gnuplot image code

[Quentin Spencer]

Attached is a modified version of Dan's code for displaying images in 
gnuplot (versions >=4.1). I have reorganized the code a bit, but I put 
Dan's name in the copyright notice, since what I did was mostly cutting 
and pasting. I'm including 3 files: a patch to image.m, 
__gnuplot_version__.m, which returns the version of gnuplot, and 
__img__.m, the low-level interface with gnuplot. I have opted to put 
only the gnuplot specific code in __img__.

Quentin

Index: scripts/image/image.m
===================================================================
RCS file: /cvs/octave/scripts/image/image.m,v
retrieving revision 1.26
diff -u -r1.26 image.m
--- scripts/image/image.m       10 Oct 2006 16:10:27 -0000      1.26
+++ scripts/image/image.m       19 Oct 2006 19:25:05 -0000
@@ -57,35 +57,40 @@
     print_usage ();
   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);
+  if __gnuplot_version__ > 4.0
+    __img__ (x, y, A);
+  else
+
+    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
-  endif
-  ppm_name = tmpnam ();
+    ppm_name = tmpnam ();
 
-  saveimage (ppm_name, A, "ppm");
+    saveimage (ppm_name, A, "ppm");
 
-  ## Start the viewer.  Try display, xv, then xloadimage.
+    ## Start the viewer.  Try display, xv, then xloadimage.
 
-  xv = sprintf ("xv -raw -expand %f \"%s\"", zoom, ppm_name);
+    xv = sprintf ("xv -raw -expand %f \"%s\"", zoom, ppm_name);
 
-  xloadimage = sprintf ("xloadimage -zoom %f \"%s\"", zoom*100, ppm_name);
+    xloadimage = sprintf ("xloadimage -zoom %f \"%s\"", zoom*100, ppm_name);
 
-  ## ImageMagick:
-  im_display = sprintf ("display -geometry %f%% \"%s\"", zoom*100, ppm_name);
+    ## ImageMagick:
+    im_display = sprintf ("display -geometry %f%% \"%s\"", zoom*100, ppm_name);
   
-  rm = sprintf ("rm -f \"%s\"", ppm_name);
+    rm = sprintf ("rm -f \"%s\"", ppm_name);
 
-  ## Need to let the shell clean up the tmp file because we are putting
-  ## the viewer in the background.
+    ## Need to let the shell clean up the tmp file because we are putting
+    ## the viewer in the background.
 
-  system (sprintf ("( %s || %s || %s && %s ) > /dev/null 2>&1 &",
-                   im_display, xv, xloadimage, rm));
+    system (sprintf ("( %s || %s || %s && %s ) > /dev/null 2>&1 &",
+                     im_display, xv, xloadimage, rm));
+  endif
 
 endfunction

## Copyright (C) 2006 Daniel Sebald
##
## 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 -*-
## @deftypefn {Function File} { @var{version} = } __gnuplot_version__
## Returns the version of gnuplot.
## @end deftypefn

function version = __gnuplot_version__

  persistent __version__ = 0;

  if !__version__
    ## If the function hasn't been called before, use this code to get
    ## the version from gnuplot.
    [status, output] = system([gnuplot_binary, " --version"]);
    words = split(output, " ");
    if ( (size (words,1) >= 2) && isdigit (words(2,1)) )
      __version__ = sscanf(words(2,:), "%f", 1);
    else
      __version__ = -1;
    endif
  endif

  version = __version__;

endfunction

## Copyright (C) 2006 Daniel Sebald
##
## 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 -*-
## @deftypefn {Function File} {} __img__ (@var{x}, @var{y}, @var{A})
## Display an image using @code{gnuplot}, where vectors @var{x} and
## @var{y} define the axes and the matrix @var{A} contains the image
## data.
## @end deftypefn

function __img__ (x, y, A)

  if (nargin ~= 3)
    print_usage ();
  endif

  if (isempty(A))
    error("Image matrix is empty.");
  endif

  __gnuplot_raw__ ("set nokey\n");
  __current_color_map__ = colormap ();
  palette_size = size (__current_color_map__, 1);
  __gnuplot_raw__ (sprintf ("set palette positive color model RGB maxcolors 
%i\n", palette_size));
  if (palette_size <= 128)
    ## Break up command to avoid buffer overflow.
    __gnuplot_raw__ ("set palette file \"-\"\n");
    for i = 1:palette_size
      __gnuplot_raw__ (sprintf ("%g %g %g %g\n", 1e-3 * round (1e3 * 
[(i-1)/(palette_size-1) __current_color_map__(i,:)])));
    end
    __gnuplot_raw__("e\n");
  else
    ## Let the file be deleted when Octave exits or `purge_tmp_files' is called.
    [fid, binary_file_name, msg] = mkstemp([P_tmpdir,"/gpimageXXXXXX"], 1);
    fwrite(fid, __current_color_map__', "float32", 0, "ieee-le");
    fclose(fid);
    __gnuplot_raw__ (sprintf ("set palette file \"%s\" binary record=%d using 
1:2:3\n", binary_file_name, palette_size));
  endif

  ## Use the newly added mode of "plot" called "with image".
  if (isempty(x))
    x = [1 size(A,2)];
    y = [1 size(A,1)];
  endif

  ## Force rectangular grid by using only end points of
  ## first row (column) if x (y) is a matrix or vector.
  if ((size(x,2)) > 1)
    x = x(1,:)';
  endif
  if (abs(x(end) - x(1)) < (10*eps))
    error ("End points in x dimension must not be equal.");
  else
    x_dim = size(A,2);
    if (x_dim > 1)
      dx = (x(end)-x(1))/(x_dim-1);
    else
      dx = 1;
    endif
  endif
  if ((size(y,1)) > 1)
    y = y(:,1)';
  endif
  if (abs(y(end) - y(1)) < 10*eps)
    error ("End points in y dimension must not be equal.");
  else
    y_dim = size(A,1);
    if (y_dim > 1)
      dy = (y(end)-y(1))/(y_dim-1);
    else
      dy = 1;
    endif
  endif

  __gnuplot_raw__ (sprintf ("set xrange [%g:%g]\n", x(1)-dx/2, x(end)+dx/2));
  __gnuplot_raw__ (sprintf ("set yrange [%g:%g]\n", y(1)-dy/2, y(end)+dy/2));
  __gnuplot_raw__ ("set autoscale fix\n"); # "fix" is helpful for "a" hotkey
  __gnuplot_raw__ ("set tics out\n");

  A = reshape(A,size(A,1)*size(A,2),1);
  ## Let the file be deleted when Octave exits or `purge_tmp_files' is called.
  [fid, binary_file_name, msg] = mkstemp ([P_tmpdir, "/gpimageXXXXXX"], 1);
  ## Gnuplot reads binary files very quickly.  However, the 'fwrite' below
  ## is much slower than using the current '__gnuplot_plot__' command.
  fwrite(fid, A', "float", 0, "ieee-le");
  fclose(fid);
  __gnuplot_raw__ (sprintf ("plot \"%s\" binary array=%dx%d scan=yx flipy 
origin=(%g,%g) dx=%g dy=%g endian=little using 1 with image\n", 
binary_file_name, x_dim, y_dim, min (x(1), x(end)), min(y(1), y(end)), abs 
(dx), abs (dy)));
  ## Put back in default data mode.
  __gnuplot_raw__ ("set xrange [*:*];\n");
  __gnuplot_raw__ ("set yrange [*:*];\n");

endfunction