websites is awful

As you can see it's irrelevant apparently. If it's AI generated it will be downvoted.

I don't know. If the poster couldn't be bothered to fact-check, why would I? It is just safer to assume that it can be misinformation.

Considering it named CVE-2019-7317, which was fixed in April 2019, it's already hallucinating and not worth reading further into it.

2029 Headline: Worlds largest data breach caused by zero day exploit in popular PNG 3.0 renderer

the payload was reportedly embedded in an animated image of the attacker repeatedly flicking his left testicle

I still miss using my iPAQ h4350. It still works; might be time to fire up Doom4CE...

LOL, I heard that gif. Timed it in my mind, on the money OP.

I have a Dell Axim X50v in a box somewhere. I imagine the battery is toast and I'll probably have to keep it in its cradle to remain powered. It was a hell of a machine for it's day.

I went through a succession Windows CE/PocketPC machines back in the day, starting with a Casio Cassiopeia E-115, then an Audiovox Maestro which was a rebadged Toshiba, then an HP iPAQ 2215, and finally the Axim.

The displays on the Maestro and the Axim were really something, and I wish someone would bring these back for a modern smartphone. They were rotten at color accuracy, but both had transflective displays that were fully readable even in direct sunlight. The Axim X50v also had a full 480x640 screen resolution which blew the first few iPhones out of the water on pixel density and even gave the iPhone 4 a run for its money. "Retina" display, my ass.

I had a Microdrive bunged into the CompactFlash slot on my Axim which was... several gigabytes, I don't remember how many. I kept it packed with MP3's, and I had a custom wallpaper with a white-on-chartreuse silhouette of a pacifier on it with the legend, "All 10,000 Songs On Your iPod Suck."

But then the entire PDA market got swallowed in one gulp by smartphones.

Animated PNG has been trying to be an extension to the PNG spec for 20+ years.

APNG - Wikipedia

(en.wikipedia.org)

Speaking for animation, your browser probably already supports APNG. APNG is 21 years old and has decent adoption. But it’s officially part of the club.

That said, APNGs are fat as fuck and they’re a pretty old solution to animated graphics with an alpha channel. Don’t expect to see everyone making APNGs all of the sudden. There is a reason why people have kept it at a distance.

It's not irrelevant, it's that you don't actually know if it's true or not, so it's not a valuable contribution.

If you started your comment by saying "This is something I completely made up and may or may not be correct" and then posted the same thing, you should expect the same result.

The PNG format is made of chunks that have determined roles, and provides provisions for newer "standardized" chunks alongside the custom chunks it had supported until now. It is likely that PNG made with newer software that does not use new features, or uses only additional features, will remain readable by older software to some extent.

Likely, you'll see the first frame only on older software. Encoding animation in a dedicated animation chunk and using the base spec for the first keyframe sounds like the sane thing to do, so they likely did that.

I'm not going to look into it now, because I would then have to implement it.

Yes. But if you live in the future, you have to wait for dozens of dozens of intermediate to do so! Great!

Flash was a security nightmare all round, not counting the security flaws. It was just designed without any security features. It was also terribly inefficient at its core job, that was supposedly vector animation. It filled a gap in a time where browser and standards where not that advanced.

Over time, Flash issues where never resolved, but the bloatness of the software kept increasing. Along the way, HTML got better specs, JavaScript got vast improvement, especially in everyone adhering to roughly the same standard (thanks microsoft for finally caving in…), and so the flash interpreter was highly redundant with the browser itself.

For a while flash editors could export in HTML5 and you'd get roughly the same result, but with a fraction of the resources requirements, so naturally there was little incentive to keep the flash player around.

I'm not sure if "killing flash" could be attributed to their author, or to the loss of interest.

Also note that alternative flash players exists to still play older swf files, and some sites uses them alongside with plain video conversion for flash animations that weren't dynamic.

I'll tell you if I can find some new files for testing.

Even JPEG isn't always back compatible either. I loaded an image into my software which uses some ancient library internally, and it swapped the blue and red channels.

Now if anyone don't mind explaining, PNG vs JXL?