app/django/contrib/gis/utils/wkt.py
author Pawel Solyga <Pawel.Solyga@gmail.com>
Mon, 01 Jun 2009 22:23:46 +0200
changeset 2376 feec28b50f1b
parent 323 ff1a9aa48cfd
permissions -rw-r--r--
Extend taggable-mixin to support different Tag models. Usage is pretty simple. Tag model is default in Taggable constructor but you can call it with different model like GHOPTaskType that inherits from Tag model. Both Taggable and Tag models have been updated and they don't use hardcoded Tag model anymore and instead use cls of class methods or self.__class__. In case of Taggable it's self.__tag_model.

"""
 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)])