From help-octave-request at bevo dot che dot wisc dot edu  Sat Dec 23 18:10:52 2000
Subject: tv.m and tvs.m
From: Steve Mann <mann at eecg dot toronto dot edu>
To: help-octave at bevo dot che dot wisc dot edu
Cc: mann at eecg dot toronto dot edu
Date: 	Sat, 23 Dec 2000 19:10:25 -0500

because imshow doesn't work for color images in octave,
here's a simple script i wrote that might be of use, since it's
a quick hack to display color images in octave (feel free to
use and consider GPL version 2 if desired).

i'll still be now working on a way to print from octave, unless
someone else has already come up with a quick hack to print form
octave.

% tv.m based on a Matlab cmex program I wrote to display images in Matlab,
% although this is a quick hack (e.g. tempfiles, system() to image viewer).
% inspired by pv-wave's "tv" command   -- mann at eecg dot toronto dot edu
function tv(r,g,b);
fd = fopen("deleteme_deleteme.pnm","w"); % tempfile
[Mr Nr]=size(r);
if nargin==1
  fprintf(fd,"P5\n");
  fprintf(fd,"%d  %d\n",Nr,Mr);
  fprintf(fd,"255\n");
  % clip values beyond 255 to 255
  r=round(max(min(r,255),0));
  fwrite(fd,r',"uchar");
else%if
  [Mg Ng]=size(g);
  [Mb Nb]=size(b);
  if (Mr==Mg) & (Mr==Mb) & (Nr==Ng) & (Nr==Nb)
    M=Mr; N=Nr;  % all the same
    fprintf(fd,"P6\n")
    fprintf(fd,"%d  %d\n",N,M);
    fprintf(fd,"255\n")
    % clip values beyond 255 to 255
    r=round(max(min(r,255),0));
    g=round(max(min(g,255),0));
    b=round(max(min(b,255),0));
    r = reshape(r',1,M*N);
    g = reshape(g',1,M*N);
    b = reshape(b',1,M*N);
    fwrite(fd,[r;g;b],"uchar");
  else%if
    error("tvs.m: images must be same size")
  end%if
end%if
fclose(fd);
system("xv deleteme_deleteme.pnm &");





and here's a front end for it that emulates pv-wave's "tvscl" function:



% tvs.m scaled version of tv()
% inspired by pv-wave function tvscl
function tvs(r,g,b);
[Mr Nr]=size(r);
if nargin==1
  maxr=max(max(r));
  minr=min(min(r));
  r=round(255.0*(r-minr)/(maxr-minr));
  tv(r);
else%if
  maxr=max(max(r)); minr=min(min(r)); r=round(255.0*(r-minr)/(maxr-minr));
  maxg=max(max(g)); ming=min(min(g)); g=round(255.0*(g-ming)/(maxg-ming));
  maxb=max(max(b)); minb=min(min(b)); b=round(255.0*(b-minb)/(maxb-minb));
  tv(r,g,b);
end%if



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