Hi all,
I noticed that when I open a 16bit ppm in GIMP 2.8, the file opens without the 'gimp can't handle 16bit, it will loose data, etc...' notification. But if I open a tiff version of the very same raw file, the notification does pop up. My understanding is that current GIMP 2.8 can't handle 16bit, regardless of file format. Is that right?

Bruno Buys

On 05/07/12 06:04, Simon Budig wrote:

bruno@buys.net.br (bruno@buys.net.br) wrote:

I noticed that when I open a 16bit ppm in GIMP 2.8, the file opens without the 'gimp can't handle 16bit, it will loose data, etc...' notification. But if I open a tiff version of the very same raw file, the notification does pop up. My understanding is that current GIMP 2.8 can't handle 16bit, regardless of file format. Is that right?

Yes, these warning dialogs are generated by the file-format plugin and it seems the ppm plugin just silently discards data.

Gimp 2.8 is limited to 8 bit per channel, but if you feel adventurous you are invited to try the current git version of babl/gegl/gimp and experiment with the new high-bit-depth support. This still is strictly unstable and has an inconsistent UI in lots of places. It is fun though :)

I hope this helps,
Simon

Hi,
So after a bunch of package installing and compiling, I am successfully running Gimp 2.9.1 from git, on debian wheezy. The thing is, when I open a 16bit tiff, Gimp *still* pops up the "can't handle 16bit,
information will be lost...". After opening the file I go to Image > Precision and change
to 16bit. But from what I understand, setting the file to 16bit *after* it was downed
from 16 to 8 doesn't help. Information was already discarded in the first conversion.
I don't understand: can't Gimp just open the file as it is, with no conversion whatsoever, since
support to 16bit is there?

Thanks much,

Bruno

On Thu, 24 May 2012 10:27:30 +0200, Simon Budig wrote:

bruno@buys.net.br [1] (bruno@buys.net.br [2]) wrote:

The thing is,

when I open a 16bit tiff, Gimp *still* pops up the "can't handle 16bit, information will be lost...". After opening the file I go to Image > Precision and change to 16bit. But from what I understand, setting the file to 16bit *after* it was downed from 16 to 8 doesn't help. Information was already discarded in the first conversion.

I am

working at the TIFF plugin and some tiffs get loaded correctly

(while

others are broken at the moment). Tiff is quite convoluted and

has a

ton of different options. It is hard to wrap your mind around it.

I don't understand: can't Gimp just open the file as it is, with no conversion whatsoever, since support to 16bit is there?

Well,

unfortunately it is not that easy. There is a certain API

available

for the file-plugins that transfers the image data to the Gimp

core.

That API was only prepared to accept 8 bit images. The transition

of

the core to a wider range of data formats did not change the old API,

since we wanted to keep compatibility for the plugin (or all plugins

would have disappeared simultaneously).

Hence we had to invent a

second set of API functions that support the

new data formats.

However, this means that the plugins which want to

make use of the new

data formats need to be changed to use the new API.

In a lot of cases

this is quite easy and means less code in the plugins,

but the changes

have to be done and it is real work.

Porting the p*m-Plugin

(plug-ins/common/file-pnm.c) should be easy. The

file-format is as

simple and straight-forward as it gets. If you want to

dabble with

development and help with the progress of Gimp you are

welcome to take

a shot at it. If you catch me in IRC (#gimp, nomis) I'll

be glad to

give assistance.

Have fun,
Simon

Hi Simon!
That´s very friendly
of yours to reply in such detail. Now I feel like my first email was a
little "clientish". Sorry for that. Gimp isn´t a private company.

I am not of much help as a coder, but I can provide files and give feedback
in testing.

Good news is, since you said you are working in 16bit tiff, when its done,
it will be huge. Tiff is an important bridge for those of us converting from raw.

Other good news is, I was able to load, work and save a 16bit png file, following this
post:
http://libregraphicsworld.org/blog/entry/gimp-2.8-released-next-version-to-get-high-bit-depth-precision

The file was converted from tiff to png with 'convert', and opens without the
loose data notification. After opening, the precision is indeed set to 16bit.

All the best!

Bruno

Links: ------
[1]
mailto:bruno@buys.net.br
[2] mailto:bruno@buys.net.br