Re: DRAFT: eXIf 2017-03-02

Well, I agree about compatibility, but compatibility does not mean 
"repeat JPEG header as-is is only solution".

E.g. using separate preview chunk with PNG or JPEG image will very 
slightly differ from IFD[1], even with some advantages:
*While converting to PNG JPEG|TIFF header anyway should be parsed to 
keep resolution, copyright etc. in PNG chunks. So it's not too hard 
extract data in JPEG preview or repack to PNG preview (we already have 
to repack main image).
*Reverse convert is also simple for same reasons.
*View of preview is even easier if preview is PNG as PNG viewer should 
have PNG decoder, but may not have JPEG decoder.
*Updating of preview is easier as there is no need to rehash main 
metadata EXIF. And there is no need to rehash preview when updating EXIF 
metadata.

So what benefit in usage IFD[1] instead of separate chunk? I see no 
increase of compatibility (software anyway will require new chunk 
handlers), but see possible decrease of it (using preview of PNG more 
often require JPEG decoder; less confident about if thumbnail match main 
image).


06.03.2017 21:49, Chris Lilley пишет:
> It is a late entrant in an EXIF-enabled field already occupied by JPEG
> and TIFF. To that end, anything which makes it harder to move EXIF from
> a JPEG to a PNG, and in particular  harder to move it from PNG to JPEG
> (as would happen at the end of an editing workflow), decreases the
> viability of the solution.
>
> Maybe compatibility with existing workflows should be listed as an
> explicit goal?
>

-- 
Have a nice DOS.

Pavel Zlatovratskii [email protected]; [email protected]


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