MATLAB: How to Save image Features in .mat file?

hogsave features

I am trying to extract facial features from image using HOG and trying to save them in .mat file, but when i run my code it saves the features of all images in one column. I want to save the features of each image in separate row.
Here is my CODE:
myFolder = 'folder'; % or whatever.
if ~isdir(myFolder)
  errorMessage = sprintf('Error: The following folder does not exist:\n%s', myFolder);
  uiwait(warndlg(errorMessage));
  return;
end
filePattern = fullfile(myFolder, '*.jpg');
matFiles = dir(filePattern);
for k = 1:length(matFiles)
  baseFileName = matFiles(k).name;
  img = fullfile(myFolder, baseFileName);
  fprintf(1, 'Now reading %s\n', img);
  storedStructure = imread(img);
  % Now do whatever you need to do with the structure you recalled.
  %figure    % New figure, do not specify the index
  %imshow(img);
  FaceDetect = vision.CascadeObjectDetector;
  FaceDetect.MergeThreshold = 7 ;
  BB = step(FaceDetect,storedStructure); %figure(2),imshow(img);
  for i = 1:size(BB,1)
     rectangle('Position',BB(i,:),'LineWidth',3,'LineStyle','- ','EdgeColor','r');
  end
  % figure
    for i = 1:size(BB,1)
      J= imcrop(storedStructure,BB(i,:));
      %subplot(6,6,i);
      figure
      imshow(J);
      % Create a folder with the base file name
      [~, baseFileNameNoExt, ~] = fileparts(baseFileName);
      outputFolder = fullfile(myFolder, baseFileNameNoExt);
      if ~exist(outputFolder, 'dir')
          mkdir(outputFolder);
          fprintf('Created folder : %s\n', outputFolder);
      end
      % Prepare output filename
      outputFileName = fullfile(outputFolder, baseFileName);
      % Write file to that folder
      imwrite(J, outputFileName);
      fprintf('    Copied %s to the folder called %s.\n', baseFileName, outputFolder);
    end
  end
  J
  HOG(J)
  X=HOG(J)
  save('features.mat','J');

Best Answer

In your code, the matrix you want to save is X, not J. Also, you are also calculating HOG feature for the last image. To calculate for all images and save them write your code as follows.
  • Before the start of first for loop add the following line
X = [];
  • At the end of inner for loop add the following line, like this
fprintf('    Copied %s to the folder called %s.\n', baseFileName, outputFolder); % line from your code
X{k, i} = HOG(J);
Each row in X represents HOG feature for one complete image. Each element in the row represents HOG features for one bounding box.
Then save the features like this
save('features.mat', 'X');
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