Documentation of XMP-files darktable creates

AxelG · May 5, 2019, 1:08pm

Hello all,

after some conversation with Gunther Wegner, the developer of LRTimelapse he does have a look into the xmp-file-structure, wich darktable creates. And hopefully (at least in my dreams ) some day, LRTimlapse might support darktable.

As he already asked on the mailinglist, I’d like to raise this topic here as well:

Is there any documentation of the base64 coded and gziped strings
as dt is able to import Lightroom’s xmp-files, do we have a chance to export as well to Lightroom-“standards” (sorry if that is a silly question, in case already available)

paperdigits · May 5, 2019, 4:47pm

Darktable’s lightroom import is very limited. LR might be able to read dt’s tone curve, but you’d need to put it in the right place for LR.

AxelG · May 5, 2019, 7:37pm

o.k., let’s stick to the first item. First things first is there a doc for darkable’s xmp?

gwegner · May 6, 2019, 6:15am

Im adding my original request in the mailing list here for clarification:

Is there any documentation about the way, DT stores its values in the XMP
files?

From what I know, XMP was intended to be an open, readable format which
should allow to interface between different programs. Even if this mostly
doesn’t work, because most applications use their own way of implementing
it, at least many use a readable format. I’m a bit surprised that darktable
chose an all encrypted and compressed format to store its parameters which
makes it hard to interface.

So my question is, if there is a documentation on how to decode / encode
the chosen format?

I’m asking, because I’m the developer of LRTimelapse, which currently interfaces
with Lightroom via XMP files. I’m evaluating the options to use alternative
Raw Converters also.

AxelG · May 6, 2019, 10:22am

@Pascal_Obry
Could you gide me to the proper files in the code, please. In case no doc avaliable (which I can hardly imagine as 2.7 got an update to V 3.0) I will study the code and prepare a doc.

If it is not beyond my competences

Pascal_Obry · May 6, 2019, 5:02pm

You mean the code that handles lr → dt import?

If that’s it, it is there:

github.com

darktable-org/darktable/blob/master/src/develop/lightroom.c

/*
    This file is part of darktable,
    Copyright (C) 2013-2021 darktable developers.

    darktable is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    darktable is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with darktable.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "develop/lightroom.h"
#include "common/colorlabels.h"

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AxelG · May 6, 2019, 10:22pm

Dear Pascal,

actually we meant the dt-xmp definition.
However, Johannes already replied the situation on the mailinglist

Let me digest this first and rephrase the wishes/proposals