MATLAB: Please how can i save the extracted feature in bmp format, i tried saving it but is not working

Question

here is the code

% Dir = 'C:\Users\Markama\Documents\MATLAB\Ahmad lema\Att faces\orl_faces\test\'; 
% % Read images from Images folder
% Imgs = dir(fullfile(Dir, '*.bmp'));
% for i=1:length(Imgs)
%   im = imread(fullfile(Dir, Imgs(i).name)); 
im= imread('test.bmp');
    rows=size(im,1);
    cols=size(im,2);
    t=5;
    %// Reordering vector - Essentially for getting binary strings
    reorder_vector = [8 7 4 1 2 3 6 9];
      %// For the upper and lower LTP patterns
      ltp_upper = zeros(size(im));
      ltp_lower = zeros(size(im));
      %// For each pixel in our image, ignoring the borders...
      for row = 2 : rows - 1
          for col = 2 : cols - 1
              cen = im(row,col); %// Get centre
              %// Get neighbourhood - cast to double for better precision
              pixels = double(im(row-1:row+1,col-1:col+1));
              %// Get ranges and determine LTP
              out_LTP = zeros(3, 3);
              low = cen - t;
              high = cen + t;
              out_LTP(pixels < low) = -1;
              out_LTP(pixels > high) = 1;
              out_LTP(pixels >= low & pixels <= high) = 0;
              %// Get upper and lower patterns
              upper = out_LTP;
              upper(upper == -1) = 0;
              upper = upper(reorder_vector);
              lower = out_LTP;
              lower(lower == 1) = 0;
              lower(lower == -1) = 1;
              lower = lower(reorder_vector);
              %// Convert to a binary character string, then use bin2dec
              %// to get the decimal representation
              upper_bitstring = char(48 + upper);
              ltp_upper(row,col) = bin2dec(upper_bitstring);
              lower_bitstring = char(48 + lower);
              ltp_lower(row,col) = bin2dec(lower_bitstring);
          end
      end
      figure
      imshow(ltp_upper);
      imwrite (ltp_upper, ltp_lower,'1.bmp');
% end

Answer 1

You can't save two images in one call. Do two separate calls:

imwrite(ltp_upper, '1.bmp');
imwrite(ltp_lower, '2.bmp');

Also, IMPORTANT, don't use "upper" and "lower" for variable names since those are the names of built-in functions.