Re: Getting APNG support into libpng

On 2021-05-05 23:42, Bob Friesenhahn wrote:
> The level of support in browsers is interesting.  I did not know that.

In addition to browsers, there is native app support.

For example, the animated "stickers" in Apple iMessage are actually APNG

https://developer.apple.com/design/human-interface-guidelines/ios/extensions/messaging/

>
> I have not read the patch.  What is the nature of the patch?  Is it 
> offered under a license compatible with the libpng license?

My understanding is that there are multiple unofficial patches.

People are producing them because they are needed, not because they want 
to. I wasn't suggesting taking a particular patch and merging it 
(although that might work, if it is technically good and, as you say, 
the license is suitable).

Instead I was suggesting that official support in libpng was blocked on 
having an official specification to refer to; and once that hurdle is 
gone then there should no longer be a need for these patches because 
support could be added in libpng itself.

>
> Why would incorporating APNG support (whatever that may mean) in 
> libpng cause a problem?
I don't see that it would be a problem.
>
> Libpng itself is not a specification, but it does have ABI and API 
> commitments for existing usages.
Agreed, and for backwards compatibility those should not be broken.
>
> Usually there is a lot of work done in apps supporting PNG to make 
> reading and writing PNG a reality.  I expect the same would be 
> required for APNG.
Yes. libpng is a library, not a fully-fledged solution.

-- 
Chris Lilley
@svgeesus
Technical Director @ W3C
W3C Strategy Team, Core Web Design
W3C Architecture & Technology Team, Core Web & Media



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