Thanks Artem & Dane for your answers.
I'm giving generate_tiles.py a try.
I have commented lines 97 and 98 to avoid error messages, and executed
the main method:
------
mapfile = "C:/shapefiles/E.xml"
tile_dir = "C:/shapefiles/tiles"
bbox = (-7.4886349714,0.000345541930004,-7.48862510461,0.000366144026643)
render_tiles(bbox, mapfile, tile_dir, 4, 14, "E");
------
I've changed some code in order to have the tiles generated in
tiles/{Z}/{X}/{Y}.png insted of tiles{Z}/{X}/{Y}.png, according to de
format described in http://wiki.openstreetmap.org/wiki/Google_Maps_Example.
But anyway, only blank tiles are generated. One per folder. I thing the
bounding box is correct, it has been obtained through Layer.envelope()
method.
I have tried changing line 54 to my source projection
prj = Projection("+proj=latlong +datum=WGS84")
Although this should be de target projection, not the source one. Isn't it?
Am I missing something?
Thanks in advance.
--
Félix.
Artem Pavlenko escribió:
> Hi Félix,
>
> I had a quick look - 12567 x 33784 is quite big for an image but it
> should work with something like > 2GB of RAM. How much memory
> available to Python is OS specific. it might be possible to tweak not
> sure.
>
> I'm just thinking, why don't you use Mapnik to generate actual tiles.
> This way you won't have memory issues, also, re-sampling is
> sub-optimal when it comes to image quality.
>
> Here is link to very simple Python script you can try as a starting point:
> http://trac.openstreetmap.org/browser/applications/rendering/mapnik/generate_tiles.py
>
> You can just replace load_map(m,..) with your script, comment out line 97:
> # command = "convert -colors 255 %s %s" % (tile_uri,tile_uri)
> and change extent/projections.
>
> re: disabling anti-aliasing - the short answer is no. But you can work
> around 'border stitching' problem. First try adding LineSymbolizer to
> dilate polygons slightly. In the past I had solved this issue by
> implementing specialized 'compositing' renderer. I can try to dig some
> code if you're interested. This would be a great feature to have, but
> probably for 1.0.0.
>
>
> HTH,
>
> Best
> Artem
>
>
>> Hello,
>>
>> I'll try to describe my use case:
>>
>> We have some shapefiles wich we want to, as the final result, show on Google
>> Maps. These shapefiles are made of thousands of polygons, each being of 250
>> x 250 meters. These polygons have an integer feature associated, lets say
>> from 0 to 200. If the feature is below "50", the polygon must be rendered in
>> red. If betweeen "50 and 150", in yellow, and if above "150" in green.
>>
>> Our maximum visualization zoom level in Google Maps is 14, which gives a
>> resolution of ~ 7.4 m/px at the location of interest. (each polygon is then
>> ~ 34 px). The shapefile width is 93000 m and 250000 m height. With these
>> data, we believe we need to render the shapefile to a file (PNG) of 12567 x
>> 33784 px in size to keep the accuracy of the original shapefile.
>>
>> The code to render the png is:
>>
>> from mapnik import *
>>
>> m = Map(12567,33784,"+proj=latlong +datum=WGS84")
>> s = Style()
>>
>> a_rule=Rule()
>> a_rule.filter = Filter('[Value] > -87 and [Value] <= -78')
>> a_rule.symbols.append(PolygonSymbolizer(Color('#FF0000')))
>>
>> b_rule=Rule()
>> b_rule.filter = Filter('[Value] > -78 and [Value] <= -72')
>> b_rule.symbols.append(PolygonSymbolizer(Color('#FFFF00')))
>>
>> c_rule=Rule()
>> c_rule.filter = Filter('[Value] > -72')
>> c_rule.symbols.append(PolygonSymbolizer(Color('#00FF00')))
>>
>> s.rules.append(a_rule)
>> s.rules.append(b_rule)
>> s.rules.append(c_rule)
>>
>> m.append_style('My Style',s)
>> lyr = Layer('E')
>> lyr.datasource = Shapefile(file='C:/shapefiles/E')
>> lyr.styles.append('My Style')
>> m.layers.append(lyr)
>> m.zoom_to_box(lyr.envelope())
>> render_to_file(m,'C:/shapefiles/E.png', 'png')
>>
>> With that file size (12567,33784), we get a memory error. Is it possible to
>> increase the memory heap used by python in order to generate this file?
>>
>> If we reduce the file size (e.g. 8378, 22523), the file is rendered but due
>> to some antialiasing effect the borders of the polygons are blurred. We
>> attach a picture in which you can see this effect and another showing how we
>> would like to see it, as shown in Mapinfo loading directly the shape file
>> and with a thematic map.
>>
>> Is it possible to disable antialiasing using mapnik?
>>
>> Once we have the file generated, we want to generate tiles for Google Maps
>> from it either using gdal2tiles or tilecache + mapnik. In the first case, we
>> need the png file to be georreferenced. Is it possible from mapnik to
>> generate a world file for the png according to the extents and bound of the
>> source shapefile?
>>
>> We haven't explored yet the tilecache + mapnik approach. gdal2tiles provides
>> an option to resample the source file in order to generate missing pixels
>> for the desired zoom level, so we believe we can provide a tinier source
>> file which we can generate with mapnik from the shapefile, and then resample
>> to the desired zoom level without loosing accuracy. Is it possible to make
>> something similar with mapnik + tilecache?
>>
>> Thanks in advance.
>>
>> --
>> Félix
>>
>>
>> _______________________________________________
>> Mapnik-users mailing list
>> [email protected]
>> https://lists.berlios.de/mailman/listinfo/mapnik-users
>>
>>
>>
>
>
> ---------------------------------------------------------------------------------------------------
> Texto añadido por Panda Security for Desktops:
>
> Este mensaje NO ha sido clasificado como SPAM. Si se trata de un mensaje de
> correo no solicitado (SPAM), haz clic en el siguiente vínculo para
> reclasificarlo:
> http://localhost:6083/Panda?ID=pav_2126&SPAM=true&path=C:\Documents%20and%20Settings\fepe\Local%20Settings\Application%20Data\Panda%20Software\AntiSpam
> ---------------------------------------------------------------------------------------------------
>
>
>
_______________________________________________
Mapnik-users mailing list
[email protected]
https://lists.berlios.de/mailman/listinfo/mapnik-users
