Re: Fwd: [Gnuplot-developers] [ gnuplot-Patches-1651015 ] Cairo-based PDF terminal

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

On Monday 12 March 2007 11:03, Petr Mikulik wrote:
> > where the operator "g" is defined in the page header based on
> > the current palette.  In other words, the color mapping is done
> > by the postscript interpreter, not by gnuplot.  I believe the
> > reason for this was simply to make the output file shorter.
>=20
> Plus two more reasons:
>   - replace the color - gray by a simple switch in the header

%% Boolean flag Color (user-editable) used to toggle palette;
%% Switch between rgb color and grayscale using ntsc conversion
\C  {Color {setrgbcolor} {ntsc setgray} ifelse} def

>   - possibility to change the color palette

By editing the PostScript file?  That sounds like a very unusual
thing to do.  Can you give an example?

> > I'm cc'ing this to Petr, who may want to comment on whether
> > there are cases where weak optimization (factor of 2 at best)
> > is still useful.=20
>=20
> It is of factor 3:
> 	.123
> 	.123 .123 .123
> thus a lot of KB's more to add into the file or (LaTeX) paper.

I think it's a factor of slightly less than 2:

Currintly routine save_space(gray) returns a 4-digit float
to be printed as "%.4g g"
       .1234 g 	  % 7 characters for 4-digit gray scale

We work internally with 24bit RGB colors in most places, so
if we were to switch to an RGB-based postscript output it could
logically be
	/C {255 div 3 1 roll 255 div 3 1 roll 255 div 3 1 roll
            setrgbcolor} def
yielding
	RRR GGG BBB C   % 13 characters for 24-bit color=20


> > So there are two questions:
> >=20
> > 1) Is this really worth doing in PostScript?
>=20
> Definitely.
>=20
> > 2) If it is worth it for PostScript, does that mean it is also
> >    worth doing for pdf?
>=20
> No, pdf is not intended to be edited.

PDF is mostly just marked-up PostScript which is then compressed.
Any feature which is useful in PostScript should also be available
in PDF.  Which brings up a good point...

Even aside from Timoth=E9e's new pdf driver, wouldn't it be a good
idea to offer the same user-editable flags at the start of gnuplot's
PDF output that we offer for the PostScript output?  That would give
the user the same ability to tweak the *.pdf file that they already
have for the *.ps files.


=2D-=20
Ethan A Merritt            Courier Deliveries: 1959 NE Pacific
Dept of Biochemistry
Health Sciences Building
University of Washington - Seattle WA 98195-7742