Raw processors and digikam

[Juan José Casafranca]

Hi everybody, 

I'd like to implement a feature (https://bugs.kde.org/show_bug.cgi?id=374655) 
to combine the processing strength of raw processors and the management 
capabilities of digikam.

Right now, when a raw file is found in the library, the thumbnail only shows 
the embedded jpg and when you open it in the viewer, the same happens. My 
proposal is to enable a way to perform the edition defined in the raw processor 
(in any raw processor) and show the processed image in the thumbnail and in 
the viewer. 

I can do this, but I need some help to know where to begin. The tasks I have 
found are the following:
1. Define a raw processor to be used. The user must select a raw processor to 
process the raw files. This processor can be the internal one or an external 
one such as darktable. 
2. Detect when an edition has been done in the raw file. This is tricky as the 
raw file is not edited, but a sidecar file (in darktable for example, the 
edition is stored in a xmp).
3. When an edition has been done, update thumbnails and preview if necessary. 
The thumbnail will be generated calling the raw processor with the 
corresponding edition (I already have this part)
(4.) It's normal to have several editions for one raw file. If possible, show 
all the different editions in the library. (x.NEF may have x.NEF.xmp, 
x_1.NEF.xmp and x_2.NEF.xmp, the three of them should be shown)

I'm having lot of trouble understanding how to update the thumbnail when the 
image is developed (point 2) so some guidelines will be helpful.

Any idea to do this will be also helpful!

Thanks! :-)