mirror of
https://github.com/wassname/scikit-image.git
synced 2026-06-29 06:33:19 +08:00
Stefan van der Walt
75 lines
2.1 KiB
Python
75 lines
2.1 KiB
Python
from __future__ import division
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import numpy as np
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from ._warp import warp
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def _swirl_mapping(xy, center, rotation, strength, radius):
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x, y = xy.T
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x0, y0 = center
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rho = np.sqrt((x - x0)**2 + (y - y0)**2)
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# Ensure that the transformation decays to approximately 1/1000-th
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# within the specified radius.
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radius = radius / 5 * np.log(2)
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theta = rotation + strength * \
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np.exp(-rho / radius) + \
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np.arctan2(y - y0, x - x0)
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xy[..., 0] = x0 + rho * np.cos(theta)
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xy[..., 1] = y0 + rho * np.sin(theta)
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return xy
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def swirl(image, center=None, strength=1, radius=100, rotation=0,
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output_shape=None, order=1, mode='constant', cval=0):
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"""Perform a swirl transformation.
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Parameters
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----------
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image : ndarray
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Input image.
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center : (x,y) tuple or (2,) ndarray
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Center coordinate of transformation.
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strength : float
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The amount of swirling applied.
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radius : float
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The extent of the swirl in pixels. The effect dies out
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rapidly beyond `radius`.
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rotation : float
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Additional rotation applied to the image.
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Returns
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-------
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swirled : ndarray
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Swirled version of the input.
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Other parameters
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----------------
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output_shape : tuple or ndarray
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Size of the generated output image.
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order : int
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Order of splines used in interpolation. See
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`scipy.ndimage.map_coordinates` for detail.
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mode : string
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How to handle values outside the image borders. See
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`scipy.ndimage.map_coordinates` for detail.
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cval : string
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Used in conjunction with mode 'constant', the value outside
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the image boundaries.
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"""
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if center is None:
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center = np.array(image.shape)[:2] / 2
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warp_args = {'center': center,
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'rotation': rotation,
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'strength': strength,
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'radius': radius}
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return warp(image, _swirl_mapping, map_args=warp_args,
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output_shape=output_shape,
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order=order, mode=mode, cval=cval)
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