Re: Layer compositing and erasing

On Sep 17, 2010, at 2:10 PM, Lars Ahlzen wrote:

> On 09/16/2010 06:23 PM, Michal Migurski wrote:
>> On Sep 16, 2010, at 11:28 AM, Lars Ahlzen wrote:
>> 
>>> In my dreams, you could specify erasing with something like:
>>> 
>>> <PolygonSymbolizer> <CssParameter
>>> name="fill">transparent</CssParameter> </PolygonSymbolizer>
>>> 
>>> and
>>> 
>>> <TextSymbolizer name="..." fill="#000" halo_fill="transparent"
>>> halo_radius="2" />
>>> 
>>> to get nice "cutouts" for halos and polygons in a semi-transparent
>>> map tile.
>>> 
>>> AFAIK, drawing-wise, setting the destination alpha is a relatively
>>> straightforward operation with both AGG and Cairo.
>> 
>> 
>> Don't you just want a mask, and the possibility of nesting layers and
>> groups of layers?
> 
> Well, anything that can produce the results I want. :)
> 
> This just seems like the simplest and most efficient way. Or did you
> have some specific solution in mind that I may have overlooked?

I guess I'm just trying to figure out the easiest, most Photoshop-like way of representing these
operations. So far my personal skin in the game is this:
	http://tilestache.org/doc/TileStache.Goodies.Providers.Composite.html

...which is just taking shape slowly. I recently read the Porter Duff paper and I think I've got some work to
do. =)

-mike.

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michal migurski- mike@...
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