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.
Comment on PNG has been updated for the first time in 22 years — new spec supports HDR and animation
db2@lemmy.world 8 months ago
But is it backwards compatible with an old version that can’t be updated?
cley_faye@lemmy.world 8 months ago
Ghostalmedia@lemmy.world 8 months ago
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.
Tetsuo@jlai.lu 8 months ago
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:
!
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_infointernals since 1.5.0) ensures older apps usingpng_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
IHDRorIDATremain unchanged . - New Feature Limitations:
- HDR Imagery: Requires libpng 1.6.45+ and apps supporting the
mDCvchunk. 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
eXIfchunks are ignored by legacy decoders, losing metadata like GPS or copyright info .
- HDR Imagery: Requires libpng 1.6.45+ and apps supporting the
- 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 .!<
sem@lemmy.blahaj.zone 8 months ago
I do not have downvotes on my instance, so please, have a 👎
Artisian@lemmy.world 8 months ago
downvoters: is it wrong?
kungen@feddit.nu 8 months ago
Considering it named CVE-2019-7317, which was fixed in April 2019, it’s already hallucinating and not worth reading further into it.
hardware26@discuss.tchncs.de 8 months ago
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 is misinformation.
Tetsuo@jlai.lu 8 months ago
If you prefer to know nothing about PNG compatibility rather than something that might be true about PNG. That’s fine but definitely not my approach.
Also, as I said to another commenter. Critical thinking is not some tool you decide to use on some comments and not others. An AI answer on some topics is actually more likely to be correct than an answer by a human being. And it’s not some stuff I was told by an AI guru it’s what researchers are evaluating in many universities. Ask an human to complete various tasks and then ask the AI model and compare scientifically the data. And it turns out there is task where the AI outperforms the human pretty much all the time.
YET on this particular task the assumption is that it’s bullshit and it’s just downvoted. Now I would have posted the same data myself and for some reason I would not see a single downvote. The same data represented differently completely change the likelihood of it being accurate. Even though at the end of the day you shouldn’t trust blindly neither a comment from an human or an AI output.
Honestly, I’m saddened to see people already rejecting completely the technology instead of trying to understand what it’s good at and what it’s bad at and most importantly experiencing it themselves.
I wanted to know what was generative AI worth so I read about it and tried it locally with open source software. Now I know how to spot images that are AI generated, I know what’s difficult for this tech and what is not. I think that’s a much healthier attitude than blindly rejecting any and all AI outputs.
Tetsuo@jlai.lu 8 months ago
As you can see it’s irrelevant apparently. If it’s AI generated it will be downvoted.
null@slrpnk.net 8 months ago
It’s not irrelevant, it’s that you don’t actually know.
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.
muntedcrocodile@hilariouschaos.com 8 months ago
Yes that’s why its so great
Deebster@infosec.pub 8 months ago
Some of this is paving the cowpath - the animated PNG stuff is 20 years old and e.g. Firefox has had support since March 2007.
otacon239@lemmy.world 8 months ago
Yeah, this was my first thought. How many slightly older, no-longer-being-updated pieces of software will fail to open the new version? Hopefully it’s built in a way that it just falls back to legacy and ignores the extra information so you can at least load the file.
dual_sport_dork@lemmy.world 8 months ago
I mean, that’s already how animated .gifs work. If somehow you manage to load one into a viewer that doesn’t support the animation functionality it will at least dutifully display the first frame.
How the hell you would manage to do that in this day and age escapes me, but there were a fair few years in the early '90s where you might run into that sort of thing.
BurgerBaron@piefed.social 8 months ago
One example is piefed unfortunately. Animated gifs as avatar or banner don't animate currently as far as I can tell.
dual_sport_dork@lemmy.world 8 months ago
Those are displayed in browser, right? The only reason that would be happening is if Piefeed is recompressing images and their code is not smart enough to identify an animated .gif and act accordingly.
awesomesauce309@midwest.social 8 months ago
Probably most notably the iOS photos app until like 2014
pennomi@lemmy.world 8 months ago
Popular photo and video editing apps like Photoshop, DaVinci Resolve, and Avid Media Composer already support it, alongside Chrome, Safari, and Firefox. Apple’s iOS and macOS also work with the new file standard.
This is all the article mentions. I hope you’re right about the backwards compatibility.
ouRKaoS@lemmy.today 8 months ago
I remember the Wild West Web days when it was a toss up seeing if animated Gifs, transparencies in images, or the specific hexadecimal for your personal shade of purple you created would render properly between browsers.
Blackmist@feddit.uk 8 months ago
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.