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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.

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1 Answer 1

up vote 4 down vote accepted

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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Thanks for your answer. So to makes things clear: there is no ogr build-in function that does this? –  LarsVegas Mar 19 at 14:12
    
I don't think so –  radouxju Mar 19 at 14:16
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