[GRASS-dev] PNG driver - slow?

[Jachym Cepicky]

Thanks, Glynn, I just used it in new GUI function - you select objects
in attribute table and they are displayed with d.vect col=yellow
width=3 in map display..

It works  great, thanks again!

jachym


2007/4/6, Glynn Clements <glynn at gclements.plus.com>:
>
> Glynn Clements wrote:
>
> > > export GRASS_PNGFILE=/tmp/pokus.png
> > > export GRASS_RENDER_IMMEDIATE=TRUE
> > >
> > > time d.vect map=soils at PERMANENT
> > > real    0m0.197s
> > > user    0m0.166s
> > > sys     0m0.019s
> > >
> > > time d.vect map=soils at PERMANENT color=yellow fcolor=yellow cats=32 width=3
> > > real    0m13.767s
> > > user    0m13.611s
> > > sys     0m0.098s
> > >
> > >
> > > Why is the second case so slow? Is it a bug in PNG driver? What can I
> > > do, so it is rendered faster?
> >
> > My guess is the width=3.
> >
> > The "thick line" code in the PNG driver is a truly awful hack (see
> > store_xy() in lib/pngdriver/Draw_line.c).
>
> I've replaced this with a more reasonable implementation.
>
> However, note that the PNG driver doesn't have a proper polyline
> implementation; it just draws each segment as a separate line. This is
> fine for single-pixel lines, but for thicker lines the lack of proper
> joins may be noticeable.
>
> --
> Glynn Clements <glynn at gclements.plus.com>
>


-- 
Jachym Cepicky
e-mail: jachym.cepicky gmail com
URL: http://les-ejk.cz
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