On Wed, 20 Aug 2003, Leonard Rosenthol wrote:

> At 11:42 PM +0000 8/13/03, Phil Harper wrote:
> >well, it'd be interesting to see if Adobe added XCF to Photo$hop,
> >after all, GIMP is the competition, it wouldn't be in their
> >interests to support a multilayered image format that it controlled
> >by someone else(although they might support PSP, i don't know
> >haven't checked.)
>       They support a number of formats that they don't control -
> because they are standard formats that their customers are
> requesting.   But today XCF isn't one of them, and probably won't be
> for a while.

AFAICT, there is nothing stopping Gimp developers from creating a
potatoshop plugin that can read XCF.

> >it'd be nice if your app could read and render a flat version of the
> >image if you don't support layers i supose, this is an interesting
> >one since all these different target apps will handle things like
> >layermodes differently, and some wouldn't even be supported.
>       EXACTLY my point!
>       Whatever file format we end up with, we need to accept that
> not all consumers of that file format will be able to support 100% of
> the features (perhaps not even GIMP itself).
> >no, that simply wouldn't be flexible enough, surely, i mean you
> >could have extra data about how do use the layers in the TIFF but if
> >those aren't recognised by other readers you just get a strange
> >result and a confused decoder.
> >
>       You could get that just as easily with XCF when a given
> consumer/reader doesn't support 100% of the features of the format...

With a PNG style format, this becomes much less of an issue.  First, PNG
requires all readers to be able to interpret a core subset -- anything
that can't interpret it violates the standard.  Second, all chunks are
tagged "optional" (meaning that they can be safely ignored if not
understood" or "mandatory" (in which case the reader will give up if it
doesn't understand the chunk.)  This means that a baseline PNG can be read
by any compliant program (hello, IE!) without problem, and any extensions
will either degrade gracefully or cause an error, but in no case will  the
decoder become confused and return a strange and wrong result.

In this way, for example, someone could create a PNG chunk that indicated
that the data was in Lab space, and a decoder that didn't recognize that
feature would just give up instead of returning some garbage where the red
channel gets luminence, etc.


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