inkstitch/lib/utils/geometry.py

# Authors: see git history
#
# Copyright (c) 2010 Authors
# Licensed under the GNU GPL version 3.0 or later.  See the file LICENSE for details.

import math

from shapely.geometry import LineString, LinearRing, MultiLineString, Polygon, MultiPolygon, MultiPoint, GeometryCollection
from shapely.geometry import Point as ShapelyPoint


def cut(line, distance, normalized=False):
    """ Cuts a LineString in two at a distance from its starting point.

    This is an example in the Shapely documentation.
    """
    if normalized:
        distance *= line.length

    if distance <= 0.0:
        return [None, line]
    elif distance >= line.length:
        return [line, None]

    coords = list(ShapelyPoint(p) for p in line.coords)
    traveled = 0
    last_point = coords[0]
    for i, p in enumerate(coords[1:], 1):
        traveled += p.distance(last_point)
        last_point = p
        if traveled == distance:
            return [
                LineString(coords[:i + 1]),
                LineString(coords[i:])]
        if traveled > distance:
            cp = line.interpolate(distance)
            return [
                LineString(coords[:i] + [(cp.x, cp.y)]),
                LineString([(cp.x, cp.y)] + coords[i:])]


def roll_linear_ring(ring, distance, normalized=False):
    """Make a linear ring start at a different point.

    Example: A B C D E F G A -> D E F G A B C

    Same linear ring, different ordering of the coordinates.
    """

    if not isinstance(ring, LinearRing):
        # In case they handed us a LineString
        ring = LinearRing(ring)

    pieces = cut(LinearRing(ring), distance, normalized=False)

    if None in pieces:
        # We cut exactly at the start or end.
        return ring

    # The first and last point in a linear ring are duplicated, so we omit one
    # copy
    return LinearRing(pieces[1].coords[:] + pieces[0].coords[1:])


def reverse_line_string(line_string):
    return LineString(line_string.coords[::-1])


def ensure_multi_line_string(thing):
    """Given either a MultiLineString or a single LineString, return a MultiLineString"""

    if isinstance(thing, LineString):
        return MultiLineString([thing])
    else:
        return thing


def ensure_geometry_collection(thing):
    """Given either some kind of geometry or a GeometryCollection, return a GeometryCollection"""

    if isinstance(thing, (MultiLineString, MultiPolygon, MultiPoint)):
        return GeometryCollection(thing.geoms)
    elif isinstance(thing, GeometryCollection):
        return thing
    else:
        return GeometryCollection([thing])


def ensure_multi_polygon(thing):
    """Given either a MultiPolygon or a single Polygon, return a MultiPolygon"""

    if isinstance(thing, Polygon):
        return MultiPolygon([thing])
    else:
        return thing


def cut_path(points, length):
    """Return a subsection of at the start of the path that is length units long.

    Given a path denoted by a set of points, walk along it until we've travelled
    the specified length and return a new path up to that point.

    If the original path isn't that long, just return it as is.
    """

    if len(points) < 2:
        return points

    path = LineString(points)
    subpath, rest = cut(path, length)

    return [Point(*point) for point in subpath.coords]


def collapse_duplicate_point(geometry):
    if geometry.area < 0.01:
        return geometry.representative_point()

    return geometry


class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y

    @classmethod
    def from_shapely_point(cls, point):
        return cls(point.x, point.y)

    @classmethod
    def from_tuple(cls, point):
        return cls(point[0], point[1])

    def __json__(self):
        return vars(self)

    def __add__(self, other):
        return self.__class__(self.x + other.x, self.y + other.y)

    def __sub__(self, other):
        return self.__class__(self.x - other.x, self.y - other.y)

    def mul(self, scalar):
        return self.__class__(self.x * scalar, self.y * scalar)

    def __mul__(self, other):
        if isinstance(other, Point):
            # dot product
            return self.x * other.x + self.y * other.y
        elif isinstance(other, (int, float)):
            return self.__class__(self.x * other, self.y * other)
        else:
            raise ValueError("cannot multiply %s by %s" % (type(self), type(other)))

    def __neg__(self):
        return self * -1

    def __rmul__(self, other):
        if isinstance(other, (int, float)):
            return self.__mul__(other)
        else:
            raise ValueError("cannot multiply %s by %s" % (type(self), type(other)))

    def __truediv__(self, other):
        if isinstance(other, (int, float)):
            return self * (1.0 / other)
        else:
            raise ValueError("cannot divide %s by %s" % (type(self), type(other)))

    def __eq__(self, other):
        return self.x == other.x and self.y == other.y

    def __repr__(self):
        return "%s(%s,%s)" % (type(self), self.x, self.y)

    def length(self):
        return math.sqrt(math.pow(self.x, 2.0) + math.pow(self.y, 2.0))

    def distance(self, other):
        return (other - self).length()

    def unit(self):
        return self.mul(1.0 / self.length())

    def rotate_left(self):
        return self.__class__(-self.y, self.x)

    def rotate(self, angle):
        return self.__class__(self.x * math.cos(angle) - self.y * math.sin(angle), self.y * math.cos(angle) + self.x * math.sin(angle))

    def as_int(self):
        return self.__class__(int(round(self.x)), int(round(self.y)))

    def as_tuple(self):
        return (self.x, self.y)

    def __getitem__(self, item):
        return self.as_tuple()[item]

    def __len__(self):
        return 2


def line_string_to_point_list(line_string):
    return [Point(*point) for point in line_string.coords]