def _mbr_orientation(mbr: QgsPolygon):
'''
Compute the orientation of a minimum bounding rectangle (QgsPolygon)
(in degrees) comparatively to the cartographic East (axis X).
Its value is between 0 and 180 degrees.
'''
# , except if the MBR is geometrically
# null or empty. In that last case, the value -2.0 is returned.
# if mbr.isNull() or mbr.isEmpty():
# return -2.0
# geom = mbr.geometry()
mbr_vertices = _geometry_vertices(mbr, 2)
v0 = QgsPoint(mbr_vertices[0].x(), mbr_vertices[0].y())
v1 = QgsPoint(mbr_vertices[1].x(), mbr_vertices[1].y())
v2 = QgsPoint(mbr_vertices[2].x(), mbr_vertices[2].y())
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 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
