Re: CFD: zXIF 2017-0207

10.02.2017 20:39, Cosmin Truta пишет:
>
> ICC information is about pixels-to-display or pixels-to-print,
> therefore, if the image gets edited, and don't know what new display
> is being used, you should discard the old info. In conclusion, the PNG
> iCCP chunk is (as it should be) unsafe-to-copy. The same goes about
> sRGB, cHRM and gAMA.
>
> EXIF information is about source-to-pixels, therefore, even if the
> image gets edited, it's still the same source information.
> (Notwithstanding the thumbnails, of course, but that's easy to fix,
> and we already addressed that.) In conclusion, the PNG eXIf chunk
> should be safe-to-copy.
Well, I see I had some misunderstanding about EXIF gamma, but I still 
think it should be unsafe-to-copy(like mentioned in CIPA 2016).

Let's suppose source => processing1 => pixels1 and 'gamma'(or other 
colorspace data) describes processing1
If we do extra processing we result in source => processing1 => 
processing2 => pixels2.
So 'gamma' which describe processing1 will not describe our resulting 
processing (processing1+processing2), and it will be inapplicable for 
pixels2.
> As a further example, take a look at Google WebP container
> specification. Like the current PNG eXIf design that comes in addition
> to our current colorimetry info, they have designed provisions for
> both EXIF and ICC.
> https://developers.google.com/speed/webp/docs/riff_container
Google prefer does not develop their own way to keep metadata and rely 
on EXIF(XMP).
PNG prefer to use own way to keep metadata. That's very important 
difference for me. And that's why I prefer PNG(and don't want it to 
morph into PNG image + EXIF).
> You are right in principle, but it's impossible in practice. EXIF as a
> whole has hundreds and hundreds of fields, describing virtually all of
> the minutiae regarding digital photo capture. The experts who design
> and manufacture digital cameras know exactly what needs to go in
> there, and they do the hard work of agreeing (even if they're
> competitors) and updating the EXIF specification. So what you're
> saying would be nice, but we just don't have such expertise in our
> group, and we should defer to their expertise instead.
It's about 80 if we're talking about EXIF IFD.
TIFF IFD contains generic image attribute most of which or inapplicable 
or could be saved into current PNG structure.
GPS IFD is definitely not best way to save geo-reference. Really, it 
looks like GPX waypoint rewritten with pen and paper and lightly 
augmented (with same pen).

And these 80 attributes is lack some properties which are saved by 
camera makers within 'MakerNote': manual or auto focus(and so we need 
difference between measured subject distance and set focal plane 
distance); type of auto focus; flash energy compensation; age of camera 
(in days or in shots)...

When we try to pass beyond 'camera-to-display' scenario we may also find 
many attributes absent in EXIF:
*several subjects with their description (e.g. for name people on group 
photo);
*precision georeference for aerial/space photo (or artificial 
geo-referenced images like maps), incl. non-Earth coordinates for images 
of Mars etc.
*for digitized classic film there should be two sources(camera and 
scanner) and film description(may be information about film development).
*for science data way to interpret image to science values (temperature 
e.g.)... hey! We have pCAL for this! So we already outperform EXIF, why 
stop?

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