healpix.py 文件源码

def pix2ang_ring(nside, ipix):
    """Calculate the angular coordinates on the sphere for each pixel
    index in the RING ordering scheme.

    Parameters
    ----------
    ipix : 1D or 2D `~numpy.ndarray`
        The indexes of the HEALPix pixels in the RING ordering

    Returns
    -------
    theta : 1D or 2D `~numpy.ndarray`
        The polar angles (i.e., latitudes), ? ? [0, ?]. (unit: rad)
    phi : 1D or 2D `~numpy.ndarray`
        The azimuthal angles (i.e., longitudes), ? ? [0, 2?). (unit: rad)
        The shape is the same as the input array.

    NOTE
    ----
    * Only support the *RING* ordering scheme
    * This is the JIT-optimized version that partially replaces the
      ``healpy.pix2ang``
    """
    shape = ipix.shape
    size = ipix.size
    ipix = ipix.flatten()
    theta = np.zeros(size, dtype=np.float64)
    phi = np.zeros(size, dtype=np.float64)
    for i in range(size):
        theta_, phi_ = pix2ang_ring_single(nside, ipix[i])
        theta[i] = theta_
        phi[i] = phi_
    return (theta.reshape(shape), phi.reshape(shape))