[digiKam-users] How to rebuild RAW thumbnails?

[Maik Qualmann]

The change is small, we still have time to test it until the final release. 
For normal NEF files, there is no performance degradation. Even color images 
in dark or with a closed lens lid are not identified as a grayscale image. Of 
course, loading a grayscale image takes a few seconds. Sepia-effect images are 
probably not recognized as a grayscale image.

https://cgit.kde.org/digikam.git/commit/?
id=e0d01f6283bde9cd9d78a11239d82234fc96a136

Maik

Am Mittwoch, 3. Oktober 2018, 18:28:35 CEST schrieb Cirrus:
> Wow. That would be great.  :-)
> 
> Imho, the thumbnail should reflect what the raw contains rather than what
> the camera spit out as a secondary product.
> (I'm not sure why Ricoh went with the opposite.)
> 
> On Wed, Oct 3, 2018, 11:34 Maik Qualmann <metzpinguin at gmail.com> wrote:
> > 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