Re: EXIF support in PNG [was: Modern compressor]

I think that just embed EXIF data into PNG file as-is is not a very good 
idea.

I made some fast comparison between EXIF and PNG metadata (feel free to 
comment if I made mistakes)
https://docs.google.com/spreadsheets/d/1XYSfWb8KHskGdRMcKbqza2QXafoQw3_pIg66j2LgGOg/edit?usp=sharing

Most generic metadata like resolution, comments, colorspace already 
present in PNG. So what software should do if there is whitepoint in PNG 
cHRM chunk and different white point in EXIF?
But it's possible to want EXIF data for picture-taking conditions and 
keep cHRM to improve compatibility... so at least proposal should 
include list of priorities.
Like "An sRGB <https://www.w3.org/TR/2003/REC-PNG-20031110/#11sRGB> 
chunk or iCCP <https://www.w3.org/TR/2003/REC-PNG-20031110/#11iCCP> 
chunk, when present and recognized, overrides the cHRM chunk." in 
current PNG specification.


And current PNG metadata is better than EXIF when it present: 
international name of author; full-featured ICCProfile... so I prefer to 
use PNG-feature when possible. And wish it could be improved to handle 
for EXIF features (some of them like Lens specification could be easily 
added just as keywords).


01.01.2017 6:08, John Bowler пишет:
> Ok, here is a formal proposal, contained verbatim below and attached:
>
> =================================================
> PNG CHUNK PROPOSAL: eXIf
>
> SPECIFICATION
> =============
>
> The four-byte chunk type field contains the decimal values
>
> 101 88 73 102
>
> The eXIf chunk contains EXIF metadata with a length given by the chunk 
> length.  Such data shall be compatible with specifications issued by 
> CIPA, "Exchangeable image file format for digital still cameras" [CIPA 
> DC-008-2016] or its successors.
> =================================================
>
> -- 
> John Bowler <[email protected] 
> <mailto:[email protected]>>
> +1 (541) 450-9885
> PO BOX 3151
> KERBY OR 97531-3151
> USA
>
>
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