[Digikam-users] What am I missing? (16 bit, etc.)

Gilles Caulier caulier.gilles at gmail.com
Fri Jan 9 19:36:07 GMT 2015

2015-01-09 20:16 GMT+01:00 Carl McGrath <cmcgrath5035 at comcast.net>:
> I am fairly certain that JPG (the standard)  is limited to 8 bit x 3
> channels (RGB)= 24 bit depth.

JPEG photo => 8 bits
JPEG medical = 12 bits (pattented and not open source)

digiKam use libjpeg and is limited to 8 bits.

> I believe there is a 16 bit TIFF standard, but that may not be universally
> implemented.

it's standard. libtiff support 16 bits and more. TIFF support more
color depth and floating encoding (HDR).

digiKam support 8 and 16 bits in RGBA color space.

PNG support 8 and 16 in RGBA. digiKAm support it too.

JPEG2000 and PGF as similar encoding features than TIFF with wavelets
compression (that TIFF do not have). 8 and 16 bits are supported by

Other image format are exotic and do not have any particular interest
in photography.

For the future we plan to add WebP format support from Google which
use wavelets compression and 8/16 bits color depth. It's opensource.

I take a look to M$ JPEG-XR (normalized by JPEG group to replace JPEG
in camera). Yes you read right, to replace JPEG. Read wiki page for
details : http://en.wikipedia.org/wiki/JPEG_XR

==> JPEG XR is supported by and "open source" libary from M$ but it's
a patented solution and M$ ask royalties.
So, we can forget for a while this format...

VoilĂ ...

Gilles Caulier

> On 01/08/2015 09:40 PM, Paul Verizzo wrote:
> I've decided to get out of my comfort zone and start experimenting with 16
> bit large sRGB color spaces now that I have a new printer with a pretty wide
> gamut (Canon PRO-100.)
> So I take an MRW image, select to work in ProPhoto RGB (Why not go all the
> way?  Been reading about it, especially on Luminous Landscapte.)  I make a
> few adjustments, such as Levels, then select the 8>16 bit option in Depth.
> When I try to save it as either JPG or TIFF, the file is kept at 8 bits.
> When I try a PNG version, it fails.  I'm sorry, I don't have the program up
> to tell you exactly what the failure message is.
> I've spent a lot of time in the online help and the Help PDF's, and I can't
> find anything that specifically address my simple workflow or why it doesn't
> work.
> Thanks, Paul
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