Transparent fillstyle for boxes with postscript

Michael Hofmann

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Apr 13, 2011, 10:14:46 AM4/13/11

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Hi,

the postscript terminal (version 4.4 patchlevel 0) does not seems to be
able to create "boxes" with transparent fill style (pattern or solid).
With "filledcurves" transparency works for the graph, but not for the
legend.

Is this a bug or a missing feature of the postscript terminal?

Additionally, I would expect that the look of the filling for a terminal
is independent from object that is filled. However, for postscript,
there seem to be a difference between rectangles and polygones.

The following plot shows the problem:

set term postscript eps solid
set output "test.eps"

plot x/((x>=0)?1:0) w boxes fs solid 0.4 lc rgb "black", \
x/((x>=0)?2:0) w boxes fs transparent solid 0.4 lc rgb "black", \
x/((x>=0)?4:0) w boxes fs transparent pattern 4 lc rgb "black", \
x/((x<=0)?1:0) w filledcurve y1=0 fs solid 0.4 lc rgb "black", \
x/((x<=0)?2:0) w filledcurve y1=0 fs transparent solid 0.4 lc rgb
"black", \
x/((x<=0)?4:0) w filledcurve y1=0 fs transparent pattern 4 lc rgb
"black"

unset output

Best regards,
Michael

sfeam

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Apr 13, 2011, 2:13:42 PM4/13/11

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Michael Hofmann wrote:

> Hi,
>
> the postscript terminal (version 4.4 patchlevel 0) does not seems to be
> able to create "boxes" with transparent fill style

The PostScript language itself does not support transparency.
Can you use PDF instead?

If not, you could try converting PDF output to PostSCript later.
Some (most?) conversion programs will dummy up the effect of transparency
by rendering the net color of each pixel in the PDF version rather than
reproducing the multiple, perhaps transparent, operations that created it.

Michael Hofmann

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Apr 14, 2011, 3:22:57 AM4/14/11

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Am 13.04.2011 20:13, schrieb sfeam:
> Michael Hofmann wrote:
>
>> Hi,
>>
>> the postscript terminal (version 4.4 patchlevel 0) does not seems to be
>> able to create "boxes" with transparent fill style
>
> The PostScript language itself does not support transparency.

OK, but why *is* transparency working for "filledcurves" with
PostScript, but *not* for "boxes"? I would expect it works for both, or
for none.

Michael

sfeam

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Apr 14, 2011, 11:59:34 AM4/14/11

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Michael Hofmann wrote:

The same PostScript commands are used for both plot styles.
Perhaps you are noticing a difference between pattern-fill and solid-fill?

Michael Hofmann

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Apr 15, 2011, 9:35:27 AM4/15/11

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I noticed that transparent pattern-fill with filledcurves works and
wondered why transparent pattern-fill with boxes fails. Transparent
solid-fill does not work for both.

However, pattern-fill with filledcurves in PostScript looks very
different than pattern-fill with boxes. So I guess these are two
different routines.

Michael

sfeam

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Apr 15, 2011, 12:16:43 PM4/15/11

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Michael Hofmann wrote:

I suspect that the difference you see is an artifact of whatever
viewer you are using to look at the PostScript. Most viewers that
I know of handle pattern fill in rectangular areas OK, although you
may have to disable anti-aliasing. But many/most of them do a bad
job in non-rectangular areas. More specifically, they do a bad job
of matching the pattern origin in adjoining tiles of a tiled region.

It may be that very recent versions of PostScript support some sort of
higher-level command to control the rendering of adjoining pattern-fill
areas. If so, that would be useful - but that's unknown territory for me.

Ethan