Merge pull request #7 from JoeGermuska/grid

add grid rendering

invar/renderer.py

@@ -9,6 +9,9 @@
 import constants
 import projections
 
+import json
+from os.path import splitext
+
 class Renderer(multiprocessing.Process):
     """
     A Mapnik renderer process.
@@ -69,6 +72,12 @@ class TileRenderer(Renderer):
     """
     Renderer for tiles. 
     """
+    def __init__(self, tile_queues, config, width=constants.DEFAULT_WIDTH, height=constants.DEFAULT_HEIGHT, filetype=constants.DEFAULT_FILE_TYPE, buffer_size=None, skip_existing=False, **kwargs):
+        super(TileRenderer, self).__init__(tile_queues, config, width, height, filetype, buffer_size, skip_existing)
+        self.grid = kwargs.get('grid',False)
+        self.key =  kwargs.get('key',None)
+        self.fields =  kwargs.get('fields',None)
+
     def render(self, filename, tile_x, tile_y, zoom):
         """
         Render a single tile to a given filename.
@@ -99,6 +108,30 @@ def render(self, filename, tile_x, tile_y, zoom):
         image = mapnik.Image(self.width, self.height)
         mapnik.render(self.mapnik_map, image)
         image.save(filename, self.filetype)
+
+        if self.grid:
+            if self.key:
+                grid = mapnik.Grid(self.width, self.height)
+            else:
+                grid = mapnik.Grid(self.width, self.height, key=self.key)
+
+            fields = []
+            if self.fields:
+                fields.extend(self.fields)
+
+            mapnik.render_layer(self.mapnik_map,grid,layer=0,fields=fields)
+            # then encode the grid array as utf, resample to 1/4 the size, and dump features
+            # this comes from https://github.com/springmeyer/gridsforkids/blob/master/generate_tiles.py 
+            # with little consideration
+            grid_utf = grid.encode('utf', resolution=4, features=True)
+
+            # client code uses jsonp, so fake by wrapping in grid() callback
+            base, ext = splitext(filename)
+            grid_filename = "%s.grid.json" % base
+            print 'Rendering %s' % (grid_filename)
+            open(grid_filename,'wb').write('grid(' + json.dumps(grid_utf) + ')')
+
+
 
 class FrameRenderer(Renderer):
     """

ivtile

@@ -23,7 +23,11 @@ class IVTile(invar.InvarUtility):
         self.argparser.add_argument('lon_2', type=float, help="Most eastern longitude")
         self.argparser.add_argument('min_zoom', help="Minimum zoom level to render", type=int, default=DEFAULT_MIN_ZOOM)
         self.argparser.add_argument('max_zoom', help="Maximum zoom level to render", type=int, default=DEFAULT_MAX_ZOOM)
-
+
+        self.argparser.add_argument('-g', '--grid', action="store_true", help="Force grid JSON to be rendered alongside each tile. If -k or -f options are provided, this is inferred and need not be specified.")
+        self.argparser.add_argument('-k', '--key', help="For grid rendering, the column in the associated dataset which is a unique ID for a feature. If not specified, will use mapnik default ('__id__')")
+        self.argparser.add_argument('-f', '--fields', help="For grid rendering, a comma separated list of fields associated with each feature which will be included in grid JSON.")
+
     def main(self):
         if not os.path.isdir(self.args.output_dir):
              os.mkdir(self.args.output_dir)
@@ -87,9 +91,14 @@ class IVTile(invar.InvarUtility):
         print 'Using %i processes to render %i tiles' % (self.args.process_count, tile_count)
 
         processes = []
-
+        try:
+            fields = self.args.fields.split(",")
+        except:
+            fields = None
+
         for i in range(self.args.process_count):
-            renderer = invar.TileRenderer(tile_queues, self.args.config, self.args.width, self.args.height, buffer_size=self.args.buffer, skip_existing=self.args.skip_existing)
+            grid = (self.args.grid or self.args.fields or self.args.key)
+            renderer = invar.TileRenderer(tile_queues, self.args.config, self.args.width, self.args.height, buffer_size=self.args.buffer, skip_existing=self.args.skip_existing, grid=grid, key=self.args.key, fields=fields)
             renderer.start()
 
             processes.append(renderer)