Source code for TileCache.Layers.Mapnik

# BSD Licensed, Copyright (c) 2006-2010 TileCache Contributors

import sys

from TileCache.Layer import MetaLayer

class Mapnik(MetaLayer):
    
    config_properties = [
      {'name':'name', 'description': 'Name of Layer'}, 
      {'name':'mapfile', 'description': 'Location of Mapnik XML map description.'},
      {'name':'projection', 'description': 'Target map projection.'},
      {'name':'fonts', 'description': 'Comma-seperated list of fonts to add to the Mapik registered fonts list.'},
    ] + MetaLayer.config_properties 
    
    def __init__ (self, name, mapfile = None, projection = None, fonts = None, **kwargs):
        MetaLayer.__init__(self, name, **kwargs) 
        self.mapfile = mapfile
        self.mapnik  = None
        self.projection = projection
        if fonts:
            self.fonts = fonts.split(",")
        else:
            self.fonts = []
            
    def renderTile(self, tile):
        import mapnik
        
        if self.mapnik:
            m = self.mapnik
        else:
            if self.fonts:
                engine = mapnik.FontEngine.instance()
                for font in self.fonts:
                    engine.register_font(font)
            
            # Init it as 0,0
            m = mapnik.Map( 0, 0 )
            mapnik.load_map(m,self.mapfile)
             
            if self.projection:
                m.srs = self.projection
            
            # Restrict layer list, if requested
            if self.layers and self.layers != self.name:
                layers = self.layers.split(",")
                for layer_num in range(len(m.layers)-1, -1, -1):
                    l = m.layers[layer_num]
                    if l.name not in layers:
                        del m.layers[layer_num]
                        if self.debug:
                            print >>sys.stderr, "Removed layer %s loaded from %s, not in list: %s" % (l.name, self.mapfile, layers)
                        
            # this will insure that it gets cached in mod_python
            self.mapnik = m
        
        
        # Set the mapnik size to match the size of the current tile 
        m.width = tile.size()[0]
        m.height = tile.size()[1]
        
        bbox = tile.bounds()
        bbox = mapnik.Envelope(bbox[0], bbox[1], bbox[2], bbox[3])
        m.zoom_to_box(bbox)
                    
        im = mapnik.Image( *tile.size() )
        mapnik.render(m, im)
        if hasattr(im, 'tostring'):
            if self.paletted:
                data = im.tostring('png256')
            else:
                data = im.tostring(self.extension)
            tile.data = data
            return tile.data
        elif hasattr(mapnik, 'rawdata'):
            data = mapnik.rawdata(im)
            import PIL.Image, StringIO
            im = PIL.Image.fromstring('RGBA', tile.size(), data)
            buffer = StringIO.StringIO()
            if self.paletted:
                print >>sys.stderr, "Mapnik's 8-bit (png256) format not supported with PIL"
            im.save(buffer, self.extension)
            buffer.seek(0)
            tile.data = buffer.read()
            return tile.data 
        else:
            raise Exception("Something is wrong: your version of Mapnik can't create a string from an image.")