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Cake day: July 2nd, 2023

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  • 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.



  • 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_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 .

    !<