[Octave-bug-tracker] [bug #42543] transparent surface using facealpha is not working

[Rik]

Update of bug #42543 (project octave):

              Item Group:       Inaccurate Result => Incorrect Result       
                  Status:               Need Info => Confirmed              
        Operating System:       Microsoft Windows => Any                    

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Follow-up Comment #8:

The issue seems to be that not many gnuplot terminals actually support
transparency.  "help transparent" from within gnuplot 5.0.3 returns


      terminal   solid pattern    pm3d
       --------------------------------
       gif           no     yes      no
       jpeg         yes      no     yes
       pdf          yes     yes     yes
       png    TrueColor   index     yes
       post          no     yes      no
       svg          yes      no     yes
       win          yes     yes     yes
       wxt          yes     yes     yes
       x11           no     yes      no


In particular, the eps terminal does not seem to support transparency.  This
is an issue for Octave because printing generally relies on first creating a
.eps file, and then using Ghostscript to transform from eps to just about
anything else.

There are several workarounds.  First, use a terminal that supports
transparency such as "svg".  Second, go through the cairo series of terminals
if they are supported on your computer.


print -dsvg file.svg
print -dpngcairo file.png
print -dpdfcairo file.pdf
print -depscairo file.eps


I've added Dan Sebald to the CC list since he is the export on the gnuplot
interface.  A longterm option for Octave might be to switch from using the
"eps" terminal to the "epscairo" terminal to generate the initial eps file. 
With that change, the rest of the backend plotting routines would work just
fine.



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