## Copyright (C) 1996 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.

## Load an image file.
##
## [img, map] = loadimage (img_file) 
## loads an image and its associated color map from file img_file, 
## which must be in octave's image format.
##
## [img, map] = loadimage (img_file, "img") 
## is the same as loadimage (img_file).
##
## [r, g, b]  = loadimage (img_file, "ppm") 
## loads an image from file img_file, 
## which must be in color ppm format (ascii or binary).
##
## [img, map]  = loadimage (img_file, "ppm") 
## loads an image from file img_file, 
## which may be in any ppm format (ascii or binary).
## If the image is in color (ppm, not pgm or pbm), 
## rgb2ind() is used to convert it to an indexed image.
##
## if no output arguments are specified, the image is displayed
##
## SEE ALSO: saveimage, load, save

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

## Updated Nov 1999 to include ppm,pgm.pbm image formats by 
## Clif Kussmaul <kussmaul at cs dot moravian dot edu>
## and Tricia Salomonsen <salomonT at cs dot moravian dot edu>.

## Updated April 2005 fix some obsolete syntax for Octave 2.1 by
## En-ran Zhou <zhouer at gmail dot com>

function [varargout] = loadimage2 (filename, img_form)
  
  ## process arguments
   
  if (nargin < 1 || nargin > 2)
    usage ("[img, map] = loadimage (filename, [format])");
  endif
  
  if (! isstr (filename))
    error ("loadimage: file name must be a string");
  endif

  if (nargin < 2)
    img_form = "img";
  endif
  
  ########################################
  ## load image in octave's image format
  
  if (strcmp (img_form, "img"))
    ## file is in octave's image format, 
    ## and is assumed to have variables img and map, or X and map.
    
    file = file_in_path (IMAGEPATH, filename);

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

    eval (['load ', file]);

    if (exist ("img"))
      img_retval = img;
    elseif (exist ("X"))
      img_retval = X;
    else
      error ("loadimage: invalid image file found");
    endif

    if (exist ("map"))
      map_retval = map;
    else
      error ("loadimage: invalid image file found");
    endif
    
    if (nargout == 0) 
    	imshow(img_retval, map_retval);
    else
	varargout{1} = img_retval;
	varargout{2} = map_retval;
    endif
    ## end of img format


  ########################################
  ## load image in PBM/PGM/PPM image format
  
  elseif (strcmp (img_form, "ppm") || 
          strcmp (img_form, "pgm") ||
	  strcmp (img_form, "pbm")   )
        
    ## check magic number
    fp = fopen(filename,"rt");
    [magic, count] = fscanf(fp,"%s", "C") ;

    if (magic(1) != "P")
       error ("loadimage: invalid image file (bad magic number)");
    endif
    
    ## read 2 values (W,H) for pbm, 3 (W,H,M) for pgm or ppm
    if (magic(2) == "1" || magic(2) == "4")
      dneed = 2;
    else
      dneed = 3;
    endif
    while (dneed > 0)
      ## skip blank lines and comment lines
      while (1)
	data = fgetl(fp);
	if (length(data) > 0 && ! strcmp(data(1),"#")) break; endif
      endwhile
      ## try to read values
      [dvals, dcnt] = sscanf(data, "%d", dneed);
      if (dneed >= 3 && dneed - dcnt < 3)   dsize(3) = dvals(dneed - 2); endif
      if (dneed >= 2 && dneed - dcnt < 2)   dsize(2) = dvals(dneed - 1); endif
      if (dneed >= 1 && dneed - dcnt < 1)   dsize(1) = dvals(dneed - 0); endif
      dneed = dneed - dcnt;
    endwhile
    
    if     (magic(2) == "1" || magic(2) == "4")
      # read binary PBM in ascii ("1") or binary ("4") and transpose
      if (magic(2) == "1")
	data = fscanf(fp, "%d", [     dsize(2)    dsize(1)]         )';
      else
	idata = fread(fp,       [ceil(dsize(2)/8) dsize(1)], "uchar")';
	## unpack bits from bytes
	data  = zeros(dsize(1),dsize(2));
	for i=8:-1:1
          data(:,i:8:size(data,2))  =   rem(idata,  2); 
	  idata     	    	    = floor(idata / 2);
	endfor
      endif
      
      # would like to make 2-entry colormap, but imshow crashes in saveimage.m
      data = (!data) * 255;
      map = gray(256);
      if (nargout == 0)
	imshow(data, map);
      else
	varargout{1} = data;
	varargout{2} = map;
      endif
      
    elseif (magic(2) == "2" || magic(2) == "5")
      ## read greyscale PGM in ascii ("2") or binary ("5") and transpose
      if (magic(2) == "2")
	data = fscanf(fp, "%d", [dsize(3)   dsize(2)]         )';  
      else
        data = fread( fp,       [dsize(3)   dsize(2)], "uchar")';
      endif
      
      map = gray(dsize(1));
      if (nargout == 0)
        imshow(data, map);
      else
	varargout{1} = data;
	varargout{2} = map;
      endif
      
    elseif (magic(2) == "3" || magic(2) == "6")
      ## read color PPM in ascii ("3") or binary ("6")
      if (magic(2) == "3")
        data = fscanf(fp, "%d", [dsize(3)*3 dsize(2)]         );
      else 
        data = fread( fp,       [dsize(3)*3 dsize(2)], "uchar");
      endif
        
      # extract R,G,B values between 0 and 1
      data = data / dsize(1);
      r = data(1:3:size(data,1),:)';
      g = data(2:3:size(data,1),:)';
      b = data(3:3:size(data,1),:)';

      if (nargout == 0)
        imshow(r,g,b);
      elseif (nargout < 3)
	[img_retval, map_retval] = rgb2ind(r, g, b);
	varargout{1} = img_retval;
	varargout{2} = map_retval;
      elseif (nargout == 3)
	varargout{1} = r;
	varargout{2} = g;
	varargout{3} = b;

      endif

    else
    	error("loadimage: invalid image file (bad magic number)");
    endif
    
    fclose(fp);
    ## end of ppm/pgm/pbm format
	
  else
    error ("loadimage: image format not supported.");
  endif

endfunction