Hello everyone: I'm newbie with mapnik, when I use the demo easymapnik example I confronted some problems, most of time I get a blank map. I know it's the projection problem and tried many ways others used, and the result is negative. So I made a simple python file to render map and the result is the same, a blank map.
My python file. #!/usr/bin/python import mapnik mapnikfile = "test.xml" proj = "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgri...@null +no_defs +over" m = mapnik.Map(500,500) ll=(-1.45,50.9,51,1.35) mapnik.load_map(m,mapnikfile) m.srs = proj prj = mapnik.Projection(proj) bbox = prj.forward(mapnik.Envelope(ll[0],ll[1],ll[2],ll[3])) print bbox #m.zoom_all() #when I use zoom_all() instead of zoom_to_box(bbox), I got the right map m.zoom_to_box(bbox) print m.envelope() m.layers[0].srs=proj # I set the layer's srs and don't know how to convert the envelope to merc form print "map layers" print m.layers[0].srs print m.layers[0].envelope() mapnik.render_to_file(m,"my.png") ~ I used the test.xml and test2.osm in the http://trac.mapnik.org/browser/trunk/plugins/input/osm?rev=919 After check some properties , the layer's srs is "+proj=latlong +datum=WGS84" and the map's srs is "+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgri...@null +no_defs +over".It seems like the reason why I just got blank map. I thought I should let the layer's coordinate as map's. So I try to set the layer's srs to the same as map's, but I don't find how to convert layer's envelope to the merc form. Can anyone tell me how to convert the layer's envelope or point my mistake? Thank you! With nik2img.py, the result is good. -- Matrix Bai http://matrix.3p-blog.com
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