PNG Third Edition support

[JohnRiv]

We currently reference PNG Second Edition.

PNG Third Edition is currently in Candidate Recommendation.

Looking at the WPT tests for PNG and Animated PNG:

• Chrome & Edge have full support
• Safari supports it in the latest version of MacOS
• Firefox does not yet support it, and there are bugs linked from WPT to track them (1862245 & 1862235)

If Firefox lands support for PNG Third Edition within the next few months, we could consider including it.

Also worth noting that at present, caniuse.com and MDN do not have any data around PNG Third Edition support.

@digitaltvguy if you have any additional data points we should reference to be able to confirm PNG Third Edition support in the 4 major browsers, please comment here with that info.

[JohnRiv]

The Firefox bugs are still open, so this likely will not be part of WMAS2024.

[svgeesus]

Also worth noting that at present, caniuse.com and MDN do not have any data around PNG Third Edition support.

For caniuse, see

• Add "CICP in images" Fyrd/caniuse#7031

Also, PNG 3rd Edition has an implementation report which also covers manual tests and the general implementation landscape, not just automatic browser tests:

• https://w3c.github.io/PNG-spec/Implementation_Report_3e/

(We should really move that one old apng test in with the rest of the apng tests

[JohnRiv]

Thanks for the details @svgeesus! That implementation report is excellent. Looks like Firefox & Safari have a few bugs to work through, so we'll reference those reports to track support from them.

[JohnRiv]

We'll close this issue for WMAS2024 and hopefully this can be included in WMAS2025 if the tests pass