def polygon_orientation(polygon: QgsPolygon):
'''
Compute the orientation of a polygon (QgsPolygon) (in degrees)
comparatively to the cartographic East (axis X).
The orientation is based on the orientation of the associated minimum
bounding rectangle. Its value is between 0 and 180 degrees, except if
the MBR can not be defined. In that last case, the value -2.0 is returned.
'''
# orientedMinimumBoundingBox(self) → Tuple[QgsGeometry, float, float, float, float]
# angle (clockwise in degrees from North)
(mbr, area, angle, width, height) = polygon.orientedMinimumBoundingBox()
if mbr.isNull() or mbr.isEmpty():
return -2.0
# geom = mbr.geometry()
v0 = QgsPoint(mbr[0])
v1 = QgsPoint(mbr[1])
v2 = QgsPoint(mbr[2])
length = v0.distanceSquared(v1.x(), v1.y())
length2 = v1.distanceSquared(v2.x(), v2.y())
if length > length2:
angle = math.atan2(v0.y() - v1.y(), v0.x() - v1.x())
else:
angle = math.atan2(v1.y() - v2.y(), v1.x() - v2.x())
if angle < 0:
angle += math.pi
return angle * 180.0 / math.pi
def is_rectangle(polygon: QgsPolygon, sd_convex_hull_threshold: float,
sd_mbr_threshold: float, distance_area: QgsDistanceArea):
'''
Compute if a {@link Polygon} has a rectangular shape or not, based on the comparison
with two shapes: the shape of the minimum bounding rectangle of the {@link Polygon},
and the shape of the convex hull associated to the {@link Polygon}. This comparison
is computed thanks to two thresholds (threshold of maximums), one for each associated
shape. If the shape is rectangular, the orientation (in degrees) based on the is returned;
otherwise, the value of -1.0 is returned. Finally, if the returned value equals -2.0,
it means that the MBR can not be computed.
@param polygon polygon to process
@param sd_convex_hull_threshold maximum threshold for surface distance between the polygon and its convex hull
@param sd_mbr_threshold maximum threshold for surface distance between the polygon and its associated minimum bounding rectangle
@return the orientation in degrees of the polygon, based on the orientation of the associated minimum bounding rectangle,
-1.0 if the polygon shape is not defined as a rectangle, and -2.0 if the convex hull or MBR can not be computed
'''
convex_hull = polygon.convexHull()
if convex_hull.isNull() or convex_hull.isEmpty():
return -2.0
# orientedMinimumBoundingBox(self) → Tuple[QgsGeometry, float, float, float, float]
# angle (clockwise in degrees from North)
(mbr, area, angle, width, height) = polygon.orientedMinimumBoundingBox()
if mbr.isNull() or mbr.isEmpty():
return -2.0
sd_convex_hull = surface_distance(polygon, convex_hull, distance_area)
sd_mbr = surface_distance(polygon, mbr, distance_area)
if sd_convex_hull <= sd_convex_hull_threshold and sd_mbr <= sd_mbr_threshold:
return _mbr_orientation(mbr)
return -1.0
