[cairo-bugs] [Bug 63302] Mask problem in pdf

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Mon Oct 19 01:32:49 PDT 2015


--- Comment #17 from Adrian Johnson <ajohnson at redneon.com> ---
Created attachment 118974
  --> https://bugs.freedesktop.org/attachment.cgi?id=118974&action=edit
test case fixed to turn off interpolation

The cairo pdf backend embeds images exactly as they are. There is no resampling
done. The interpolation is being done by the pdf viewer. You can see the
embedded images using pdfimages.

Attached is an updated version of the test case that causes the interpolate
flag in the embedded image to be set to false. The problem is pdf viewers may
ignore this flag. This can be seen in evince where at higher zoom levels the
image is not interpolated and the gray pixels disappear. At lower magnification
evince will turn on interpolation to match Adobe Reader behavior.

There really isn't anything that can be done in cairo. The cairo pdf backend is
creating a pdf that reproduces the cairo drawing operations supplied to it. It
is up to the viewer how it is rendered.

Possible (untested) workarounds:
- Use a higher resolution image
- Ensure the color image is larger than the mask.

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