#10380: gdal Envelope should allow min_x == max_x and/or min_y == max_y
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Reporter: psmith | Owner: nobody
Status: new | Milestone:
Component: GIS | Version: 1.0
Keywords: envelope extent gdal | Stage: Unreviewed
Has_patch: 0 |
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When initializing a new {{{django.contrib.gis.gdal.Envelope}}} object, an
{{{OGRException}}} is raised if the {{{min_x}}} value is less than or
equal to {{{max_x}}}, and if the {{{min_y}}} value is less than or equal
to {{{max_y}}}. It would be better if the exception was raised on in the
case that {{{min_x}}} was greater than {{{max_x}}} and/or if {{{min_y}}}
greater than {{{max_y}}}.
The reason that it is often useful to create an {{{Envelope}}} from a
point initially, say from the extent of a
{{{django.contrib.gis.geos.Point}}} object, where the {{{min_x}}} and
{{{min_y}}} will equal the {{{max_x}}} and {{{max_y}}}, respectively. For
example, to find the extent of a set or list of points, it is convenient
to iterate over the collection, creating the Envelope initially with the
first point from the iteration, then expanding it with each successive
point. (Perhaps using the {{{expand_to_include}}} method proposed in
#10368.)
Example:
{{{
>>> from django.contrib.gis.geos import Point
>>> from django.contrib.gis.gdal import Envelope
>>> env = None
>>> for pt in [Point(5, 10), Point(-1, 3), Point(9, -2)]:
... if env is None:
... env = Envelope(pt.extent)
... else:
... env.expand_to_include(pt.extent)
>>> env.tuple
(-1, -2, 9, 10)
}}}
Making this change should have no impact on the semantics of the
{{{Envelope}}} class: indeed, the {{{OGREnvelope}}} class in
{{{ogr_core.h}}} from which it is derived does not enforce or check for
the ordering of the min and max values.
--
Ticket URL: <http://code.djangoproject.com/ticket/10380>
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