OGR Python – Equivalent Function to Shapely’s Envelope

extentsogrpythonshapely

I wrote a very simple python function that gives me the envelope/bounding box/…based on two coordinate pairs (ower left and upper right corner):

# ...
def get_bounding_box(self, ll_corner, ur_corner):
    try:
        from shapely.geometry import MultiPoint
        mp_env = MultiPoint([ll_corner, ur_corner]).envelope
        return ogr.CreateGeometryFromWkt( mp_env.to_wkt() )

print mp_env
POLYGON ((4.8439699999999997 52.3661099999999990, 4.8469199999999999 52.3661099999999990, 4.8469199999999999 52.3706000000000031, 4.8439699999999997 52.3706000000000031, 4.8439699999999997 52.3661099999999990))

As you can see I'm returning an ogr geometry which I use, for instance, in this manner:

bbox = geo.get_bounding_box(lowerleft,upper_right) 
...
p=ogr.Geometry(ogr.wkbPoint)
p.AddPoint(x,y)
if p.Within(bbox):
    ....

Isn't there an equivalent function to shapely's envelope in ogr? Both .ConvexHull() and GetEnvelope() return only the two corner coordinate pairs.

Best Answer

The Ogr function GetEnvelope() returns "a tuple (minX, maxX, minY, maxY)" (from here), but what you want (from what I can understand) is a Polygon describing the envelope/bbox?

This is actually rather simple, as the tuple (minX, maxX, minY, maxY) is all you need to create a Polygon.

Just create a Polygon based these, like so:

from osgeo import ogr

def my_envelope(geom):
   (minX, maxX, minY, maxY) = geom.GetEnvelope()

    # Create ring
    ring = ogr.Geometry(ogr.wkbLinearRing)
    ring.AddPoint(minX, minY)
    ring.AddPoint(maxX, minY)
    ring.AddPoint(maxX, maxY)
    ring.AddPoint(minX, maxY)
    ring.AddPoint(minX, minY)

    # Create polygon
    poly_envelope = ogr.Geometry(ogr.wkbPolygon)
    poly_envelope.AddGeometry(ring)
    return poly_envelope
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