Sigma raw files for newer cameras eg Sigma SD1 are not supported by dcraw or digikam. However these files contain embedded jpeg files for previewing (which are already used to get the image thumbnails); It would be useful if these embedded jpegs could also be used for previewing the image to look at details that are visible from the thumbnail.
Steps to Reproduce:
1. click on sigma raw image (x3f) to preview.
image shows up looking like a bunch of noise (libkraw does not decode the image correctly).
a reduced size preview of the image should appear.
actually I wouldn't mind if this behaviour was changed for all sigma cameras. DCRaw has a hard time with the files it does support (the jpeg previews usually look better than what it produces).
Can you provide a sample file for testing?
We don't use dcraw for RAW handling, but libraw (http://www.libraw.org)
Sound like a wish for libraw as well.
Please provide a sample file for Alex (libraw author)
Also, give us which libraw you use ? Go to Help/Components Info for details.
Marcel : We don't use Exiv2 for raw preview extraction. Right or i'm wrong ? Both are possible (exiv2 or libraw). Typically libraw has a better support of raw file preview than exiv2
We use exiv2, it gives us a very clean API, we see which previews are available and at which size, and can decide before loading anything if the preview is large enough or too small etc.
if a raw file type mime is not supported by Exiv2, libkdcraw must be used instead. libraw from libkdcraw support X3F. I suspect that X3F is not suported by Exiv2...
Git commit 14e711ba5d7146fb15d90a9609bfdbfda6dff8c4 by Marcel Wiesweg.
Committed on 19/06/2012 at 20:05.
Pushed by mwiesweg into branch 'master'.
Use libraw as a fallback for RAW preview loading in case exiv2 fails.
Some cleanups and code reuse in the code.
M +55 -30 libs/threadimageio/previewtask.cpp
The patch enables usage of libraw preview loading. Note I don't have recent .x3f and none was provided here, thus waitingforinfo as I cannot test.
I thought I had added one - but at ~40mb seems to be too big for the tracker - I have published the fire here http://ubuntuone.com/0MiyU3Og5lyaXWoKDtQlSN
Indeed, Exiv2 fails at this image, but with this fix, the embedded JPEG is extracted by dcraw.