[Digikam-devel] Patch: fix automatic correction of lens chromatic aberration

[Matthias Welwarsky]

On Monday 09 March 2009 11:30:27 Andi Clemens wrote:
> I will take a look it the patch now...

I've taken another look into it, seems its not complete yet. Geometry and 
distortion correction also need subpixel access, and I've found that it 
doesn't work any more if I check "16 bits color depth" in the "Raw Conversion" 
settings.

>
> Andi
>
> On Sunday 08 March 2009 19:51:12 Gilles Caulier wrote:
> > Matthias,
> >
> > Thanks a lots. this patch solve a task from my TODO list.
> >
> > This patch is a good candidate to go to 0.11 development branch and, if
> > it doesn't break i18n, in 0.10 (trunk) before finale release.
> >
> > Marcel, Andi, can you check this patch for me and guide Matthias on the
> > right way. I'm very busy here to prepare my evening classes presentation
> > for next Wednesday. To test, just use these pictures :
> >
> > http://digikam3rdparty.free.fr/TEST_IMAGES/LENSFUN/
> >
> > Thanks in advance.
> >
> > Gilles Caulier
> >
> > 2009/3/8 Matthias Welwarsky <matze at welwarsky.de>
> >
> > > Hello,
> > >
> > > the attached patch fixes CA correction in the lens auto-correction
> > > tool. The fix
> > > consists of two parts:
> > > 1.) set Alpha component of corrected pixel to "fully opaque", otherwise
> > > corrected image is not visible (trivial)
> > > 2.) Implement sub-pixel interpolation in class DImg, necessary for CA
> > > and CI
> > > correction with lensfun.
> > > There are two new pixel color accessor functions: getSubPixelColor()
> > > and getSubPixelColorFast(). The first one uses Lanczos interpolation to
> > > compute subpixel colors, the second one bilinear interpolation. Lanczos
> > > yields better
> > > results, but is a lot slower than bilinear. Before using
> > > getSubPixelColor(),
> > > prepareSubPixelAccess() needs to be called to precompute the Lanczos
> > > kernel.
> > >
> > > Lanczos implementation was adapted from ufraw, Bilinear was implemented
> > > according to Wikipedia description.
> > >
> > > I would be happy to hear comments on how to optimize the computation,
> > > it's probably not optimal yet.
> > >
> > > regards,
> > >         matthias
> > >
> > > _______________________________________________
> > > Digikam-devel mailing list
> > > Digikam-devel at kde.org
> > > https://mail.kde.org/mailman/listinfo/digikam-devel
>
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