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Diffstat (limited to 'lib/python2.7/site-packages/django/contrib/gis/gdal/envelope.py')
| -rw-r--r-- | lib/python2.7/site-packages/django/contrib/gis/gdal/envelope.py | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/lib/python2.7/site-packages/django/contrib/gis/gdal/envelope.py b/lib/python2.7/site-packages/django/contrib/gis/gdal/envelope.py new file mode 100644 index 0000000..f145526 --- /dev/null +++ b/lib/python2.7/site-packages/django/contrib/gis/gdal/envelope.py @@ -0,0 +1,175 @@ +""" + The GDAL/OGR library uses an Envelope structure to hold the bounding + box information for a geometry. The envelope (bounding box) contains + two pairs of coordinates, one for the lower left coordinate and one + for the upper right coordinate: + + +----------o Upper right; (max_x, max_y) + | | + | | + | | + Lower left (min_x, min_y) o----------+ +""" +from ctypes import Structure, c_double +from django.contrib.gis.gdal.error import OGRException + +# The OGR definition of an Envelope is a C structure containing four doubles. +# See the 'ogr_core.h' source file for more information: +# http://www.gdal.org/ogr/ogr__core_8h-source.html +class OGREnvelope(Structure): + "Represents the OGREnvelope C Structure." + _fields_ = [("MinX", c_double), + ("MaxX", c_double), + ("MinY", c_double), + ("MaxY", c_double), + ] + +class Envelope(object): + """ + The Envelope object is a C structure that contains the minimum and + maximum X, Y coordinates for a rectangle bounding box. The naming + of the variables is compatible with the OGR Envelope structure. + """ + + def __init__(self, *args): + """ + The initialization function may take an OGREnvelope structure, 4-element + tuple or list, or 4 individual arguments. + """ + + if len(args) == 1: + if isinstance(args[0], OGREnvelope): + # OGREnvelope (a ctypes Structure) was passed in. + self._envelope = args[0] + elif isinstance(args[0], (tuple, list)): + # A tuple was passed in. + if len(args[0]) != 4: + raise OGRException('Incorrect number of tuple elements (%d).' % len(args[0])) + else: + self._from_sequence(args[0]) + else: + raise TypeError('Incorrect type of argument: %s' % str(type(args[0]))) + elif len(args) == 4: + # Individual parameters passed in. + # Thanks to ww for the help + self._from_sequence([float(a) for a in args]) + else: + raise OGRException('Incorrect number (%d) of arguments.' % len(args)) + + # Checking the x,y coordinates + if self.min_x > self.max_x: + raise OGRException('Envelope minimum X > maximum X.') + if self.min_y > self.max_y: + raise OGRException('Envelope minimum Y > maximum Y.') + + def __eq__(self, other): + """ + Returns True if the envelopes are equivalent; can compare against + other Envelopes and 4-tuples. + """ + if isinstance(other, Envelope): + return (self.min_x == other.min_x) and (self.min_y == other.min_y) and \ + (self.max_x == other.max_x) and (self.max_y == other.max_y) + elif isinstance(other, tuple) and len(other) == 4: + return (self.min_x == other[0]) and (self.min_y == other[1]) and \ + (self.max_x == other[2]) and (self.max_y == other[3]) + else: + raise OGRException('Equivalence testing only works with other Envelopes.') + + def __str__(self): + "Returns a string representation of the tuple." + return str(self.tuple) + + def _from_sequence(self, seq): + "Initializes the C OGR Envelope structure from the given sequence." + self._envelope = OGREnvelope() + self._envelope.MinX = seq[0] + self._envelope.MinY = seq[1] + self._envelope.MaxX = seq[2] + self._envelope.MaxY = seq[3] + + def expand_to_include(self, *args): + """ + Modifies the envelope to expand to include the boundaries of + the passed-in 2-tuple (a point), 4-tuple (an extent) or + envelope. + """ + # We provide a number of different signatures for this method, + # and the logic here is all about converting them into a + # 4-tuple single parameter which does the actual work of + # expanding the envelope. + if len(args) == 1: + if isinstance(args[0], Envelope): + return self.expand_to_include(args[0].tuple) + elif hasattr(args[0], 'x') and hasattr(args[0], 'y'): + return self.expand_to_include(args[0].x, args[0].y, args[0].x, args[0].y) + elif isinstance(args[0], (tuple, list)): + # A tuple was passed in. + if len(args[0]) == 2: + return self.expand_to_include((args[0][0], args[0][1], args[0][0], args[0][1])) + elif len(args[0]) == 4: + (minx, miny, maxx, maxy) = args[0] + if minx < self._envelope.MinX: + self._envelope.MinX = minx + if miny < self._envelope.MinY: + self._envelope.MinY = miny + if maxx > self._envelope.MaxX: + self._envelope.MaxX = maxx + if maxy > self._envelope.MaxY: + self._envelope.MaxY = maxy + else: + raise OGRException('Incorrect number of tuple elements (%d).' % len(args[0])) + else: + raise TypeError('Incorrect type of argument: %s' % str(type(args[0]))) + elif len(args) == 2: + # An x and an y parameter were passed in + return self.expand_to_include((args[0], args[1], args[0], args[1])) + elif len(args) == 4: + # Individual parameters passed in. + return self.expand_to_include(args) + else: + raise OGRException('Incorrect number (%d) of arguments.' % len(args[0])) + + @property + def min_x(self): + "Returns the value of the minimum X coordinate." + return self._envelope.MinX + + @property + def min_y(self): + "Returns the value of the minimum Y coordinate." + return self._envelope.MinY + + @property + def max_x(self): + "Returns the value of the maximum X coordinate." + return self._envelope.MaxX + + @property + def max_y(self): + "Returns the value of the maximum Y coordinate." + return self._envelope.MaxY + + @property + def ur(self): + "Returns the upper-right coordinate." + return (self.max_x, self.max_y) + + @property + def ll(self): + "Returns the lower-left coordinate." + return (self.min_x, self.min_y) + + @property + def tuple(self): + "Returns a tuple representing the envelope." + return (self.min_x, self.min_y, self.max_x, self.max_y) + + @property + def wkt(self): + "Returns WKT representing a Polygon for this envelope." + # TODO: Fix significant figures. + return 'POLYGON((%s %s,%s %s,%s %s,%s %s,%s %s))' % \ + (self.min_x, self.min_y, self.min_x, self.max_y, + self.max_x, self.max_y, self.max_x, self.min_y, + self.min_x, self.min_y) |