From octave-sources-request at bevo dot che dot wisc dot edu Fri Jan 10 17:59:01 2003
Subject: image.m that reuses window
From: "Joshua L. Cherry" <cherry at oeb dot harvard dot edu>
To: <octave-sources at bevo dot che dot wisc dot edu>
Date: Fri, 10 Jan 2003 18:50:56 -0500 (EST)

The image command in octave brings up a new window each time it's called,
so image windows accumulate.  Usually it would be preferable for a single
window to be reused.  I've modified the image code to launch xv once and
use the same instance repeatedly.  The trick is that sending xv the QUIT
signal makes it reread its file.

Josh Cherry



-------------------begin image.m---------------

## Copyright (C) 1996, 1997 John W. Eaton
##
## This file is part of Octave.
##
## Octave 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, or (at your option)
## any later version.
##
## Octave 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 Octave; see the file COPYING.  If not, write to the Free
## Software Foundation, 59 Temple Place - Suite 330, Boston, MA
## 02111-1307, USA.

## -*- texinfo -*-
##  at deftypefn {Function File} {} image (@var{x}, @var{zoom})
##  at deftypefnx {Function File} {} image (@var{x}, @var{y}, @var{A}, @var{zoom})
## Display a matrix as a color image.  The elements of  at var{x} are indices
## into the current colormap and should have values between 1 and the
## length of the colormap.  If  at var{zoom} is omitted, the image will be
## scaled to fit within 600x350 (to a max of 4).
##
## The axis values corresponding to the matrix elements are specified in
##  at var{x} and @var{y}. At present they are ignored.
##  at end deftypefn
##  at seealso{imshow, imagesc, and colormap}

## Author: Tony Richardson <arichard at stark dot cc dot oh dot us>
## Created: July 1994
## Adapted-By: jwe

## Modified by Josh Cherry <cherry at oeb dot harvard dot edu>
## to use xv's reload feature (upon signal -QUIT)
## so that the same window is reused
## January 2003

function image (x, y, A, zoom)

  if (nargin == 0)
    ## Load Bobbie Jo Richardson (Born 3/16/94)
    x = loadimage ("default.img");
    zoom = 2;
  elseif (nargin == 1)
    A = x;
    zoom = [];
    x=y=[];
  elseif (nargin == 2)
    A = x;
    zoom = y;
    x=y=[];
  elseif (nargin == 3)
    zoom = [];
  elseif (nargin > 4)
    usage ("image (matrix, [zoom]) or image (x, y, matrix, [zoom])");
  endif

  if isempty(zoom)
    ## Find an integer scale factor which sets the image to
    ## approximately the size of the screen.
    zoom = min([350/rows(A), 600/columns(A), 4]);
    if zoom>=1
      zoom=floor(zoom);
    else
      zoom=1/ceil(1/zoom);
    endif
  endif

  # use old temp file name if it exists
  global __image_ppm_name__;
  if (!exist("__image_ppm_name__"))
    __image_ppm_name__ = tmpnam ();
  end

  saveimage (__image_ppm_name__, A, "ppm");

  [output, status] = system("which xv", 1);   # is xv available?
  if (status)       # no xv; fall back on xloadimage
    xloadimage = sprintf ("xloadimage -zoom %f %s", zoom*100, __image_ppm_name__);
    system(xloadimage, 1, "async");
  else              # use xv
    # determine whether xv is already running
    global __image_xv_pid__;
    if (!exist("__image_xv_pid__"))
      running = 0;                         # first time image called
    else
      if (waitpid(__image_xv_pid__, 1))    # process defunct or no longer running
	running = 0;
      else
	running = 1;
      end
    end

    if (!running)       # xv not running; start it
      xv = sprintf ("xv -expand %f -raw %s", zoom, __image_ppm_name__);
      __image_xv_pid__ = system (xv, 1, "async");
    else              # xv already started; send QUIT signal
      kill = sprintf("kill -QUIT %d", __image_xv_pid__);
      system(kill);
    end
  end
  # this version does not remove the temp file __image_ppm_name__

endfunction