JIVE Wiki

def get_small_source_stats_main(aips_image, \
                                source_radius, noise_inner_radius, \
                                noise_outer_radius, edge_width=10, \
                                print_level=1):
    """User version for statistis from an image for a \"small\" source.
 
    This function takes an AIPSImage, and returns physical (Jy/beam and Jy)
    values.  Note that the returned position is a C position!!!
 
    This function will inspect an image to locate a single, strong,
    mostly circular-ish source.  The source will be found from the
    strongest pixel in the image, excluding edge pixels.  This function
    will the conpute the integrated source brightness within source_radius
    pixels of the max pixel, and the RMS noise level for pixels at least
    noise_radius pixels away from max, again, excluding edge pixels.
 
    aips_image     I  the incoming image as an AIPSImage
 
    source_radius  I  the radius from the center of the source to sum pixels
 
    noise_inner_radius I  inner radius of an annulus to calculate the noise level
 
    noise_outer_radius I  outer radius of an annulus to calculate the noise level
 
    edge_width     I  width in pixels to avoid at the edge of the image
 
    print_level    I  how much should the user be informed.
                      0  None
                      1  Some
 
    It returns information as (max, max_pos, sum, rms), where
    max is the maximum pixel value, in specific intensity (Jy/beam)
    max_pos is the position list (array) [y,x] of the maximum pixel position
    sum is the integrated brightness of the source (may be affected by
        previous masking of pixels).  Note that this function returns the
        sum in flux density (Jy) units, 
    rms is the RMS value off-source for pixels in radius range
        noise_inner_radius to noise_outer_radius (Jy/beam)
    """
    # Get a Wizardry image to work on the pixels
    w = Wizardry.AIPSData.AIPSImage(aips_image.name, aips_image.klass, \
                                    aips_image.disk, aips_image.seq)
    # make a masked array
    x = numarray.ma.array(w.pixels.copy(), \
                          mask=numarray.ma.make_mask_none((aips_image.header.naxis[1],aips_image.header.naxis[0])))
    (image_max, image_max_pos, image_sum, image_rms) = \
                get_small_source_stats(x, source_radius,
                                       noise_inner_radius, noise_outer_radius,
                                       print_level)
    # Now correct the sum for the beam size
    factor = aips_image.header.bmaj * aips_image.header.bmin / \
             math.fabs(aips_image.header.cdelt[1] * aips_image.header.cdelt[0])
    image_sum = image_sum / factor
    if(print_level > 0):
        print 'Got information from image of:'
        print 'Max:', image_max
        print 'Pos:', image_max_pos
        print 'Sum:', image_sum
        print 'RMS:', image_rms
    return (image_max, image_max_pos, image_sum, image_rms)