# Re: Scanning and interpolation

becka@rz.uni-duesseldorf.de
Fri, 23 Apr 1999 20:09:03 +0200 (MEST)

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Hi !

> The best result is obtained by scanning in 1200 dpi and reducing the
> file with jpg compression, even though I had expected scanning in 300
> dpi to as good as 1200 dpi.

> SANE does no interpolation and will only deliver the optical resolution
> of the scanner. Is the apparent enhancement of the picture only an
> illusion?

Yes. Interpolation does not add any "inormation". It just places a grey pixel
between a black and a white one.

> It might be a good idea to introduce interpolation into SANE ?

No. It just adds useless data that carries no information to the output.

> Is the algorithms behind this free ?

I hope so. If someone patented this :

interpolated_pixel(between_pixel_1_and_pixel_2)=
( pixel_1*distance_to_1+
pixel_2*distance_to_2) /
( distance_to_1+distance_to_2 )

he is definitely insane.

> How is the interpolation done ? Close to the hardware or on the picture
> after scanning ? E.g. could it be done in GIMP ? -

Yes - choose "resample".

CU, ANdy

    --
    = Andreas Beck                    |  Email :  <andreas.beck@ggi-project.org> =

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