Re: transparent lines and points

[Mojca M. <moj...@gm...>]

On Fri, Sep 4, 2009 at 02:31, Ethan Merritt wrote:
> On Thursday 03 September 2009 16:35:28 Mojca Miklavec wrote:
>> Hello,
>>
>> there are dozens of demos using transparent objects in gnuplot, but I
>> don't remember seing support for drawing transparent lines. Is that
>> possible?
>
> It is not possible.
> Transparency is currently implemented as a property of the fill style,
> not the color or linetype.  So only filled objects can make use of it.

Thanks. My suspects were true, but there have been quite some recent
changes, so I wasn't sure. (And this image is almost trying to
convince someone that transparency is doable with lines ...
http://gnuplot.sourceforge.net/demo_4.3/rgbalpha.1.png.)

> I think it would be straightforward to extend the newer rgb color support
> to full rgba support. That would get you transparent everything.
> But it would be a fair amount of work and touch every terminal driver.

I was (a bit naively) testing if
    withcolor rgba "#0000ff66"
was already working since I was last implementing color support in terminal.

> An intermediate possibility might be to have the solid point types
> honor the current fill style.

It's an interesting idea as a temporary hack, but something I would
vote against for a general implementation. For TeX (and possibly
others) the solid point types are no different than non-solid ones.

> Then you could at least have transparent
> circles, squares, and triangles.  I am not certain how much work that
> would be.  Again it would potentially touch every terminal driver that
> can handle solid points.

I'm fully aware of the fact that implementing transparency would mean
fixing almost every single terminal where one would require support
for that, yes.
But just honoring solid point types is a bad idea. I can imagine something like
    set style line 1 lc rgba "#0000ffcc"
or similar that would have equal influence on both lines and points.
Changing just solid point types is a bad idea.

Thank you,
    Mojca