Mailinglist Archive: opensuse (1045 mails)

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Re: [opensuse] Writing coments on photos problem - yes, again! O:-)


31. ledna 2016 15:04:48 CET, Anton Aylward <opensuse@xxxxxxxxxxxxxxxx> napsal:
On 01/31/2016 04:53 AM, Vojtěch Zeisek wrote:
I do not trust any
tool saving comments outside commented files and specifically I do
not trust KDE
semantic tools in this way because of various problems and
technological
instability. My personal impression, but no, thanks. Good for
searching, not
for storing extra information.

Indeed!
And ultimately its not about trust.
it's an operational thing.

Storing any such information outside the file means it can be 'left
behind'. it means it is platform dependent, the platform being not
simply Linux vs OSX vs Windows, but which DM to use, which applicaiton
to use.

That's the whole point of embedded metatdata.

Some file systems even have 'forks' in the file, the file, rather than
being an array of bytes, has branches, is itself a database.
if effect this is what the exif data is.
The 'header' has a number of fields, some of which are pointers.
They may point to the actual data. In the case of many video files
there may also be a pointer to an embedded snapshot.

Now here is the kicker:
There are purists out there who say you should !NEVER! edit the exif of
the sources images. they say this about the RAW images from cameras
and
even from scanners and many tiffs, jpgs and gifs that are produced by
proprietary systems. They claim that only the vendor really knows what
the fields and pointers are, regardless of the standards in this area,
regardless of our skills at reverse engineering.

Ultimately, those header tables are not much different from the header
tables of many program load images and their link tables. We've over
half a century of dealing with linkage editing. We've almost as much
experience in reverse engineering even when the vendors/manufacturers
don't publish data, and many of the video/camera manufacturers DO
publish their specs.

And we have plenty of examples of the reverse engineering 'hackers'
ending up knowing more than the manufacturers and finding bugs and
inconsistencies!

Its one thing to apply j.random.edit to the exif, as it is to any file,
but there are some exif/IPC field s that are clearly there
input/update:
comment, author, description, copyright. In the limiting case, saying
that a copyright stamp should be in an external database that has no
inherent association with the image is, in my opinion, lunacy! Ask
someone who has had their image or recording pirated and relied on the
EMBEDDED copyright information to make their case.

I've had this argument with the authors of 'darktable'. They feel its
adequate to leave the original files alone and have the extra stuff in
a
XML sidebar file, and then their software add it when the generate a
jpg
or gif. They don't see that they, in turn, are applying an edit and
generating their own table and set of pointers in this image. And of
course its "documented" because their code is open source.

The idea that authorship and copyright should be applied as early as
possible and in a way that is tightly associated with the ORIGINAL
image
(rather than derivative works) seems to escape them, but then this gets
down to being a legal issue rather than a technological one.
Having the copyright claim in a sidebar file or in an external database
raises many legal issues.

Its not as if we are talking about editing any of the technical fields,
the EV, aperture, shutter. In fact editing those fields would not
involve restructuring and altering length of fields and hence pointers.

Yes, yes, yes! And how is it with that interoperability then? Metadata inside
files are the most portable and easily managed.

--
Vojtěch Zeisek
http://trapa.cz/cs
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