util.py 文件源码

def derampGMatrix(displ):
    """ Deramp through lsq a bilinear plane
    Data is also de-meaned
    """
    if displ.ndim != 2:
        raise TypeError('Displacement has to be 2-dim array')

    # form a relative coordinate grid
    c_grid = num.mgrid[0:displ.shape[0], 0:displ.shape[1]]

    # separate and flatten coordinate grid into x and y vectors for each !point
    ix = c_grid[0].flat
    iy = c_grid[1].flat
    displ_f = displ.flat

    # reduce vectors taking out all NaN's
    displ_nonan = displ_f[num.isfinite(displ_f)]
    ix = ix[num.isfinite(displ_f)]
    iy = iy[num.isfinite(displ_f)]

    # form kernel/design derampMatrix (c, x, y)
    GT = num.matrix([num.ones(len(ix)), ix, iy])
    G = GT.T

    # generalized kernel matrix (quadtratic)
    GTG = GT * G
    # generalized inverse
    GTGinv = GTG.I

    # lsq estimates of ramp parameter
    ramp_paras = displ_nonan * (GTGinv * GT).T

    # ramp values
    ramp_nonan = ramp_paras * GT
    ramp_f = num.multiply(displ_f, 0.)

    # insert ramp values in full vectors
    num.place(ramp_f, num.isfinite(displ_f), num.array(ramp_nonan).flatten())
    ramp_f = ramp_f.reshape(displ.shape[0], displ.shape[1])

    return displ - ramp_f