helper.py 文件源码

def nufft_scale1(N, K, alpha, beta, Nmid):
    '''
    Calculate image space scaling factor
    '''
#     import types
#     if alpha is types.ComplexType:
    alpha = numpy.real(alpha)
#         print('complex alpha may not work, but I just let it as')

    L = len(alpha) - 1
    if L > 0:
        sn = numpy.zeros((N, 1))
        n = numpy.arange(0, N).reshape((N, 1), order='F')
        i_gam_n_n0 = 1j * (2 * numpy.pi / K) * (n - Nmid) * beta
        for l1 in range(-L, L + 1):
            alf = alpha[abs(l1)]
            if l1 < 0:
                alf = numpy.conj(alf)
            sn = sn + alf * numpy.exp(i_gam_n_n0 * l1)
    else:
        sn = numpy.dot(alpha, numpy.ones((N, 1)))
    return sn