[GRASS-user] translucency and svg output

pete davidson caitifty at gmail.com
Wed Mar 24 22:49:46 EDT 2010

On Wed, Mar 24, 2010 at 7:42 PM, Glynn Clements <glynn at gclements.plus.com>wrote:

> pete davidson wrote:
> > I'm producing maps in svg format using the cairo driver and d.out.file.
>  One
> > thing I'd really like to be able to do is set one or more of the vector
> > layers to be partially translucent.  After rummaging through this list,
> I'm
> > beginning to wonder if its possible at all, since translucency in the
> guis
> > seems to be handled by g.pnmcomp, but perhaps someone with more
> experience
> > knows a way to do it.
> It isn't. The graphics API doesn't support an alpha component.
> Apart from anything else, it can't easily be implemented for
> PostScript output, as PostScript doesn't support translucency. Faking
> it with patterns is possible, but it starts getting complicated if you
> want more than one translucent layer.
> > The only workaround I've managed to find so far is to export each layer
> as
> > an individual svg, then use something like inkscape to rejoin them,
> setting
> > the translucency/transparency of each layer as I do it.  Which is fine
> for a
> > map with only a few layers, but gets tedious when dealing with maps with
> > dozens of layers.
> SVG is XML, so it shouldn't be especially hard to automate the process
> using generic XML-processing tools.

Ohh, I hadn't thought of editing the svg/xml directly.  Thanks for the
suggestion, I'll see what I can achieve from there.


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