function MRI_overlay_histogram(mrifilename,figfilename,xlimits)
%MRI_overlay_histogram(mrifilename,figfilename[,xlimits])
%
%INPUTS:
% mrifilename = the name of the mri volume overlay
% figfilename = the filename of the png file to output
%               if empty, no figure will be saved
% xlimits = the limits on the x axis (optional)
%
% This function, given an MRI overlay file in any of the accepted
% formats (.nii, .mgz, etc) will output a histogram image
% showing the distribution of data values.
% Also, min,max,median and mean will be output.
%
% Note: you must source the freesurfer environment for this
% to work, because MRIread is called.

d=dir(mrifilename);
if isempty(d)
    disp('ERROR: mri file not found.');
    return;
end
[PATHSTR,NAME,EXT,VERSN] = fileparts(mrifilename);
fprintf('Reading %s ...',fullfile(pwd,[NAME EXT]));
mri = MRIread(mrifilename,0);
v1 = mri.vol(:);
v = v1(find(isfinite(v1)));
fprintf('Total voxels: %d. ',length(v1));
if length(v1) > length(v)
fprintf('%d infinite and %d Nan values excluded.\n',...
    length(find(isinf(v1))),length(find(isnan(v1))));
else
    fprintf('All voxels finite (a good thing).\n');
end
%close all;
%figure
hist(v,100);
if exist('xlimits') && ~isempty(xlimits)
    xlim(xlimits);
end

if exist('figfilename') && ~isempty(figfilename)
   exportfig(gcf, figfilename, 'format', 'png', 'color', 'cmyk', ...
     'height', 6, 'FontMode', 'fixed', 'FontSize', 12)
end
fprintf('Min...Max: %f ... %f\n',min(v),max(v));
fprintf('Mean...Median: %f ... %f \n',mean(v),median(v));