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- import numpy as np
- def _round_safe(coords):
- """Round coords while ensuring successive values are less than 1 apart.
- When rounding coordinates for `line_nd`, we want coordinates that are less
- than 1 apart (always the case, by design) to remain less than one apart.
- However, NumPy rounds values to the nearest *even* integer, so:
- >>> np.round([0.5, 1.5, 2.5, 3.5, 4.5])
- array([0., 2., 2., 4., 4.])
- So, for our application, we detect whether the above case occurs, and use
- ``np.floor`` if so. It is sufficient to detect that the first coordinate
- falls on 0.5 and that the second coordinate is 1.0 apart, since we assume
- by construction that the inter-point distance is less than or equal to 1
- and that all successive points are equidistant.
- Parameters
- ----------
- coords : 1D array of float
- The coordinates array. We assume that all successive values are
- equidistant (``np.all(np.diff(coords) = coords[1] - coords[0])``)
- and that this distance is no more than 1
- (``np.abs(coords[1] - coords[0]) <= 1``).
- Returns
- -------
- rounded : 1D array of int
- The array correctly rounded for an indexing operation, such that no
- successive indices will be more than 1 apart.
- Examples
- --------
- >>> coords0 = np.array([0.5, 1.25, 2., 2.75, 3.5])
- >>> _round_safe(coords0)
- array([0, 1, 2, 3, 4])
- >>> coords1 = np.arange(0.5, 8, 1)
- >>> coords1
- array([0.5, 1.5, 2.5, 3.5, 4.5, 5.5, 6.5, 7.5])
- >>> _round_safe(coords1)
- array([0, 1, 2, 3, 4, 5, 6, 7])
- """
- if len(coords) > 1 and coords[0] % 1 == 0.5 and coords[1] - coords[0] == 1:
- _round_function = np.floor
- else:
- _round_function = np.round
- return _round_function(coords).astype(int)
- def line_nd(start, stop, *, endpoint=False, integer=True):
- """Draw a single-pixel thick line in n dimensions.
- The line produced will be ndim-connected. That is, two subsequent
- pixels in the line will be either direct or diagonal neighbors in
- n dimensions.
- Parameters
- ----------
- start : array-like, shape (N,)
- The start coordinates of the line.
- stop : array-like, shape (N,)
- The end coordinates of the line.
- endpoint : bool, optional
- Whether to include the endpoint in the returned line. Defaults
- to False, which allows for easy drawing of multi-point paths.
- integer : bool, optional
- Whether to round the coordinates to integer. If True (default),
- the returned coordinates can be used to directly index into an
- array. `False` could be used for e.g. vector drawing.
- Returns
- -------
- coords : tuple of arrays
- The coordinates of points on the line.
- Examples
- --------
- >>> lin = line_nd((1, 1), (5, 2.5), endpoint=False)
- >>> lin
- (array([1, 2, 3, 4]), array([1, 1, 2, 2]))
- >>> im = np.zeros((6, 5), dtype=int)
- >>> im[lin] = 1
- >>> im
- array([[0, 0, 0, 0, 0],
- [0, 1, 0, 0, 0],
- [0, 1, 0, 0, 0],
- [0, 0, 1, 0, 0],
- [0, 0, 1, 0, 0],
- [0, 0, 0, 0, 0]])
- >>> line_nd([2, 1, 1], [5, 5, 2.5], endpoint=True)
- (array([2, 3, 4, 4, 5]), array([1, 2, 3, 4, 5]), array([1, 1, 2, 2, 2]))
- """
- start = np.asarray(start)
- stop = np.asarray(stop)
- npoints = int(np.ceil(np.max(np.abs(stop - start))))
- if endpoint:
- npoints += 1
- coords = np.linspace(start, stop, num=npoints, endpoint=endpoint).T
- if integer:
- for dim in range(len(start)):
- coords[dim, :] = _round_safe(coords[dim, :])
- coords = coords.astype(int)
- return tuple(coords)
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