function vol2exp(input_file, sample, output_file_base)

%VOL2EXP writes input for the IRIS Explorer latin module.
%
% VOL2EXP( INPUT_FILE [, SAMPLE  [, OUTPUT_FILE_BASE]] )
%
% INPUT_FILE is the input .mnc or .img file.
%
% OUPUT_FILE_BASE: writes INPUT_FILE to OUPUT_FILE_BASE.exp. 
% Default is INPUT_FILE minus extension.
%
% SAMPLE is a 3 x 3 matrix whose rows are the start, step and stop
% indices, and whose columns are the x y and z directions. Default is 
% [1 1 d.dim(1); 1 1 d.dim(2); 1 1 d.dim(3)] i.e. all the data.

if nargin < 3
   sinf=size(input_file,2)
   if input_file(sinf) == 'z'
      output_file_base=input_file(1:(sinf-7))
   else
      output_file_base=input_file(1:(sinf-4)) 
   end
end

d=fmris_read_image(input_file);
if nargin < 2
    sample=[1 1 d.dim(1); 1 1 d.dim(2); 1 1 d.dim(3)]
end

% For .mnc files, emma flips the slices if the voxel sizes are <0, 
% so we have to flip the voxel sizes and origin:

ext=input_file((length(input_file)-2):length(input_file));
isanalyze= all(ext=='img')
if d.vox(1)<0 & ~isanalyze
    d.origin(1)=d.origin(1)+d.vox(1).*d.dim(1);
    d.vox(1)=-d.vox(1);
end
if d.vox(2)<0 & ~isanalyze
    d.origin(2)=d.origin(2)+d.vox(2).*d.dim(2);
    d.vox(2)=-d.vox(2);
end

x=sample(1,1):sample(1,2):sample(1,3);
y=sample(2,1):sample(2,2):sample(2,3);
z=sample(3,1):sample(3,2):sample(3,3);

sizes=[length(x) length(y) length(z)]
m=[min(x) min(y) min(z); max(x) max(y) max(z)];
bbox=m.*[d.vox; d.vox]+[d.origin; d.origin]

fid=fopen([output_file_base '.exp'],'w');
% first 3 are dimension sizes as 4-byte integers:
fwrite(fid,sizes,'int');
% next 6 are bounding box as 4-byte floats: 
fwrite(fid,bbox,'float');
% rest are the data as 4-byte floats:
fwrite(fid,d.data(x,y,z),'float');
fclose(fid)

return