16bits per channel images with GIMP ?

[Bernard DEBREIL]

Hi there !

With The GIMP 1.2, is it possible to open and interpretate tiff images
having 16 bits per channel ? I ran a test with images that were built up
from raw data collected from my Canon PowerShot G2 digital camera. I built
the same image into a 8bits/channel tiff for one, and into a
16bits/channel for the second one. I opened both with GIMP. Both did
opened... but the 'View Info Window' utility read the same thing for both,
that is, 'visual depth 16' (whatever it means... since it may not be 16
bits per channel !), visual depth 16, for both images, the 8bits/channel
one as well as the 16bits/channel.

--

Bernard DEBREIL

[Branko Collin]

Bernard DEBREIL <bdeb...@teaser.fr>, you wrote on Fri, 16 Aug 2002
02:17:03 +0200:

See <http://groups.google.com/groups?q=gimp+%2216+bits%22>.

--
branko collin
"i brought you a tuna sandwich. they say it is brain
food. i guess that is because there are dolphins in
it. they are smart animals" - marge simpson

[Leonard Evens]

Bernard DEBREIL wrote:
> Hi there !
>
> With The GIMP 1.2, is it possible to open and interpretate tiff images
> having 16 bits per channel ?

You can open such images, but they are converted to 8 bits per channel
immediately. I do it all the time.

> I ran a test with images that were built up
> from raw data collected from my Canon PowerShot G2 digital camera. I built
> the same image into a 8bits/channel tiff for one, and into a
> 16bits/channel for the second one. I opened both with GIMP. Both did
> opened... but the 'View Info Window' utility read the same thing for both,
> that is, 'visual depth 16' (whatever it means... since it may not be 16
> bits per channel !), visual depth 16, for both images, the 8bits/channel
> one as well as the 16bits/channel.

I just scanned a b/w negative with Vuescan at 16 bits per channel and
wrote it out as a tiff file with 16 bits per channel. I opened it in
the Gimp (1.2.1) and it said it was a grayscale image with visual depth
24. It certainly doesn't have 24 bits per channel, since when I save
the file without compression, I get just about the right number of bytes
for a b/w image with 8 bit color depth. So I assume this is just a
minor glitch in the Gimp info tool.

Try saving the file with the Gimp and seeing how large it is.

>

--
Leonard Evens l...@math.northwestern.edu 847-491-5537
Dept. of Mathematics, Northwestern Univ., Evanston, IL 60208