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

Andreas Falkenhahn andreas at falkenhahn.com
Sat Feb 16 13:27:38 UTC 2013


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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