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Re: does facealpha work?

From: Francesco Potortì
Subject: Re: does facealpha work?
Date: Fri, 25 Jul 2014 19:59:08 +0200

>On Jul 25, 2014, at 10:30 AM, Francesco Potortì <address@hidden> wrote:
>>> I have tried fill() and 'FaceAlpha" property, but cannot obtain the
>>> results I want.  By changing facelpha i can change the colour, which
>>> becomes paler, but not transparent, as the filled areas below cannot be
>>> seen.  I use the gnuplot backend.
>>> Is there anything obvious that I should know?  Do I need to provide an
>>> example or is this a known problem?
>> Here is an example:
>> hold on
>> p1 = patch([0 0 2], [0 2 1], "r")
>> p2 = patch([2 2 0], [0 2 1], "g")
>> hold off
>> This draws two partially overlapping triangles of different colours, as
>> expected.  Now I set the facealpha property on both to make them
>> partially transparent:
>> set (p1, "facealpha", 0.2)
>> set (p2, "facealpha", 0.2);
>> Both colours become less saturated, but they remain opaque.  Is this a
>> bug?
>I don't think is facealpha is supported by Octave for the gnuplot
>toolkit. If my recollection is correct, the problem is that Gnuplot
>doesn't support transparency for postscript output, and Octave derives
>nearly all output from an eps-file.

Yes!  If I print to svg it shows the correct transparency!


Unfortunately I cannot try fltk because of a bug somewhere that popped
up after some upgrade, I suppose.  I will post a bug report when I come
back from vacations :)

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