function [X,map]=loadbmp(bmpfile)
# LOADBMP  Load Microsoft Windows 3.x .BMP format image files.
#
#          [X,map]=LOADBMP(bmpfile) loads a .BMP format file specified by
#          "bmpfile", returning the image data in variable "X" and the
#          colormap in variable "map". The .BMP extension in the filename
#          is optional.
#
#          Note: LOADBMP currently supports only uncompressed .BMP files
#                with at most 256 colors.
#
#          See also SAVEBMP.

#          Copyright (c) 1993 by
#          
#          Ralph Sucher
#          Dept. of Communications Engineering
#          Technical University of Vienna
#          Gusshausstrasse 25/389
#          A-1040 Vienna
#          AUSTRIA
#          
#          Phone: +431-58801/3518
#          Fax:   +431-5870583
#          Email: address@hidden

if nargin~=1
   error('LOADBMP takes one argument, which is the name of the .BMP file.');
end

if length(findstr(bmpfile,'.'))==0
   bmpfile=[bmpfile,'.bmp'];
end

fid=fopen(setstr(bmpfile),'r','ieee-le');

if fid==-1
   error('Can''t open .BMP file for input!');
end

# ------------------------------- BMP HEADER -------------------------------

# read file identifier

bfType=fread(fid,2,'uchar')';
if !strcmp(setstr(bfType),'BM')
   fclose(fid);
   error('Not a valid .BMP file!');
end

# read file length (bytes)
status=fseek(fid,0,SEEK_END);
bfSize=ftell(fid);
status=fseek(fid,6,SEEK_SET);

# read bytes reserved for later extensions
dummy=fread(fid,1,'long');

# read offset from beginning of file to first data byte
bfOffs=fread(fid,1,'long');

# ----------------------------- BMP INFO-BLOCK -----------------------------

# *** bitmap information header ***

# read length of bitmap information header
biSize=fread(fid,1,'long');

# read width of bitmap
biWidth=fread(fid,1,'long');

# read height of bitmap
biHeight=fread(fid,1,'long');

# read number of color planes
biPlanes=fread(fid,1,'ushort');

# read number of bits per pixel
biBitCnt=fread(fid,1,'ushort');
nCol=2^biBitCnt;

# read type of data compression
biCompr=fread(fid,1,'long');
if biCompr~=0
   fclose(fid);
   error('LOADBMP currently supports only uncompressed .BMP files!');
end

# read size of compressed image
biSizeIm=fread(fid,1,'long');

# read horizontal resolution (pixels/meter)
biXPelsPerMeter=fread(fid,1,'long');

# read vertical resolution (pixels/meter)
biYPelsPerMeter=fread(fid,1,'long');

# read number of used colors
biClrUsed=fread(fid,1,'long');

# read number of important colors
biClrImportant=fread(fid,1,'long');

# *** colormap ***

MapLength=(bfOffs-54)/4;

# read colormap
map=zeros(4,MapLength);
map=fread(fid,[4 MapLength],'uchar');
map=map(3:-1:1,:)'/255;

# ------------------------------ BITMAP DATA -------------------------------

ndata=bfSize-bfOffs;
Width=(ndata*8/biBitCnt)/biHeight;
X=zeros(1,Width*biHeight);
Xsize=Width*biHeight;

data=fread(fid,ndata,'uchar');
fclose(fid);

if biBitCnt==1
   x=zeros(1,ndata);
   for i=1:8
       X(i:8:Xsize)=fix((data'-x)/2^(8-i));
       x=x+X(i:8:Xsize)*2^(8-i);
   end
elseif biBitCnt==4
   X(1:2:Xsize)=fix(data/16);
   X(2:2:Xsize)=round(data'-X(1:2:Xsize)*16);
elseif biBitCnt==8
   X=data;
elseif biBitCnt==24
   error('LOADBMP supports only images with at most 256 colors.');
else
   error('This is not a valid .BMP file!');
end

X=reshape(X,biWidth,biHeight);
X=X(1:biWidth,biHeight:-1:1)'+1;
endfunction