[FWTools] Re: Style usage?
dmorissette at mapgears.com
Fri Dec 28 08:50:28 EST 2007
Stefan Keller wrote:
> 1. Is there also a concept and a way to change style output in an
> ogr2ogr call, e.g. for KML?
I don't think ogr2ogr supports "changing" the style assigned to a given
feature or assigning new styles to features, but when translating
between formats that support styles (e.g. TAB, MIF and DGN) then the
styles are maintained as much as possible.
With respect to KML, last time I checked I don't think the KML driver
supported styles, so the answer is no, at the moment it is not possible
to control the style of the features written to KML output (but
technically that's feasible and could be implemented someday).
> 2. Regarding the style concept perhaps it would be helpful to mention
> similarities to SLD and eventually also to Mapfile symbols (if there are
The concept of assigning rendering rules to geometries is shared in both
cases but that's about it. The terminology (pen/brush/etc vs
symbolizers) and encoding (compact text strings vs verbose XML) are
SLD also supports building up classifications using filter encoding
which is not part of the OGR style concept.
Why did OGR invent its own encoding instead of reusing SLD? Mostly
because the OGR style encoding predates the days when SLD became well
known (to me anyway) and widely used. But even if we were to do this
again today I'm not sure if we would opt for a verbose XML encoding...
we'd probably spend a lot of time debating the performance issues vs the
benefits of interoperability with SLD.
BTW, this question would really belong on the gdal-dev list, so I have
cross-posted my reply to gdal-dev (and ask that further replies be sent
only to gdal-dev).
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