[sane-devel] [ANN] unpaper 1.1 update

Jens Gulden mail at jensgulden.de
Sun Aug 28 19:16:38 UTC 2005

Janusz S. Bień schrieb:
>>- Resize to specific sheet sizes ('a4', 'letter', ...), zoom, stretch.
> Can this feature be used to actually reduce the resolution of scanned
> pages?

You can set the output sheet to a specific size with the desired dpi resolution, e.g.

--dpi 300 --size a4

In that case, the input images will automtatically be resized to fit best on the output sheet.
It is also possible to choose free sheet sizes, e.g. --size 15cm,20.125cm.

Or, if all input images already have an equal size, and the aspect ratio is ok, just use

--zoom 0.5 (600dpi->300dpi) or --zoom 0.666 (600dpi->400dpi)

to change the image size and thus the number of dots per inch. I think there is nothing more to 
changing the dpi of a .pbm-file than zooming it, because .pbm contains raw pixel data only and no 
meta-information on dpi. Whether the pixel data is interpreted as 600 dpi or 400 dpi, or whatever 
resolution, depends on the applications you use for further conversion to tiff, djvu, etc.


> I have large dictionary (15 volumes) scanned as 600 dpi TIFF files, you can
> have a look at it in DjVu format at
>         http://www.mimuw.edu.pl/polszczyzna/SGKPi/tomy.html
> On some stage of processing I would like to reduce resolution to 400
> or 300 dpi, to speed downloading paging for viewing, and also hoping
> it will fit on CD instead of DVD. My first idea was ImaMagic
> `convert', so I posted a query on ImagicMagic list
>         http://studio.imagemagick.org/pipermail/magick-users/2005-August/016021.html
> I have also posted a similar query on DjVu forum:
>         https://sourceforge.net/forum/message.php?msg_id=3313948
> To my surprise, I got no constructive answer. Is this task so difficult?
> Best regards
> Janusz
> P.S. The problem we discussed on the list in June seems to be solved by scanning
> the document again by a more careful and better qualified person. 

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