[digiKam-users] How to rebuild RAW thumbnails?

[Maik Qualmann]

We can also automate the behavior by changing 2 lines of code. If the 
extracted preview image of a RAW file is a grayscale image, we will read the 
RAW image. Now would then RAW files always colored. Would this behavior be 
okay?

Maik

Am Mittwoch, 3. Oktober 2018, 12:09:43 CEST schrieb Cirrus:
> As others have said, the value of seeing the b&w jpeg immediately after
> taking a shot is nearly critical.  Plus the particular rendering this
> camera produces is something I very much like.
> 
> The point about the impact on speed in DK if the embedded raw thumbnail is
> regenerated is a serious concern.  Although doing so should be optional and
> a user would likely understand they are invoking a penalty.
> 
> That said, darktable does this (as an option for a thumbnail outside of the
> raw) and the penalty, to me, is quite minor. I'd very much like to have the
> choice in DK.
> 
> Given all the information everyone has kindly provided here (Thank you!),
> it doesn't seem like there's a easy solution.  I'll probably continue doing
> organization and tagging in DK but move culling and rating over to
> darktable.  So it goes.
> 
> On Sat, Sep 29, 2018, 04:59 Gilles Caulier <caulier.gilles at gmail.com> wrote:
> > Hi,
> > 
> > Changing the color space in camera while shooting will affect preview
> > included in RAW.
> > 
> > RAW preview are mostly a small JPEG image embedded in RAW container. DK
> > extract this JPEG as well to render icon view thumbnails. It's very very
> > fast as no post processing is required.
> > 
> > Using RAW image data will be really slower to render large albums, and
> > will decrease DK performances. Even if libraw decoder can use fast RAW
> > extraction method without to much post processing, the democaising of
> > bayer
> > matrix will be a bottleneck.
> > 
> > Using sidecar can be a solution. Here i don't talk about XMP sidecar file,
> > but the .thm file coming with RAW file (Canon generate this kind of file,
> > as i know)...
> > 
> > But this will introduce another dysfunction, as THM file include also
> > metadata which do not correspond well with RAW metadata (incomplete).
> > THM cannot be used as metadata source, and this will increase the
> > complexity of metadata workflow.
> > 
> > Gilles Caulier
> > 
> > 2018-09-29 9:12 GMT+02:00 Andrew Goodbody <ajg02 at elfringham.co.uk>:
> >> On 29/09/18 07:55, Maik Qualmann wrote:
> >>> I did not understand the problem at first, but I can reproduce it with
> >>> my
> >>> Nikon. First of all, it is not a good idea to take a image in B&W
> >>> digitally.
> >>> There are many more ways to do it later, but for the JPEG the color
> >>> information is lost. There is currently no option in digiKam to specify
> >>> that a
> >>> thumbnail should be created from the RAW image. It uses the "fastest"
> >>> source
> >>> and that is the preview image. That was of course stored by the camera
> >>> in B&W.
> >>> 
> >>> Maik
> >> 
> >> Sounds like this could be a wishlist item for a 'sidecar-jpeg' which
> >> could be used for raw files to contain a preview image developed using
> >> the
> >> current edit settings for the raw file.
> >> 
> >> Andrew