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

[Gilles Caulier]

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
>
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>
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