Hi Roger,
Here is my guess...
Styles (and Rules) are only evaluated at mapnik.render(), so remove_style() and
append_style() do nothing at run time, just the last one, as you explain, will
have some effect.
# No-warranty snippet ;)
# Create just one style
s = mapnik.Style()
for feature in PosQuery:
....
r = mapnik.Rule()
....
# Keep adding different rules to the style
s.rules.append(r)
# m.remove_style('selected')
# append the style once (outside the loop)
m.append_style('selected',s)
Good luck!
Manel
________________________________
De: [email protected]
[mailto:[email protected]] En nombre de Roger Barrette
Enviado el: jueves, 09 de junio de 2011 19:59
Para: [email protected]
Asunto: [Mapnik-users] Problem appending multiple symbols to map
Hi all, I just started working with Mapnik the other day. I have taken one of
the demos and modified it in an attempt to iterate through a database of
country names, and then simply change their color to red if they are present in
the table. the problem is that, although it appears to iterate through all of
the countries, the only one that gets 'labeled red' is the last on in the loop.
The code is as follows:
(Select some data from a mysql database....)
MappingLines = cursorM.fetchall()
m = mapnik.Map(800,300)
mapnik.load_map(m,'c:\\IVVSL\\Results\\populationb.xml')
countries = m.layers[0]
ds = countries.datasource
countries.styles.append('selected')
featureset = ds.all_features()
PosQuery = []
for Mline in MappingLines:
critFilter = ("[NAME] = '%s'")%Mline[1]
criteria = mapnik.Filter(critFilter)
queryset = [f for f in featureset if criteria.passes(f)]
try:
PosQuery.append(queryset[0])
except:
continue
for feature in PosQuery:
m.zoom_to_box(feature.envelope())
m.zoom(1)
name = str(feature.attributes['NAME'])
print 'Matched %s...' % name
feature_filter = mapnik.Filter("[NAME] = '%s'" % name)
s,r = mapnik.Style(),mapnik.Rule()
r.symbols.append(mapnik.LineSymbolizer(mapnik.Color('darkorange'),3))
r.symbols.append(mapnik.LineSymbolizer(mapnik.Color('yellow'),2))
r.symbols.append(mapnik.PolygonSymbolizer(mapnik.Color('red')))
t = mapnik.TextSymbolizer('NAME', 'DejaVu Sans Book', 10,
mapnik.Color('rgba(0,0,0,.8)') )
t.avoid_edges = True
t.halo_fill = mapnik.Color('rgba(255,255,255,.2)')
t.halo_radius = 2
r.symbols.append(t)
r.filter = feature_filter
s.rules.append(r)
m.remove_style('selected')
m.append_style('selected',s)
im = mapnik.Image(m.width,m.height)
mapnik.render(m, im)
file = "c:\\IVVSL\\Results\\IVirMAP.png"
print 'Rendering %s...' % file
im.save(file)
I'm guessing that it is redrawing the map at each iteration of the PosQuery
loop, and my previous labels are being obscured, but I don't see which command
is causing it. I've tried commenting out different lines to see how it affects
it, but it still isn't clear. Does anybody have any suggestions as to how to
modify this loop to append all of the symbols on the same map. It seems like
it should be an easy issue to resolve, but I've tried many permutations of this
code, and the result always ends up the same. ie. if i have a table with
Canada, Hong Kong, and the United States (in that order) the only country that
gets labeled is the United States. I'd appreciate any assistance that you can
provide to a mapnik noob. Thanks.
-Roger
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