Re: Why there is no 360 degree support in PNG?

On Mon, Nov 28, 2016 at 7:06 PM, Alexey Solovey <[email protected]> wrote:
> May need develop PNGs (sPNG, PNG-360, VR-PNG) ?

I think this is a question for the PNG list isn't it?  I posted this
response there and blind-copied to the libpng implementation list.
The original list is about one specific implementation of the PNG
standard; standard questions go to the PNG discussion list.

A 360 degree image is trivial to represent; you just need to define a
chunk to say the image is 360 degrees and get it adopted widely.
Anyone can do the first thing, doing the second simply requires
adoption among the '360' community.

Did you mean a spherical image?  The answer is the same but the chunk
has to say what the mapping is to a rectangle, but that's just
something like the Mercator projection isn't it?  (I really don't know
anything about this stuff; Mercator took a sphere and projected it to
a cylinder, right, then that is 360 degree image, I think.)

Someone who knows has to define the chunk, get wide acceptance in the
community and I think that would be it so long as it meets the base
requirements of PNG (single image, the chunk or chunks can be ignored
and and the image seems vaguely reasonable.)

The only obvious restriction that I can see is that the data must be
represented as a rectangular array of co-sited color and alpha
information.  (No light fields, no 3D beyond what sTER can already
do).

John Bowler

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