Re: [Gimp-user] Ppm 16bit handling

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

bruno buys net br (bruno buys net br) 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,

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:

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!




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