Re: Cairo-PNG

[Pierre <pie...@gm...>]

On 3/9/07, Ethan A Merritt <merritt@u.washington.edu> wrote:
> On Friday 09 March 2007 06:22, Pierre wrote:
> > Hello,
> >
> > On 3/9/07, Peter Danenberg <pc...@wi...> wrote:
> > > > My second concern is that we already have gd that does the work
> > > > quite well to export in jpeg/gif/png apart from not doing
> > > > antialiasing.
> >
> > As a side note, GD supports antialiased lines and polygon (without
> > transparency).
>
> Sorry to disagree,

Nothing to disagree, the AA support is limited, nothing new here :) Or
to be short, it works well only with simple (and single) lines.

> but in the context of drawing arbitrary curves
> with arbitrary line-widths (which is to say practically every line
> drawn by gnuplot) libgd through version 2.0.34 does not support
> antialiasing.

Yes, it is one of the case where the anti alias does not work well (I
should say does not work at all)..  Ellipse or circle (filled, arcs or
with thickness) will be in cvs in the next days. Filled polygon and
general ellipses will follow later. It will hopefully help to render
nicer shapes.

A temporary solution for the thick lines is to use the filled polygon
function, as long as you don't need transparency. I'm not sure it will
work well with polylines (it may draw twice the area between two
segments).

> > I'm working on the other drawing functions like the
> > filled ellipses or arcs as well as a an improved polygon function
> > (full transparency support as well).
>
> IMHO the most dramatic improvement would come from implementing
> an anti-aliased brushstroke.  That one change would by itself fix
> most of the aliasing artifacts seen in gnuplot png output.

Yes, but it is what cairo does and I don't think it is worth the
effort to re implement something like that in GD (it is not that
simple). However, if someone likes to implement something like that,
he will be more than welcome. I'll be happy to help (that's true for
any desired features or change).

--Pierre