From octave-sources-request at bevo dot che dot wisc dot edu Sun Dec  1 20:29:15 2002
Subject: Contributes ppmread.m
From: matuda <0131277601 at jcom dot home dot ne dot jp>
To: bug-octave at bevo dot che dot wisc dot edu
Date: Sun, 1 Dec 2002 19:37:16 -0600

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Hello dear!

The "ppmread.m" function is for reading ppm foramt image files to 
have Octave's RGB matrixes.
I tested ppm and pgm files created with ImageMagick and Netpbm.
I wish this function is helpfull for all Octave users.

Namio MATUDA <matuda at film dot s dot dendai dot ac dot jp>
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## -*- texinfo -*-
##  at deftypefn {Function File} {[@var{r}, @var{g}, @var{b}] =} ppmread (@var{file})
## Load an image file stored in ppm and pgm format from the specified 
##  at var{file} dot 
##  at end deftypefn
##  at seealso{loadimage, saveimage, load, and save} 

## Author: Namio Matuda <matuda at film dot s dot dendai dot ac dot jp>
## Created: December 2002

function [R_ret, G_ret, B_ret] = ppmread (filename)

  if (nargin != 1)
    usage ("[r, g, b] = ppmread (filename)");
  elseif (! isstr (filename))
    error ("ppmread: expecting filename as a string");
  endif

  file = file_in_path (IMAGEPATH, filename);

  if (isempty (file))
    error ("ppmread: unable to find image file");
  endif

  ## The file is assumed to have variables img and map, or X and map.

  ip = fopen(file, 'rb');
  mg = fscanf(ip, "%s",1);
  iscom=fscanf(ip, "%s",1);
  if iscom(1) == '#'; c = 0; 
    while  c != 10 ; c=fread(ip, 1, 'uchar'); endwhile;
    %fread(ip, 1, 'uchar'); 
    wsize=str2num(fscanf(ip, "%s",1));
  else wsize=str2num(iscom);
  endif
  
  hsize=str2num(fscanf(ip, "%s",1));
  maxc = str2num(fscanf(ip, "%s",1));
 
  R=zeros(hsize,wsize);
  G=zeros(hsize,wsize);
  B=zeros(hsize,wsize);

  switch mg;

  case "P2" 
    switch maxc;
      case 65535;
        for jh = 1:hsize
          RGB=fscanf(ip, "%d", wsize)'/maxc;
          R(jh,:)=RGB(1:wsize);
          G(jh,:)=R(jh,:);
          B(jh,:)=R(jh,:);
        endfor
      case 255;
        fread(ip, 1, 'uchar');
        for jh = 1:hsize
          RGB=fscanf(ip, "%u", wsize)'/maxc;
          R(jh,:)=RGB(1:wsize);
          G(jh,:)=R(jh,:);
          B(jh,:)=R(jh,:);
        endfor
    endswitch

  case "P3"
    fread(ip, 1, 'uchar');
    switch maxc;
      case 65535;
        for jh = 1:hsize
          RGB = fscanf(ip, "%d", 3*wsize)'/maxc;
          R(jh,:)=RGB(1:3:3*wsize-2);
          G(jh,:)=RGB(2:3:3*wsize-1);
          B(jh,:)=RGB(3:3:3*wsize);
        endfor
      case 255;
        for jh = 1:hsize
          RGB = fscanf(ip, "%u", 3*wsize)'/maxc;
          R(jh,:)=RGB(1:3:3*wsize-2);
          G(jh,:)=RGB(2:3:3*wsize-1);
          B(jh,:)=RGB(3:3:3*wsize);
        endfor
      endswitch
 
  case "P5" 
    switch maxc;
      case 65535;
        for jh = 1:hsize
          RGB=fread(ip, wsize, 'uint')'/maxc;
          R(jh,:)=RGB(1:wsize);
          G(jh,:)=R(jh,:);
          B(jh,:)=R(jh,:);
        endfor
      case 255;
        fread(ip, 1, 'uchar');
        for jh = 1:hsize
          RGB=fread(ip, wsize, 'uchar')'/maxc;
          R(jh,:)=RGB(1:wsize);
          G(jh,:)=R(jh,:);
          B(jh,:)=R(jh,:);
        endfor
    endswitch
    
  case "P6"
    switch maxc;
      case 65535;
        for jh = 1:hsize
          RGB = fread(ip, 3*wsize, 'ushort')'/maxc;
          R(jh,:)=RGB(1:3:3*wsize-2);
          G(jh,:)=RGB(2:3:3*wsize-1);
          B(jh,:)=RGB(3:3:3*wsize);
        endfor
      case 255;
        fread(ip, 1, 'uchar');
        for jh = 1:hsize
          RGB = fread(ip, 3*wsize, 'uchar')'/maxc;
          R(jh,:)=RGB(1:3:3*wsize-2);
          G(jh,:)=RGB(2:3:3*wsize-1);
          B(jh,:)=RGB(3:3:3*wsize);
        endfor
    endswitch

  endswitch

  fclose(ip);
  R_ret=R; G_ret=G; B_ret=B;

endfunction


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