agg and vector render options (was: Raster layer opacity)

[Daniel Calvelo Aros]

From: Bernhard Reiter <bernhard at intevation.de>
Sent: Tue, 29 Mar 2005 12:28:27 +0200

> Am 24. Mar 2005 um 23:57:48 schrieb Daniel Calvelo Aros:
> > BTW, has anyone looked at the Anti-Grain Geometry library
> > (http://antigrain.com)?
> 
> I did not, but when checking the website I found the proprietry
> license of General Polygon Clipper (GPC) appalling.
> Do you know how important gpc is for agg?
> If it is not important, why is it still in there?

AFAICT, GPC is only used for certain (vectorial) back-ends; otherwise, for
bitmap output, the equivalent operations are performed scanline-wise, outside
of GPC. So the horrid license should not be a major drawback.

> > How difficult would it be to use that for rendering to
> > a bitmap and copy this into a DC instead of using wxDC functions? 
> > Is the cost
> > of such a development worth the gain of antialiasing and transparency?
> 
> I cannot say, it would be interesting to see how wxWidgets people
> thing about their drawing capabilities and what they plan in this area.

Mmmmmh... Just thinking out loud: what do you think would be better a) having
some agg/gd/libart wxDC backend, or b) abstracting away wxDC in thuban so that
drawing backends could be switched? Maybe it's a stupid question, I haven't
studied the Renderer infrastructure.

> For www.skencil.org (former Bernhard Herzog's Sketch) I thought 
> about Cairo. Skenicl 0.7 uses libart, though this library did not 
> continue as strong as it started, so Cairo seems to be the future 
> within Gnome.

Yes, SVG seems to be the overall trend. I just read the OGC spec for SLD, and
its level of interoperation with SVG is almost scary.

> In my personal list of what I want to do with Thuban the antialiasing
> and transparency options are in the mid range. They look a lot nicer,
> but functionality counts first for most users.

Agreed. Although transparency to me is higher priority than antialising. It's
a feature that users might crave for.