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May 2010

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2010.05.23 14:03 "How to descreen bilevel TIFFs into grayscale?", by Oliver Geisen
2010.05.23 21:38 "Re: How to descreen bilevel TIFFs into grayscale?", by Olivier Paquet

2010.05.23 21:38 "Re: How to descreen bilevel TIFFs into grayscale?", by Olivier Paquet

2010/5/23 Oliver Geisen <oliver.geisen@kreisbote.de>:
> i have bilevel TIFFs in high resolution. The contain screeningpatterns
> which represents gray level, just like you look at printed pictures with
> a magnifier glass.
>
> Now i want to calc previews from that. I tried to median the bits, but
> it still has artefacts on it. Is there a tool/way to descreen the
> rastered data to get better results?

Maybe I'm missing something but since your output is grayscale, it
should be as simple as resizing the image in gimp or some similar
tool. That resizing involves a filtering kernel to compute one low
resolution pixel from several high resolution pixels. The most basic
one would be to average the pixels together. This is often called a
box filter.

Olivier