gis: Added the precision_wkt utility; add_postgis_srs may now take WKT/PROJ.4 strings and integer SRIDs.

git-svn-id: http://code.djangoproject.com/svn/django/branches/gis@7547 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/gis/utils/__init__.py

@@ -21,3 +21,5 @@ except:
     HAS_GEOIP = False
 
 from django.contrib.gis.utils.srs import add_postgis_srs
+from django.contrib.gis.utils.wkt import precision_wkt
+

django/contrib/gis/utils/srs.py

@@ -1,3 +1,5 @@
+from django.contrib.gis.gdal import SpatialReference
+
 def add_postgis_srs(srs):
     """
     This function takes a GDAL SpatialReference system and adds its
@@ -14,6 +16,9 @@ def add_postgis_srs(srs):
     """
     from django.contrib.gis.models import SpatialRefSys
 
+    if not isinstance(srs, SpatialReference):
+        srs = SpatialReference(srs)
+
     if srs.srid is None:
         raise Exception('Spatial reference requires an SRID to be compatible with PostGIS.')
    

django/contrib/gis/utils/wkt.py

@@ -0,0 +1,55 @@
+"""
+ Utilities for manipulating Geometry WKT.
+"""
+
+def precision_wkt(geom, prec):
+    """
+    Returns WKT text of the geometry according to the given precision (an 
+    integer or a string).  If the precision is an integer, then the decimal
+    places of coordinates WKT will be truncated to that number:
+
+     >>> pnt = Point(5, 23)
+     >>> pnt.wkt
+     'POINT (5.0000000000000000 23.0000000000000000)'
+     >>> precision(geom, 1)
+     'POINT (5.0 23.0)'
+
+    If the precision is a string, it must be valid Python format string 
+    (e.g., '%20.7f') -- thus, you should know what you're doing.
+    """
+    if isinstance(prec, int):
+        num_fmt = '%%.%df' % prec
+    elif isinstance(prec, basestring):
+        num_fmt = prec
+    else:
+        raise TypeError
+
+    # TODO: Support 3D geometries.
+    coord_fmt = ' '.join([num_fmt, num_fmt])
+
+    def formatted_coords(coords):
+        return ','.join([coord_fmt % c[:2] for c in coords])
+
+    def formatted_poly(poly):
+        return ','.join(['(%s)' % formatted_coords(r) for r in poly])
+
+    def formatted_geom(g):
+        gtype = str(g.geom_type).upper()
+        yield '%s(' % gtype
+        if gtype == 'POINT':
+            yield formatted_coords((g.coords,))
+        elif gtype in ('LINESTRING', 'LINEARRING'):
+            yield formatted_coords(g.coords)
+        elif gtype in ('POLYGON', 'MULTILINESTRING'):
+            yield formatted_poly(g)
+        elif gtype == 'MULTIPOINT':
+            yield formatted_coords(g.coords)
+        elif gtype == 'MULTIPOLYGON':
+            yield ','.join(['(%s)' % formatted_poly(p) for p in g])
+        elif gtype == 'GEOMETRYCOLLECTION':
+            yield ','.join([''.join([wkt for wkt in formatted_geom(child)]) for child in g])
+        else:
+            raise TypeError
+        yield ')'
+
+    return ''.join([wkt for wkt in formatted_geom(geom)])