Re: CFD: eXIf 2017-05-31

On 1 June 2017 at 10:09, Glenn Randers-Pehrson wrote:
> On Thu, Jun 1, 2017 at 9:55 AM, Pavel Zlatovratskii wrote:
>
>> Within safe-to-copy eXIf it became real as eXIf (with preview) could be
>> copied on crop by software which don't know anything about it.
>
> It's already real regardless of PNG eXIf.  ImageMagick preserves the
> original thumbnail in a JPEG->crop->JPEG operation (along with
> all of the other copy-unsafe material).  I agree that that's a shortcoming
> of ImageMagick, and am working to improve that, but it's a fact
> of life all the same.

For example, XnView has a menu option in which the user may disable or
enable the automatic update of the thumbnail. In older versions,
XnView did not even update the thumbnail at all.

It is a fact of existing EXIF-processing software that thumbnails (as
much as any other EXIF fields) are not required to be updated.

On 1 June 2017 at 09:31, Pavel Zlatovratskii wrote:
>
> And all these 'maybe' is looks like extra complexity for me, definitely not
> KISS.

There is no gratuitous complexity involved here. The current
specification merely acknowledges the *fact* that EXIF fields may be
not up to date. You, as a developer, have no control in general, given
that you have to handle images coming from unknown sources. Exceptions
are specific software development scenarios where you happen to have
"independent knowledge" -- which is when you happen to *know* that the
EXIF data is coming from a source within your trust and control. But
these are only exceptions.

Sincerely,
Cosmin

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