title: How to put my dataset in a .pkl file with many images whose size are different?
body: <p>I have many images and their size is not different. So, How to put my dataset in a .pkl file in the exact format and data structure used in “mnist.pkl.gz”?<br>
  it's also ok not to put in a pkl file if there are other good ways. What's the common way to read image data for a cnn net just like the way in the tutorial on deep learning web site. thanks everyone, this is the first time when I ask a question.  </p>