Source code for pymunk.autogeometry

"""This module contain functions for automatic generation of geometry, for 
example from an image.

Example::

    >>> import pymunk
    >>> from pymunk.autogeometry import march_soft
    >>> img = [
    ...     "  xx   ",
    ...     "  xx   ",
    ...     "  xx   ",
    ...     "  xx   ",
    ...     "  xx   ",
    ...     "  xxxxx",
    ...     "  xxxxx",
    ... ]
    >>> def sample_func(point):
    ...     x = int(point[0])
    ...     y = int(point[1])
    ...     return 1 if img[y][x] == "x" else 0

    >>> pl_set = march_soft(pymunk.BB(0,0,6,6), 7, 7, .5, sample_func)
    >>> print(len(pl_set))
    2

The information in segments can now be used to create geometry, for example as 
a Pymunk Poly or Segment::

    >>> s = pymunk.Space()
    >>> for poly_line in pl_set:
    ...     for i in range(len(poly_line) - 1):
    ...         a = poly_line[i]
    ...         b = poly_line[i + 1]
    ...         segment = pymunk.Segment(s.static_body, a, b, 1)  
    ...         s.add(segment)


"""
__docformat__ = "reStructuredText"

from typing import TYPE_CHECKING, Callable, List, Sequence, Tuple, Union, overload

if TYPE_CHECKING:
    from .bb import BB

from ._chipmunk_cffi import ffi, lib
from .vec2d import Vec2d

_SegmentFunc = Callable[[Tuple[float, float], Tuple[float, float]], None]
_SampleFunc = Callable[[Tuple[float, float]], float]

_Polyline = Union[List[Tuple[float, float]], List[Vec2d]]
# Union is needed since List is invariant
# and Sequence cant be used since CFFI requires a List (or Tuple)


def _to_chipmunk(polyline: _Polyline) -> ffi.CData:
    l = len(polyline)
    _line = ffi.new("cpPolyline *", {"verts": l})
    _line.count = l
    _line.capacity = l
    _line.verts = polyline
    return _line


def _from_polyline_set(_set: ffi.CData) -> List[List[Vec2d]]:
    lines = []
    for i in range(_set.count):
        line = []
        l = _set.lines[i]
        for j in range(l.count):
            line.append(Vec2d(l.verts[j].x, l.verts[j].y))
        lines.append(line)
    return lines


[docs]def is_closed(polyline: _Polyline) -> bool: """Returns true if the first vertex is equal to the last. :param polyline: Polyline to simplify. :type polyline: [(float,float)] :rtype: `bool` """ return bool(lib.cpPolylineIsClosed(_to_chipmunk(polyline)))
[docs]def simplify_curves(polyline: _Polyline, tolerance: float) -> List[Vec2d]: """Returns a copy of a polyline simplified by using the Douglas-Peucker algorithm. This works very well on smooth or gently curved shapes, but not well on straight edged or angular shapes. :param polyline: Polyline to simplify. :type polyline: [(float,float)] :param float tolerance: A higher value means more error is tolerated. :rtype: [(float,float)] """ _line = lib.cpPolylineSimplifyCurves(_to_chipmunk(polyline), tolerance) simplified = [] for i in range(_line.count): simplified.append(Vec2d(_line.verts[i].x, _line.verts[i].y)) return simplified
[docs]def simplify_vertexes(polyline: _Polyline, tolerance: float) -> List[Vec2d]: """Returns a copy of a polyline simplified by discarding "flat" vertexes. This works well on straight edged or angular shapes, not as well on smooth shapes. :param polyline: Polyline to simplify. :type polyline: [(float,float)] :param float tolerance: A higher value means more error is tolerated. :rtype: [(float,float)] """ _line = lib.cpPolylineSimplifyVertexes(_to_chipmunk(polyline), tolerance) simplified = [] for i in range(_line.count): simplified.append(Vec2d(_line.verts[i].x, _line.verts[i].y)) return simplified
[docs]def to_convex_hull(polyline: _Polyline, tolerance: float) -> List[Vec2d]: """Get the convex hull of a polyline as a looped polyline. :param polyline: Polyline to simplify. :type polyline: [(float,float)] :param float tolerance: A higher value means more error is tolerated. :rtype: [(float,float)] """ _line = lib.cpPolylineToConvexHull(_to_chipmunk(polyline), tolerance) hull = [] for i in range(_line.count): hull.append(Vec2d(_line.verts[i].x, _line.verts[i].y)) return hull
[docs]def convex_decomposition(polyline: _Polyline, tolerance: float) -> List[List[Vec2d]]: """Get an approximate convex decomposition from a polyline. Returns a list of convex hulls that match the original shape to within tolerance. .. note:: If the input is a self intersecting polygon, the output might end up overly simplified. :param polyline: Polyline to simplify. :type polyline: [(float,float)] :param float tolerance: A higher value means more error is tolerated. :rtype: [(float,float)] """ _line = _to_chipmunk(polyline) _set = lib.cpPolylineConvexDecomposition(_line, tolerance) return _from_polyline_set(_set)
[docs]class PolylineSet(Sequence[List[Vec2d]]): """A set of Polylines. Mainly intended to be used for its :py:meth:`collect_segment` function when generating geometry with the :py:func:`march_soft` and :py:func:`march_hard` functions. """
[docs] def __init__(self) -> None: """Initalize a new PolylineSet""" def free(_set: ffi.CData) -> None: lib.cpPolylineSetFree(_set, True) self._set = ffi.gc(lib.cpPolylineSetNew(), free)
[docs] def collect_segment(self, v0: Tuple[float, float], v1: Tuple[float, float]) -> None: """Add a line segment to a polyline set. A segment will either start a new polyline, join two others, or add to or loop an existing polyline. This is mostly intended to be used as a callback directly from :py:func:`march_soft` or :py:func:`march_hard`. :param v0: Start of segment :type v0: (float,float) :param v1: End of segment :type v1: (float,float) """ assert len(v0) == 2 assert len(v1) == 2 lib.cpPolylineSetCollectSegment(v0, v1, self._set)
def __len__(self) -> int: return self._set.count @overload def __getitem__(self, index: int) -> List[Vec2d]: ... @overload def __getitem__(self, index: slice) -> "PolylineSet": ... def __getitem__(self, key: Union[int, slice]) -> Union[List[Vec2d], "PolylineSet"]: assert not isinstance(key, slice), "Slice indexing not supported" if key >= self._set.count: raise IndexError line = [] l = self._set.lines[key] for i in range(l.count): line.append(Vec2d(l.verts[i].x, l.verts[i].y)) return line
[docs]def march_soft( bb: "BB", x_samples: int, y_samples: int, threshold: float, sample_func: _SampleFunc, ) -> PolylineSet: """Trace an *anti-aliased* contour of an image along a particular threshold. The given number of samples will be taken and spread across the bounding box area using the sampling function and context. :param BB bb: Bounding box of the area to sample within :param int x_samples: Number of samples in x :param int y_samples: Number of samples in y :param float threshold: A higher value means more error is tolerated :param sample_func: The sample function will be called for x_samples * y_samples spread across the bounding box area, and should return a float. :type sample_func: ``func(point: Tuple[float, float]) -> float`` :return: PolylineSet with the polylines found. """ pl_set = PolylineSet() @ffi.callback("cpMarchSegmentFunc") def _seg_f(v0: ffi.CData, v1: ffi.CData, _data: ffi.CData) -> None: pl_set.collect_segment((v0.x, v0.y), (v1.x, v1.y)) @ffi.callback("cpMarchSampleFunc") def _sam_f(point: ffi.CData, _data: ffi.CData) -> float: # print("SAMPLE", point.x, point.y) return sample_func((point.x, point.y)) lib.cpMarchSoft( bb, x_samples, y_samples, threshold, _seg_f, ffi.NULL, _sam_f, ffi.NULL ) return pl_set
[docs]def march_hard( bb: "BB", x_samples: int, y_samples: int, threshold: float, sample_func: _SampleFunc, ) -> PolylineSet: """Trace an *aliased* curve of an image along a particular threshold. The given number of samples will be taken and spread across the bounding box area using the sampling function and context. :param BB bb: Bounding box of the area to sample within :param int x_samples: Number of samples in x :param int y_samples: Number of samples in y :param float threshold: A higher value means more error is tolerated :param sample_func: The sample function will be called for x_samples * y_samples spread across the bounding box area, and should return a float. :type sample_func: ``func(point: Tuple[float, float]) -> float`` :return: PolylineSet with the polylines found. """ pl_set = PolylineSet() @ffi.callback("cpMarchSegmentFunc") def _seg_f(v0: ffi.CData, v1: ffi.CData, _data: ffi.CData) -> None: pl_set.collect_segment((v0.x, v0.y), (v1.x, v1.y)) @ffi.callback("cpMarchSampleFunc") def _sam_f(point: ffi.CData, _data: ffi.CData) -> float: return sample_func((point.x, point.y)) lib.cpMarchHard( bb, x_samples, y_samples, threshold, _seg_f, ffi.NULL, _sam_f, ffi.NULL ) return pl_set