Re: BGRA, ARGB, etc. suggestion

not being a graphics scientist or expert in any sense, but I can see the 
importance of 32 bit grayscale PNG files for certain applications

yeah, of course it doesn't make any difference for visual appearances

but if you have those bitmaps from some type of scientific data 
collection, you will have to store them somehow? so why not in a PNG file

each time I hear this "oh, but that will break the PNG specification 
standard" I'm cringing, because if that is really true we didn't do a 
good enough job of creating a standard that would be extendable and flexible

I'm not saying that 32 bit grayscale graphics is important enough for 
the effort to do an upgrade of PNG, but hey we're here now 20 years 
after the fact, upgrades should be possible, we don't want to become 
"cast in stone"  <g>

and I personally think this is a really good one to prove or test how 
flexible the PNG standard really is ...

20 years with no change is too long !!

Willem




On 2015-12-20 16:17, Glenn Randers-Pehrson wrote:
> chNL would compete with Apple's CgBI chunk and perhaps violate their
> "patent applied for".  Even though the proposed name is different, it
> would serve the same purpose: making PNG files unreadable.
>
> Libpng supports BGRA and ARGB (reads RGBA pixels from a PNG file and
> converts them on-the-fly to your desired format.
>
> Supporting 32-bit samples would not be trivial because the spec and
> library would have to be redone to allow values greater than (2^31 - 1)
> so I don't expect that proposal would be accepted.
>
> The PNG specification itself says that chunks like chNL and CgBI violate
> the guidelines for new PNG chunk types:
>
> http://www.w3.org/TR/PNG/#B-NewChunksAppendix
>
> "Do not define new chunks that redefine the meaning of existing chunks
> or change the interpretation of an existing standardized chunk, e.g., do
> not add a new chunk to say that RGB and alpha values actually mean CMYK."
>
> Glenn
>
> On Sun, Dec 20, 2015 at 3:16 PM, Alexey Solovey <[email protected]
> <mailto:[email protected]>> wrote:
>
>     Hello. I suggest to make chNL chunk for declare how should works
>     png: in BGRA, ARGB, or another format. Also I suggest 32-bit
>     grayscale support.
>     Probably, I suggest maSK, that released in BMP format. Glenn?
>
>
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-- 

Willem van Schaik
<[email protected]>
http://www.schaik.com/


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