; TVHXF
;---------------------------------------------------------------
;! Task to calculate transfer function based on histogram
;# TASK TV
;-----------------------------------------------------------------------
;;  Copyright (C) 1995
;;  Associated Universities, Inc. Washington DC, USA.
;;
;;  This program is free software; you can redistribute it and/or
;;  modify it under the terms of the GNU General Public License as
;;  published by the Free Software Foundation; either version 2 of
;;  the License, or (at your option) any later version.
;;
;;  This program is distributed in the hope that it will be useful,
;;  but WITHOUT ANY WARRANTY; without even the implied warranty of
;;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;;  GNU General Public License for more details.
;;
;;  You should have received a copy of the GNU General Public
;;  License along with this program; if not, write to the Free
;;  Software Foundation, Inc., 675 Massachusetts Ave, Cambridge,
;;  MA 02139, USA.
;;
;;  Correspondence concerning AIPS should be addressed as follows:
;;         Internet email: aipsmail@nrao.edu.
;;         Postal address: AIPS Project Office
;;                         National Radio Astronomy Observatory
;;                         520 Edgemont Road
;;                         Charlottesville, VA 22903-2475 USA
;-----------------------------------------------------------------------
;---------------------------------------------------------------
TVHXF     LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC
TVHXF:  Task to calculate transfer function based on histogram
TVCHAN          0.0        99.0    Image plane to work on
                                     <1 => 1
                                     >(no. of planes present)
                                        => 1
----------------------------------------------------------------
TVHXF
Type: Task
Use:  TVHXF calculates a TV transfer function based on histogram
      equalization.  This maximizes the dynamic range visible.
      The back ground may be removed, i.e., all pixels below a
      certain pixel value are made invisible; the rejection
      level is controlled by the cursor.  The peak of the
      intensity histogram is given each time a new histogram is
      calculated.  Button A switches between a quasi-linear and
      a logarithmic equalization; "linear" favors the lower
      intensities, "logarithmic" the higher ones.  Button B
      switches between spectrum colors and gray scale.  Button C
      controls the zoom, and Button D causes exit.
      At the top of the screen are shown: the equalization
      function, the position of the peak in the histogram, and
      the current back ground rejection level.
      Note that the histogram is based on the screen picture,
      and is thus affected by the zoom.
----------------------------------------------------------------
