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A new PNG spec

(www.programmax.net)
612 points bluedel | 3 comments | 24 Jun 25 13:01 UTC | HN request time: 1.399s | source
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ProgramMax ◴[25 Jun 25 19:00 UTC] No.44380761[source]▶
Author here. Hello everyone! Feel free to ask me anything. I'll go ahead and dispel some doubts I already see here:

- It isn't really a "new format". It's an update to the existing format. - It is very backwards compatible. -- Old programs will load new PNGs to the best of their capability. A user will still know "that is a picture of a red apple".

There also seems to be some confusion about how PNGs work internally. Short and sweet: - There are chunks of data. -- Chunks have a name, which says what data it contains. A program can skip a chunk it doesn't recognize. - There is only one image stream.

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fwip ◴[25 Jun 25 20:05 UTC] No.44381338[source]▶
Do you have any examples on hand of PNGs that use the new features of the spec? It would be cool to see a little demo page with animated or HDR images, especially to download to test if our programs support them yet.
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ProgramMax ◴[25 Jun 25 20:21 UTC] No.44381484[source]▶
Sure!

Chris Lilley--one of the original PNG co-authors--has a post with an example HDR image: https://svgees.us/blog/cICP.html It is about half way down, with the birthday cake. Generally, us tech nerds have phones that are capable of displaying it well. So perhaps view the page on your phone.

What you should look for is the cake, the pink tips in her hair, and the background being more vivid. For me, the pink in the cake was the big give-away.

There is also the Web Platform Tests (WPT) which we use to validate browser support: https://wpt.fyi/results/png/cicp-chunk.html?label=master&lab...

Although, that image is just a boring teal. See it live in your browser here: https://wpt.live/png/cicp-chunk.html

For an example of APNG, you can use Wikipedia's images: https://en.wikipedia.org/wiki/APNG

But you have a bigger point: I should have live demonstrations of those things to help people understand.

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1. Nopoint2 ◴[26 Jun 25 05:12 UTC] No.44384351[source]▶
I never realized how limited sRGB is. I guess this is why people liked CRT TVs, and why you could never watch analog TV properly on a PC screen.
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2. account42 ◴[26 Jun 25 08:35 UTC] No.44385411[source]▶
It's really not that limited, the problem is only if you reinterpret a larger gamut as sRGB without doing the proper conversion where things look washed out.
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3. Nopoint2 ◴[26 Jun 25 13:55 UTC] No.44387463[source]▶
That's what I thought too, but the difference is big. You'd think you maybe lose some color lights, or very bright flowers, but no, colors outside sRGB are common.

There was nothing you could do about the TV, the screen couldn't show all the colors that you needed.