Re: [png-mng-misc] weppy (WebP)

[Glenn Randers-P. <gl...@gm...>]

If it's a new format (e.g., VNG) then the indicator would
be in the 8-byte signature.  Browsers and apps like
ImageMagick (and even file(1)) use that magic.

If it's extending an existing format (e.g. PNG or JNG) then
the indicator would either be a different XHDR #;-(
which could be treated as part of a 16-byte magic number
along with the 8-byte signature
or different parameter values in the existing XHDR (JHDR).

I'd prefer just extending JNG, keeping the existing JPEG
capability and adding VP8 image data and alpha data.

The political problem with mozilla/firefox would probably
continue to exist whether it's called JNG or VNG.  For
them it might have to be called PNG to avoid the appearance
of proliferating formats.

Glenn

On Fri, Oct 1, 2010 at 12:49 PM, John Bowler <jb...@fr...> wrote:
>
> On Fri, Oct 1, 2010 at 6:31 PM, Glenn Randers-Pehrson <gl...@gm...>
> wrote:
>>It would only require some new values of
>>JHDR parameters to specify VP8 compression
>>instead of baseline JPEG and a new chunk
>>(e.g., VDAT) to convey the image data.
> Yes, that generalises usefully to using a MNG based container for any simple
> (non-alpha channel) encoding of image data.  If the decoder doesn't have a
> codec for the RGB information then there's a simple fallback of assuming a
> standard color for the image (probably typically white or black.)
>
> Say XHDR and XDAT, where XHDR contains some reliable indicator of the
> encoding.  The main challenge is to come up with a "reliable indicator'' so
> that appropriate codecs could be found.  The codec would just have to return
> a stream of RGB values (probably 8 bit only.)
>
> John Bowler jb...@ac...
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