Creating own RAW-Preview

[Sebastian Wagner-2]

Hey digikam-users,

I've small suggestion about the preview function in digikam (this
includes thumbnails, image-preview and slideshow, they use the same
function).

I have a Konica Minolta Dynax 7D and meanwhile I take my photographs in
RAW format. Now it's the case that digikam uses the RAW built-in preview
images. Of course, this means high-performance without pregenerating
thumbs (as it is done for JPEGs).

The problem that I have is the quality of these images. My camera stores
a 0.3mpix highly compressed preview-image (640x480, ~30kb), what means
that it is defineately the best for thumbnails, but even is enlarged for
the image-preview/diashow to nearly doube dimensions, so I have very
unsharp pictures with lots of compression-artifacts and, in addition to
this, very cold colours (much colder than the temperature stored in the
RAW-file).

I actually don't know, at how much camera models this problem is present
(I currently only know of D5D/D7D). For example, I know that Canon
stores an 1.5mp image (1526x1024, ~300kb), which has also very fine
colours and is defineately enough for preview and slideshow purposes.

So here is my suggestion:

Directly decompress RAWs would take too much time to be usable in
realtime. The solution for this would be a pregeneration of these
RAW-previews and store the relationships in a database. In addition to
this, the "last modified" date could be stored too to see whether the
thumb is still up to date or needs to be regenerated (But maybe this is
not needed since there is no possibility to change the picture-data so
the preview would be regenerated when simply set flags in the RAW-file).
Now not everybody needs this function (as I told you about the
Canon-RAWs), so it shouldn't be used automatically but in an extra
menu-point. I could imagine possibilitys like generating previews for
all images, all selected etc., set size and compression quality and
other things which are needful or necessary. To improve performance, the
RAW-integrated previews could still be used as thumbnails. In my point
of view, there is only one negative aspect in this solution: it needs
extra space (depending on how large and compressed the image is, about
+300-400kb). But this shouldn't be a problem today since there are hard
drives with hundreds of gigabytes capacity for less than 100$...

What I want to know from you:

- is there interest for such a feature?
- how "hard" do you see this problem?
- with which vendor do you have this problem (to get an overview about
the products that are affected)?

Best regards, Sebastian

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