Hello Ivom,
Width and height have been removed recently in trunk as the image
dimensions are automatically read from the image.
In the 0.7 branch they still exist but do not scale the image, as they
should (rather they crop). We are planning support for this, but it
has not yet been implemented.
We are considering whether to simply add a single option to scale the
image or keep the width/height to allow for scaling in each dimension.
I can see value to both approaches. What would you find more useful/
intuitive?
Best,
Dane
On Jan 5, 2010, at 3:26 PM, ivom wrote:
> Hi,
>
> Running with mapnik 0.7 in python (generate_image.py). I am
> attempting to
> have pointsymbolizers use an image and scale it depending on an
> external
> value. So depending on the external value the image will change in
> size.
>
> When I attempt this by manually editing a style-rule-filter combo
> everything looks as intended:
>
> <snip>
> <Rule>
> <Filter>(([absaccelvalue]>1500))</Filter>
> <PointSymbolizer
> file="/home/ivom/openstreetmap/mapnik/symbols/bus_stop_small.png"
> type="png" width="8" height="8" allow_overlap="yes"></PointSymbolizer>
> </Rule>
> <Rule>
> <Filter>(([absaccelvalue]<1500) and
> ([absaccelvalue]>600))</Filter>
> <PointSymbolizer
> file="/home/ivom/openstreetmap/mapnik/symbols/bus_stop_small.png"
> type="png" width="2" height="2" allow_overlap="yes"></PointSymbolizer>
> </Rule>
> </snip>
>
> I want fine-grained control programatically, changing the scale factor
> depending onthe filter result. More elegant and easier to maintain.
>
> So depending on the filter-result I attempt to scale the
> PointSymbolizer
> image. When I do this, the x- and y-values I think I introduce
> seemingly
> only offsets the PointSymbolizers image, but not it's scale/size.
>
> <snip>
> s=Style()
> for i in range(300,800,100) :
> sym = PointSymbolizer(
> "/home/ivom/openstreetmap/mapnik/symbols/bus_stop_small.png",
> "png",i,i)
> sym.allow_overlap=True
> sym.opacity=.5
> r=Rule()
> r.symbols.append(sym)
> r.filter = Filter("[absaccelvalue] >"+str(i)+" and
> [absaccelvalue] <
> " + str(i+100))
> s.rules.append(r)
> </snip>
>
> To illustrate the problem, have a look at the following two images
>
> 1 (ok) http://dl.dropbox.com/u/307509/shifted-snip.png
>
> and
>
> 2 (weird offsets) http://dl.dropbox.com/u/307509/scaled-snip.png
>
> Where I have drawn a set of gps trace dots where the image size should
> vary with a dependent value.
>
> From the api docu:
> http://svn.mapnik.org/trunk/docs/api_docs/python/mapnik._mapnik.PointSymbolizer-class.html
> I even get another idea of what the constructor and the accessors
> are able
> to accept. For what I see the width and height are not there at all as
> parameters.
>
> This puzzles me today. Kind regards,
> Ivo
>
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