title: HOG features for different image sizes and different aspect ratios
body: <p>I am using opencv and HOG features for image classification but one problem is my images are with different size and different aspect ratios(but it is guaranteed that all images under one class have the same aspect ratio).</p>
  
  <p>To have the same length of HOG feature, I can:</p>
  
  <ol>
  <li>Resize all images to the same size.</li>
  <li>Calculate the HOG parameters for each image so that they have same number of blocks and same number of cells. And thus they have the same length of HOG feature.</li>
  </ol>
  
  <p>So which is better?</p>