Review Request 113397: RAW preview in gwenview

[Martin Kyral]

> On Nov. 5, 2013, 5:04 p.m., Aurélien Gâteau wrote:
> > lib/thumbnailprovider/thumbnailgenerator.cpp, line 128
> > <http://git.reviewboard.kde.org/r/113397/diff/6/?file=206503#file206503line128>
> >
> >     It looks to me like the new code is never going to use the embedded thumbnail, this could have a bad impact on performance.
> 
> Martin Kyral wrote:
>     Yep, it seems so. However, using the embedded small thumbnail has some serious drawbacks:
>     
>     1) there's no particular function in libraw (nor kdcraw), fetching the small size thumbnail (unpack_thumb() returns the large preview if present)
>     2) not every raw file contains the small thumb
>     3) the thumbnail (if any) is always 160x120 (4:3) while majority of the raw-enabled cameras shoot 3:2 pictures. That leads to ugly black stripes along the longer sides of the thumbnail.
>     4) the thumbnail view shows the 160x120 as a resolution of the image (not sure if this can be overriden by exif data and how)
>     
>     I tested various formats with the following results:
>     
>     1) canon cr2 loads nice big thumbnails even without any additional support in gwenview/dolphin. It seems that it behaves as JPEG when loaded which is pretty the same as loadEmbeddedPreview does.
>     2) nikon nef, pentax dnf, leica dng has ugly back stripes on the longer sides, reported size 160x120px, seems poor when user "zooms" the thumbnails
>     3) sony arw, pentax pef, olympus orf, nikon nrw, fuji raf doesn't seem to contain the small thumb at all
>     4) nokia dng loads as tiff, full size, but dark and with screwed colours (violet - green)
>     
>     Now, all the images supporting the embedded JPEG preview are behaving just as JPEG files with the very little overhead caused by need of extracting the JPEG data from the raw file first (which is instant). From what I see the performance is quite good (comparable to JPEG), there's just the fact, that some of the files have really huge dimensions (like 7360x4912 /36mpx/ from nikon d800).
>     I recently added experimental support for loading downsampled preview from the actual raw data when the embedded preview fails for whatever reason and there's performance drop in such cases, but I consider it better than no support at all. Having this, gwenview can display really everything! :)
>     
>

fixed in v8


- Martin


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On Nov. 7, 2013, 3:03 p.m., Martin Kyral wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> http://git.reviewboard.kde.org/r/113397/
> -----------------------------------------------------------
> 
> (Updated Nov. 7, 2013, 3:03 p.m.)
> 
> 
> Review request for Gwenview and Aurélien Gâteau.
> 
> 
> Repository: gwenview
> 
> 
> Description
> -------
> 
> This is a review of patch enabling raw support in gwenview. It uses KDcraw to extract the embedded jpeg preview (most of the raw formats contain it for the purposes of quick viewing the photos on the camera display) so it is fast, implementing was quite easy and theoretically it enables gwenview to support everything dcraw supports (practically we need to test more formats). The patch does not perform demosaicing and I don't think it shall - digikam, darktable or rawtherapee are much more suited for developing the 'digital negatives'.
> 
> The patch fixes BZ#158788
> 
> The patch enables support for Nikon NEF and NRW formats, Canon's CR2, Pentax PEF, Sony ARW and Adobe DNG. If you want to try another format, just adding it's MIME type to the list in lib/mimetypeutils.cpp shall be enough.
> 
> The patch as is contains just the basic functionality (generating proper thumbnails and viewing the raw images incl. EXIF metadata), but it is well usable. However, there is still a lot of stuff to do (see the commit message in the patch) so I'd appreciate any help.
> 
> 
> Diffs
> -----
> 
>   CMakeLists.txt 4dafb7e 
>   lib/CMakeLists.txt c6ffe14 
>   lib/document/loadingdocumentimpl.cpp fbad8ff 
>   lib/gwenviewconfig.kcfg 231fd5e 
>   lib/mimetypeutils.cpp 546346f 
>   lib/thumbnailprovider/thumbnailgenerator.cpp 8b98904 
> 
> Diff: http://git.reviewboard.kde.org/r/113397/diff/
> 
> 
> Testing
> -------
> 
> Tested on some sample raw files taken from the camera reviews on http://www.photographyblog.com/ and bunch of my own photos. Nikon (tried D50, D70s, D90, D800 and Coolpix P7000), Canon (tried 7D, 5D Mark3 and 6D) and Pentax (K-X, K30) have the preview full-res, while Sony raw files (A900, A850, A58, Nex 3, Nex 6) have only 1616x1050.
> 
> 
> Thanks,
> 
> Martin Kyral
> 
>

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