% ---------------------------------------------------------------------------
% Function grload()
%    -- Xenios Papademetris papad@noodle.med.yale.edu 5th Sep 1995
%
%    -- used to load images stored in the simple format (.grl) used for the
%    -- EE445a course, this has an unsigned short magic number (29571)
%    -- and the width and height of the image in 4-byte integers
%    -- followed by the actual data in unsigned char format
%    -- check for zero image lhs 2/2000
%    -- handles swapping lhs 2/2000
%    -- really handles swapping 1/2001
% ---------------------------------------------------------------------------

function outimage=grload(filename)

% ---------------------------------------------------------------------------
% Step 1 -- Check for right number of parameters
%        -- and check for valid filename
% ---------------------------------------------------------------------------

if nargin ~= 1
  error('Requires one input argument eg grload(filename)');
elseif nargin == 1 & isstr(filename)
  if (isempty(findstr(filename,'.'))==1)
        filename=[filename,'.grl'];
  end
end

% ---------------------------------------------------------------------------
% Step 2 -- Open filename
%        -- Check for valid file
% ---------------------------------------------------------------------------

handle=fopen(filename,'r');

if handle == -1       
      ff=['grload::cannot open file ' , filename];
        error (ff);
end

magic=fread(handle,1,'ushort');

if (magic~=29571 & magic ~=33651)
	ff=['grload::file ' , filename,' is not a grl file'];
	error (ff);
end

% ---------------------------------------------------------------------------
% Step 3 -- Read width and height
% ---------------------------------------------------------------------------

width1=fread(handle,1,'uchar');
width2=fread(handle,1,'uchar');
width3=fread(handle,1,'uchar');
width4=fread(handle,1,'uchar');

width = width4 + width3*256 + width2*256*256 + width1*256*256*256;
if (width>4096)
 width = width1 + width2*256 + width3*256*256 + width4*256*256*256;
end

height1=fread(handle,1,'uchar');
height2=fread(handle,1,'uchar');
height3=fread(handle,1,'uchar');
height4=fread(handle,1,'uchar');

height = height4 + height3*256 + height2*256*256 + height1*256*256*256;
if (height>4096)
  height = height1 + height3*256 + height3*256*256 + height4*256*256*256;
end 

disp('image size:');
disp([width,height]);

% ---------------------------------------------------------------------------
% Step 4 -- Read actual Image
% ---------------------------------------------------------------------------

outimage=fread(handle,[height,width],'uchar');
imax = max(max(outimage));
if imax ~= 0  
    outimage=outimage'/imax;
else
  disp('Zero image');
end

% ---------------------------------------------------------------------------
% Step 5 -- Close file
% ---------------------------------------------------------------------------

fclose(handle);

% ---------------------------------------------------------------------------