scikit-image

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#cython: cdivision=True
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#cython: nonecheck=False
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#cython: wraparound=False
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import numpy as np
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cimport numpy as cnp
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from .._shared.fused_numerics cimport np_floats
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cnp.import_array()
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def moments_hu(np_floats[:, :] nu):
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    if np_floats is cnp.float32_t:
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        dtype = np.float32
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    else:
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        dtype = np.float64
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    cdef np_floats[::1] hu = np.zeros((7,), dtype=dtype)
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    cdef np_floats t0 = nu[3, 0] + nu[1, 2]
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    cdef np_floats t1 = nu[2, 1] + nu[0, 3]
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    cdef np_floats q0 = t0 * t0
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    cdef np_floats q1 = t1 * t1
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    cdef np_floats n4 = 4 * nu[1, 1]
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    cdef np_floats s = nu[2, 0] + nu[0, 2]
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    cdef np_floats d = nu[2, 0] - nu[0, 2]
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    hu[0] = s
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    hu[1] = d * d + n4 * nu[1, 1]
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    hu[3] = q0 + q1
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    hu[5] = d * (q0 - q1) + n4 * t0 * t1
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    t0 *= q0 - 3 * q1
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    t1 *= 3 * q0 - q1
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    q0 = nu[3, 0]- 3 * nu[1, 2]
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    q1 = 3 * nu[2, 1] - nu[0, 3]
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    hu[2] = q0 * q0 + q1 * q1
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    hu[4] = q0 * t0 + q1 * t1
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    hu[6] = q1 * t0 - q0 * t1
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    return np.asarray(hu)
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