Re: Support of RGBA 10x10x10x2 ?

Glenn Randers-Pehrson <[email protected]>
Newsgroups gmane.comp.graphics.png.general
Message-ID <CA+PdXcvhVBQ5Q3yhB3aQ34UMZk3qYD77wV6yOJVNS2K8A4EFAA@mail.gmail.com>
On Sat, Jan 14, 2017 at 10:13 AM, John Bowler <
[email protected]> wrote:

> On Sat, Jan 14, 2017 at 6:48 AM, Glenn Randers-Pehrson
> <[email protected]> wrote:
> > On Fri, Jan 13, 2017 at 2:52 PM, Alexey Solovey <[email protected]>
> wrote:
> >>
> >> Hello. Will support PNG format as RGBA/RGB 10x10x10x2 bits?
> >
> > Yes, of course.  You write a 16-bit RGBA 16x16x16x16 together with
> > the sBIT chunk that conveys the channel depths (sBIT 8 8 8 2).
>
> sBIT 10 10 10 2
>

d'oh, thanks.  That's what I had in mind, but dementia is setting in...


>
> > It takes 64 bits per pixel instead of 32, but I expect that the zlib
> compression
> > makes up for that difference (I haven't tested that).
>
> It's not going to be very good, but it is probably comparable to the
> result of bit-packing the values into 32 bits then LZ77 compressing
> 4-byte pixels.  In neither case are the bit patterns aligned to byte
> boundaries so they don't compress well with LZ77.
>

It also defeats the filtering that is based upon correlation of bytes
between adjacent pixels.

Glenn

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