[GRASS-user] translucency and svg output

[pete davidson]

On Wed, Mar 24, 2010 at 7:49 PM, pete davidson <caitifty at gmail.com> wrote:

>
>
> 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.
>

And then we discover that the 'svg' produced by cairo using the above script
is actually just a png in an svg wrapper..  At least for my particular
install of Grass.  That's frustrating.  Ahh well, back to the drawing board.

Peter
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.osgeo.org/pipermail/grass-user/attachments/20100324/6d3600da/attachment.html