def simplify(self):
"""
Reduce the number of vertices in a polygon layer.
* Delete vertex if the angle with its adjacents is near of the straight
angle for less than 'straight_thr' degrees in all its parents.
* Delete vertex if the distance to the segment formed by its parents is
less than 'cath_thr' meters.
"""
if log.app_level <= logging.DEBUG:
debshp = DebugWriter("debug_simplify.shp", self)
killed = 0
to_change = {}
# Clean non corners
(parents_per_vertex,
geometries) = self.get_parents_per_vertex_and_geometries()
pbar = self.get_progressbar(_("Simplify"), len(parents_per_vertex))
for wkt, parents in parents_per_vertex.items():
point = Point(wkt)
# Test if this vertex is a 'corner' in any of its parent polygons
for fid in parents:
geom = geometries[fid]
(angle, is_acute, is_corner,
cath) = point.get_corner_context(geom)
debmsg = "angle=%.1f, is_acute=%s, is_corner=%s, cath=%.4f" % (
angle,
is_acute,
is_corner,
cath,
)
if is_corner:
break
msg = "Keep"
if not is_corner:
killed += 1 # delete the vertex from all its parents.
for fid in frozenset(parents):
g = QgsGeometry(geometries[fid])
(__, ndx, __, __, __) = g.closestVertex(point)
(ndxa, ndxb) = g.adjacentVertices(ndx)
v = g.vertexAt(ndx)
va = g.vertexAt(ndxa)
vb = g.vertexAt(ndxb)
invalid_ring = v == va or v == vb or va == vb
g.deleteVertex(ndx)
msg = "Refused"
if Geometry.is_valid(g) and not invalid_ring:
parents.remove(fid)
geometries[fid] = g
to_change[fid] = g
msg = "Deleted"
if log.app_level <= logging.DEBUG:
debshp.add_point(point, msg + " " + debmsg)
if len(to_change) > BUFFER_SIZE:
self.writer.changeGeometryValues(to_change)
to_change = {}
pbar.update()
pbar.close()
if len(to_change) > 0:
self.writer.changeGeometryValues(to_change)
if killed > 0:
log.debug(_("Simplified %d vertices in the '%s' layer"), killed,
self.name())
report.values["vertex_simplify_" + self.name()] = killed
