Return the catalog pixels spanned by this ROI.

def getCatalogPixels(self):
        """
        Return the catalog pixels spanned by this ROI.
        """
        filenames = self.config.getFilenames()

        nside_catalog = self.config.params['coords']['nside_catalog']
        nside_pixel = self.config.params['coords']['nside_pixel']
        # All possible catalog pixels spanned by the ROI
        superpix = ugali.utils.skymap.superpixel(self.pixels,nside_pixel,nside_catalog)
        superpix = np.unique(superpix)
        # Only catalog pixels that exist in catalog files
        pixels = np.intersect1d(superpix, filenames['pix'].compressed())
        return pixels