Re: CFD eXIf 2017-05-31 [was DRAFT: eXIF 2017-05-28]

On Thu, Jun 1, 2017 at 8:07 AM, Pavel Zlatovratskii <[email protected]> wrote:
>
>
> 01.06.2017 11:11, Glenn Randers-Pehrson пишет:
>>
>> eXIf chunk is designed to be simple toencode. As willem said, KISS (keep
>> it simple, stupid).
>
> Ok. I agree with eXIf chunk written as direct copy of EXIF data. However I
> disagree that anyone could rely on such 'raw' data.
> I think encoder should be able to parse EXIF if it want to keep
> unsafe-to-copy metadata, but it may not parse by cost of loosing
> unsafe-to-copy data(as any decoder should discard this data).
>
> I don't think it is possible to keep unsafe-to-copy data within safe-to-copy
> chunk and rely on them.

I think this paragraph in the current eXIf CFD provides sufficient
warning against relying on the 'raw' data:

The eXIf chunk contains metadata concerning the original image data.
If the image has been edited subsequent to creation of the Exif
profile,
this data might no longer apply to the PNG image data. It is beyond
the scope of this specification to resolve potential conflicts between
data in the eXIf chunk and in other PNG chunks. It is recommended that
unless a decoder has independent knowledge of the validity of the Exif
data, the data should be considered to be of historical value only.

Glenn

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