Re: Separating line color and dot/dash pattern

[Ethan M. <merritt@u.washington.edu>]

On Saturday 05 February 2005 12:25 pm, Harald Harders wrote:
> On Sat, 5 Feb 2005, Ethan Merritt wrote:
>
> > - The obvious extension is to add a keyword "{dt|dashtype} <n>".
> >   In the context of setting a line style, the command would be
> >     set style line <tag> dt <N> lt rgb "#aabbcc"

> I think the keyword 'colour' is more clear because it tells what it
> changes. And at the moment, linetype changes both color and dashtype in
> many cases which should be preserved for compatibility.
> Set dashtype to <N> and color to RGB value of aa, bb, cc:
>   set style line <tag> dashtype <N> color rgb "#aabbcc"

But is it really more clear?  Remember that currently the
"line style" also includes the point type and point size.
Is "colour" to apply to both the line and the points, or is
it specifically the line colour?

And I think there are compatibility issues. Consider the command
	plot "foo" with linespoints dashtype <n> color rgb "red"

What exactly do you expect to happen to the points?
And what should happen on a terminal that cannot set rgb colors?

> Escpecially for postscript there is a difference between cmyk and rgb
> (and hsb) colours depending on the output device.

So?  That's a totally orthogonal issue. Anything that depends on the
eventual PostScript output device is clearly out of gnuplot's control.
If you are concerned to have an hsv option, this could either be created
as a parallel option to rgb, or else we could define a user-accessible
string-valued function  hsv2rgb(H,S,V)  that returns "#RRGGBB". E.g.
	set style line 1 lt rgb hsv2rgb(H,S,V)
Hmmm. Actually, I think you could do that anyhow right now just by
loading a script that defined such a funciton. 

> > - A surprising number of terminal types already support dashed lines:
> >   But I suspect that other than the ones piggybacking on post.trm
> >   they all disagree about specific dot/dash patterns.
>
> Yes, I think, all terminals should be harmonized.

Good luck. There is no guarantee that any particular terminal device
is capable of a particular dash style.  We haven't even reached a 
point where all terminals agree on colors! (Nor do I necessarily
think they should - what looks good on the screen may not look good
on paper).


-- 
Ethan A Merritt
Biomolecular Structure Center
University of Washington 98195-7742