SpectroscopyAnalysis/loadsxm.m at master · abhaykunayak/SpectroscopyAnalysis · GitHub

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function [header, data] = loadsxm(fn, varargin)
% loadsxm  Nanonis SXM file loader
%   [header, data] = loadsxm(fn, varargin) reads a Nanonis
%   SXM file fn.
%   Without a second argument, only the header is returned.
%   With a second argument n, the return value data contains
%   the n-th data set of the scan.
%   n is calculated 2*channel number + 0/1 depending on
%   whether forward of backward data should be loaded.

data=''; header='';

if exist(fn, 'file')
               fid = fopen(fn, 'r', 'ieee-be');    % open with big-endian
else
               fprintf('File does not exist.\n');
               return;
end

% check whether file is a Nanonis data file.
s1 = fgetl(fid);
if ~strcmp(s1, ':NANONIS_VERSION:')
               fprintf('File seems not to be a Nanonis file\n');
               return;
end
% get header
header.version = str2num(fgetl(fid));
read_tag = 1;

% read header data
% The header consists of key-value pairs. Usually the key is on one line, embedded in colons
% e.g. :SCAN_PIXELS:, the next line contains the value.
% Some special keys may have multi-line values (like :COMMENT:), in this case read value
% until next key is detected (line starts with a colon) and set read_tag to 0 (because key has
% been read already).
while 1
               if read_tag
                               s1 = strtrim(fgetl(fid));
               end
               s1 = s1(2:length(s1)-1);    % remove leading and trailing colon
               read_tag = 1;
               switch s1
               % strings:
               case {'SCANIT_TYPE', 'REC_DATE', 'REC_TIME', 'SCAN_FILE', 'SCAN_DIR'}
                               s2 = strtrim(fgetl(fid));
                               header.(lower(s1)) = s2;
               % comment:
               case 'COMMENT'
                               s_com = '';
                               s2 = strtrim(fgetl(fid));
                               while ~strncmp(s2, ':', 1)
                                              s_com = [s_com s2 char(13)];
                                              s2 = strtrim(fgetl(fid));
                               end
                               header.comment = s_com;
                               s1 = s2;
                               read_tag = 0;  % already read next key (tag)
               % Z-controller settings:
               case 'Z-CONTROLLER'
                               header.z_ctrl_tags = strtrim(fgetl(fid));
                               header.z_ctrl_values = strtrim(fgetl(fid));
               % numbers:
               case {'BIAS', 'REC_TEMP', 'ACQ_TIME', 'SCAN_ANGLE'}
                               s2 = fgetl(fid);
                               header.(lower(s1)) = str2num(s2);
               % array of two numbers:
               case {'SCAN_PIXELS', 'SCAN_TIME', 'SCAN_RANGE', 'SCAN_OFFSET'}
                               s2=fgetl(fid);
                               header.(lower(s1)) = sscanf(s2, '%f');
               % data info:
               case 'DATA_INFO'
                               s = '';
                               s2=strtrim(fgetl(fid));
                               while length(s2)>2
                                              s = sprintf('%s\n%s', s, s2);
                                              s2 = strtrim(fgetl(fid));
                               end
                               header.data_info = s;
               case 'SCANIT_END'
                               break;
    otherwise % treat as strings
                               s1 = regexprep(lower(s1), '[^a-z0-9_]', '_');
                               s_line = strtrim(fgetl(fid));
                               s2 = '';
                               while ~strncmp(s_line, ':', 1)
                                              s2 = [s2 s_line char(13)];
                                              s_line = strtrim(fgetl(fid));
                               end
                               header.(s1) = s2;
                               s1 = s_line;
                               read_tag = 0;  % already read next key (tag)
               end
end

% \1A\04 (hex) indicates beginning of binary data
s1 = [0 0];
while s1~=[26 4]
               s2 = fread(fid, 1, 'char');
               s1(1) = s1(2);
               s1(2) = s2;
end

% read the data if requested
if nargin > 1
               im_nr = varargin{1};
               size = prod(header.scan_pixels)*4;   % 4 Bytes per pixel
               fseek(fid, im_nr*size, 0);

               pix = header.scan_pixels;
               data = fread(fid, [pix(1) pix(2)], 'float');
               data = transpose(data);
end

fclose(fid);