added .to_geo(centered=True)

quadkey/__init__.py

@@ -8,7 +8,7 @@ def __init__(self, key):
 		"""
 		A quadkey must be between 1 and 23 digits and can only contain digit[0-3]
 		"""
-		self.key = key 
+		self.key = key
 		self.level = len(key)
 
 	def children(self):
@@ -31,7 +31,7 @@ def is_ancestor(self, node):
 			Get the difference in level
 			If not, None
 		"""
-		if self.level <= node.level or self.key[:len(node.key)] != node.key: 
+		if self.level <= node.level or self.key[:len(node.key)] != node.key:
 			return None
 		return self.level - node.level
 
@@ -53,11 +53,11 @@ def area(self):
 	def to_tile(self):
 		return TileSystem.quadkey_to_tile(self.key)
 
-	def to_geo(self):
+	def to_geo(self, centered=False):
 		ret = TileSystem.quadkey_to_tile(self.key)
 		tile = ret[0]
 		lvl = ret[1]
-		pixel = TileSystem.tile_to_pixel(tile)
+		pixel = TileSystem.tile_to_pixel(tile, centered)
 		return TileSystem.pixel_to_geo(pixel, lvl)
 
 	def __eq__(self, other):
@@ -84,7 +84,7 @@ def from_geo(geo, level):
 		pixel = TileSystem.geo_to_pixel(geo, level)
 		tile = TileSystem.pixel_to_tile(pixel)
 		key = TileSystem.tile_to_quadkey(tile, level)
-		return QuadKey(key) 
+		return QuadKey(key)
 
 	@staticmethod
 	def from_tile(tile, level):

quadkey/tile_system.py

@@ -82,9 +82,13 @@ def pixel_to_tile(pixel):
 		return pixel[0] / 256, pixel[1] / 256
 
 	@staticmethod
-	def tile_to_pixel(tile):
+	def tile_to_pixel(tile, centered=False):
 		"""Transform tile to pixel coordinates"""
-		return tile[0] * 256, tile[1] * 256
+		pixel = [tile[0] * 256, tile[1] * 256]
+		if centered:
+			#should clip on max map size
+			pixel = [pix + 128 for pix in pixel]
+		return pixel[0], pixel[1]
 
 	@staticmethod
 	@precondition(lambda tile, lvl: valid_level(lvl))

setup.py

@@ -3,7 +3,7 @@
 from setuptools import setup
 
 setup(name="quadkey",
-		version="0.0.3",
+		version="0.0.4",
 		description="Python Implementation for Geospatial Quadkeys",
 		author="Buck Heroux",
 		url="https://github.com/buckheroux/QuadKey",