[Poppler-bugs] [Bug 25268] image scaling is ugly / not antialiased in Evince 2.28

[bugzilla-daemon at freedesktop.org]

http://bugs.freedesktop.org/show_bug.cgi?id=25268





--- Comment #18 from Carlos Garcia Campos <carlosgc at gnome.org>  2010-02-25 01:02:54 PST ---
(In reply to comment #17)
> FWIW, in my opinion, poppler should just always interpolate, regardless of what
> the Interpolate flags says. 
> 
> Reasons:
> 
> - It is clearly what acroread does.

really? With the test cases attached to bug #9860 acroread only shows smoothed
graphic for the interpolate=true case. Maybe there's a configuration option in
acroread to enable/disable it, I haven't found it though.

> - From a theoretical perspective, you can't upscale an image without
> interpolating. It doesn't make sense, because interpolation is what upscaling
> _is_.
> 
> - By using CAIRO_FILTER_NEAREST, poppler is still interpolating, it is just
> using a poor interpolation filter.
> 
> - The PDF spec says that Interpolation is turned off by default for performance
> reasons, but that is kinda bogus because a PDF file can't know the performance
> characteristics of an output device.
> 
> - It also says that the interpolation filter is not defined even when it is
> turned on, so a PDF producer can't rely on this flag for any kind of accurate
> output.
> 

Ok, so maybe we could try to find a smarter way to select the filter depending
on the image resolution, as Jean-François proposed. 


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