Re: BGRA, ARGB, etc. suggestion

- Animation?
Animation is good, but for now there is at least two png-based animation 
(apng and MNG) and about no software that work with both.
So I think work on "animation in png" as part of PNG-2.0 will lead to
OR discussion stuck on decision between complexity and features
OR animation will not be supported. may be with all other "2.0" features.

I think animation is important, but it should be wiser to propose 
separate specification.
But it's also important to keep some animation needs in mind, so 
"PNG-2.0"-base animation could be better.

- A larger palette (BIGP),with more than 256 indexes and 32-bit color 
samples?
32-bit greyscale have scientific usage, so I prefer to ask someone who 
use such kind of data.
16-bit palette may be useful, but for pretty low number of scenario.

- Backward compatibility (a PNG-2.0 decoder must handle PNG-1.0 files)?
Definitely yes.

- BGRA and ARGB sample ordering in pixels?
Doubt that it have any usage.


My own thoughts of "PNG-2.0" after FLIF discussion:
1) Add compression methods 1 and 2:
1  LZMA - pretty popular, 'medium level' compress faster and better than 
'heavy level' deflate;
2 ZPAQ(streaming) - one of the most effective, embed description of 
decoding algorithm within compressed data so decoder always decompress 
data of future encoders.

2) Using bit-mask in 'filter' to determine some extension
64 - colour altering. Followed by specific chunk like CLSP (colour 
space) it allow to define other than RGB colours like CMYK, YUV, XYZ, 
LOCO etc.
This could be useful for avoid colourspace conversion e.g. with captured 
frames (most video YUV), also 'prepare for animation'. Altering byte 
order also may be configured this way(still doubt about usage).
May be also configured in 'colour type' byte, I use 'filter' just 
because it was already used this way in MNG.

128 - only with interlaced files. Use previous interlace pass as 
additional 'add' filter. Subtract before main filter on encoding, add 
after main filter after decoding.
This could increase compression rate, but testing required.


22.12.2015 7:55, Glenn Randers-Pehrson пишет:
>
>
>
> OK, let's have at it then.  What does PNG-2.0 need?


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