imdata.py 文件源码

def _aipscc(self, threshold=None, relative=True,
                    istokes=0, ifreq=0):
        '''
        Make AIPS CC table

        Arguments:
            istokes (integer): index for Stokes Parameter at which the image will be saved
            ifreq (integer): index for Frequency at which the image will be saved
            threshold (float): pixels with the absolute intensity smaller than this value will be ignored.
            relative (boolean): If true, theshold value will be normalized with the peak intensity of the image.
        '''
        Nx = self.header["nx"]
        Ny = self.header["ny"]
        xg, yg = self.get_xygrid(angunit="deg")
        X, Y = np.meshgrid(xg, yg)
        X = X.reshape(Nx * Ny)
        Y = Y.reshape(Nx * Ny)
        flux = self.data[istokes, ifreq]
        flux = flux.reshape(Nx * Ny)

        # threshold
        if threshold is None:
            thres = np.finfo(np.float32).eps
        else:
            if relative:
                thres = self.peak(istokes=istokes, ifreq=ifreq) * threshold
            else:
                thres = threshold
        thres = np.abs(thres)

        # adopt threshold
        X = X[flux >= thres]
        Y = Y[flux >= thres]
        flux = flux[flux >= thres]

        # make table columns
        c1 = pyfits.Column(name='FLUX', array=flux, format='1E',unit='JY')
        c2 = pyfits.Column(name='DELTAX', array=X, format='1E',unit='DEGREES')
        c3 = pyfits.Column(name='DELTAY', array=Y, format='1E',unit='DEGREES')
        c4 = pyfits.Column(name='MAJOR AX', array=np.zeros(len(flux)), format='1E',unit='DEGREES')
        c5 = pyfits.Column(name='MINOR AX', array=np.zeros(len(flux)), format='1E',unit='DEGREES')
        c6 = pyfits.Column(name='POSANGLE', array=np.zeros(len(flux)), format='1E',unit='DEGREES')
        c7 = pyfits.Column(name='TYPE OBJ', array=np.zeros(len(flux)), format='1E',unit='CODE')

        # make CC table
        tab = pyfits.BinTableHDU.from_columns([c1, c2, c3, c4, c5, c6, c7])
        return tab