[gs-devel] How to prevent interpolating artefacts when drawing transformed PDF

Chris Liddell chris.liddell at artifex.com
Sat Feb 16 16:32:04 UTC 2013


MuPDF isn't really my forte, nor is it really the subject for this mailing
list. You'd be better to address your questions on our IRC channel
(#ghostscript on freenode). Note that the developers are all around the
world, so you may not get an immediate respose, but the IRC channel is
logged, and we do check the logs.

Having said that, if you are using the mupdf applications (mudraw), you
might try using setting anti-aliasing bits to zero ("-b 0" on the command
line).

If that does what you want, but you are using the mupdf API, you could look
at how apps/mudraw.c handles the "-b 0" command line option when passing
stuff to the mupdf library.

HTH,

Chris


On 16 February 2013 13:27, Andreas Falkenhahn <andreas at falkenhahn.com>wrote:

> Hi,
>
> when I draw a PDF on a pixmap with a transformation matrix enabled, I face
> the problem
> that there are white artefacts around the page because MuPDF seems to
> interpolate the
> bordering pixels of the page with the pixmap background which is all
> white. See here
> for a screenshot that shows what it looks like:
>
> http://www.falkenhahn.com/tmp/mupdf_artefacts.png
>
> Is there any way to get rid of these artefacts? I would like to have
> pixmap that I can draw
> to any arbitrary background (e.g. red, green, yellow colored...) but I do
> not know the color
> of the background at the time of calling fz_run_page(). Thus, I somehow
> need to prevent MuPDF
> from interpolating pixels by blending with the current pixmap background
> color. Instead, it
> should just write the raw alpha blending values into the pixmap so that
> the pixmap can be
> smoothly drawn to any surface later.
>
> Does anybody know how this could be achieved?
>
> Thanks!
>
> Andreas
>
> _______________________________________________
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> gs-devel at ghostscript.com
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>
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