[Digikam-users] Color depth in lossless formats

Niels Ott niels at delta-b.net
Wed Aug 27 10:23:12 BST 2014

Am 26.08.2014 um 22:06 schrieb Milan Knížek:
> Things might have change since I looked at JPEG2000 implementation:
> then, it was not capable of storing colour profile (ICC). 

At least with my version of DigiKam, there is no color profile stored.
So on re-opening with the image editor, DigiKam asks which profile to use.

> Also check if
> it can store XMP (well, you could workaround that by a side-car file,
> even that it is not so convenient).

Wikipedia says, JPEG2000 has space for arbitrary meta data stored as
XML. Furthermore, XMP seems to be based on RDF, which again often uses
XML for actual data storage. Hence it should be possible, but it's most
likely not implemented.

> It is a pitty they kept the wavelet compression proprietary, they just
> digged a grave for it.

Apparently yes.

I'm still not decided. For me it is not important that JPEG2000 isn't
supported by many programs. Except for Gimp, whose additional JPEG2000
plugin I still need to try. I use Gimp when I edit images for putting
them on the web (as normal JPEG).

So to me, there are two major points about a lossless format:

a) Can it be opened by the (few) tools I need in a
   convenient way (slow? hard to use?)

b) Can I convert it to something else in a couple of years/
   will the format still be supported?

It's hard to judge about b) for me. Thinking back, PNG was so great when
it was new, but it took years for browsers to support it, even though it
was explicitly made for the web. But PNG is open, JPEG2000 isn't exactly.

> Only when it is intended for print on sufficiently capable printer, I
> use 16-bit TIFF.

For many images, I don't know where they'll end up. I put some on the
web, but I also give some to labs to get real prints. So I rather don't
want to lose anything in between. My favorite photo lab btw accepts
16bit PNG files on CD, so I actually never go lossy.


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