Hi Chris, Mapnik won't re-project raster on fly, yet. This is something I'd like to implement but for the time being you must re-project your geotiff to master map projection (900913) using external tools like gdal.
Cheers, Artem 2009/7/28 Chris Emberson <[email protected]>: > Dear Mapnik users, > > I am suffering from the 'empty tile' syndrome - attempting to tile a Geotiff > using generate_tiles.py which creates transparent tiles. > I have implemented the suggestions on similar posts, but still to no avail.. > > Can you help? > > Thanks, > Chris > > code is as follows..... > > #!/usr/bin/python > from math import pi,cos,sin,log,exp,atan > from subprocess import call > import sys, os > > DEG_TO_RAD = pi/180 > RAD_TO_DEG = 180/pi > > def minmax (a,b,c): > a = max(a,b) > a = min(a,c) > return a > > class GoogleProjection: > def __init__(self,levels=18): > self.Bc = [] > self.Cc = [] > self.zc = [] > self.Ac = [] > c = 256 > for d in range(0,levels): > e = c/2; > self.Bc.append(c/360.0) > self.Cc.append(c/(2 * pi)) > self.zc.append((e,e)) > self.Ac.append(c) > c *= 2 > > def fromLLtoPixel(self,ll,zoom): > d = self.zc[zoom] > e = round(d[0] + ll[0] * self.Bc[zoom]) > f = minmax(sin(DEG_TO_RAD * ll[1]),-0.9999,0.9999) > g = round(d[1] + 0.5*log((1+f)/(1-f))*-self.Cc[zoom]) > return (e,g) > > def fromPixelToLL(self,px,zoom): > e = self.zc[zoom] > f = (px[0] - e[0])/self.Bc[zoom] > g = (px[1] - e[1])/-self.Cc[zoom] > h = RAD_TO_DEG * ( 2 * atan(exp(g)) - 0.5 * pi) > return (f,h) > > from mapnik import * > > def render_tiles(bbox, mapfile, tile_dir, minZoom=1,maxZoom=18, > name="unknown"): > print "render_tiles(",bbox, mapfile, tile_dir, minZoom,maxZoom, name,")" > > if not os.path.isdir(tile_dir): > os.mkdir(tile_dir) > > gprj = GoogleProjection(maxZoom+1) > m = Map(2 * 256,2 * 256) > load_map(m,mapfile) > > prj = Projection("+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") > > ll0 = (bbox[0],bbox[3]) > ll1 = (bbox[2],bbox[1]) > > for z in range(minZoom,maxZoom + 1): > px0 = gprj.fromLLtoPixel(ll0,z) > px1 = gprj.fromLLtoPixel(ll1,z) > > # check if we have directories in place > zoom = "%s" % z > if not os.path.isdir(tile_dir + 'Z' + zoom): > os.mkdir(tile_dir + 'Z' + zoom) > for x in range(int(px0[0]/256.0),int(px1[0]/256.0)+1): > # check if we have directories in place > str_x = "%s" % x > for y in range(int(px0[1]/256.0),int(px1[1]/256.0)+1): > p0 = gprj.fromPixelToLL((x * 256.0, (y+1) * 256.0),z) > p1 = gprj.fromPixelToLL(((x+1) * 256.0, y * 256.0),z) > > # render a new tile and store it on filesystem > c0 = prj.forward(Coord(p0[0],p0[1])) > c1 = prj.forward(Coord(p1[0],p1[1])) > > bbox = Envelope(c0.x,c0.y,c1.x,c1.y) > bbox.width(bbox.width() * 2) > bbox.height(bbox.height() * 2) > m.zoom_to_box(bbox) > > str_y = "%s" % y > > if not os.path.isdir(tile_dir + 'Z' + zoom + '/' + str_y): > os.mkdir(tile_dir + 'Z' + zoom + '/' + str_y) > tile_uri = tile_dir + 'Z' + zoom + '/' + str_y + '/' + str_x > + '.png' > exists= "" > if os.path.isfile(tile_uri): > exists= "exists" > else: > render_to_file(m, tile_uri) > im = Image(512, 512) > render(m, im) > view = im.view(128,128,256,256) # x,y,width,height > view.save(tile_uri,'png') > # command = "convert -colors 255 %s %s" % > (tile_uri,tile_uri) > # call(command, shell=True) > > bytes=os.stat(tile_uri)[6] > empty= '' > if bytes == 334: > empty = " Empty Tile " > > print name,"[",minZoom,"-",maxZoom,"]: " > ,z,x,y,"p:",p0,p1,exists, empty > > if __name__ == "__main__": > home = os.environ['HOME'] > mapfile = '/home/chrise/rasters/rasters2.xml' > tile_dir = '/home/chrise/rasters/tiles/' > > > #------------------------------------------------------------------------- > # > # Change the following for different bounding boxes and zoom levels > # > # Start with an overview > # World > > minZoom = 8 # 8 & 9 don't show names > maxZoom = 12 > # Original > #bbox = (-4.19104,50.55263,-3.74899,51.77649) > # Full area > #bbox = (-5.39104,50.55263,-3.74899,52.37649) > # Tiny > #bbox = (-3.97915,51.61631,-3.95435,51.62137) > # [ (51.61352,-3.98052), (51.6289,-3.93092) ] > #bbox = (-3.98052,51.61352,-3.93092,51.6289) > # London > bbox = (-0.5527,51.22825,0.33372,51.70009) > > render_tiles(bbox, mapfile, tile_dir, minZoom, maxZoom, "dem") > > > > > rasters2.xml............ > > <?xml version="1.0" encoding="utf-8"?> > <!DOCTYPE Map> > > <Map srs="+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"> > > <Style name="My Style"> > <Rule> > <RasterSymbolizer> > <CssParameter name="opacity">0.8</CssParameter> > <!-- <CssParameter name="scaling">fast</CssParameter>--> > <!-- <CssParameter name="mode">multiply</CssParameter>--> > </RasterSymbolizer> > </Rule> > </Style> > > > <Layer name="dem" status="on" > > <StyleName>raster</StyleName> > <Datasource> > <Parameter name="type">raster</Parameter> > <Parameter > name="file">/home/chrise/rasters/q5_proc_prj.tiff</Parameter> > <Parameter name="lox">-58366.462</Parameter> > <Parameter name="loy">6746403.661</Parameter> > <Parameter name="hix">38553.750</Parameter> > <Parameter name="hiy">6670183.296</Parameter> > </Datasource> > </Layer> > > </Map> > > > > > > ________________________________ > Celebrate a decade of Messenger with free winks, emoticons, display pics, > and more. Get Them Now > _______________________________________________ > Mapnik-users mailing list > [email protected] > https://lists.berlios.de/mailman/listinfo/mapnik-users > > _______________________________________________ Mapnik-users mailing list [email protected] https://lists.berlios.de/mailman/listinfo/mapnik-users
