title: Extract only one file type with binwalk
body: <p>I have a very heavy file and with binwalk I have to extract only one file type (png) and obviously given the size of the file I can not extract all. <br>
  I tried to do <code>binwalk -D 'png image:png' [filename]</code> but continue to extract all files.
  How can I make binwalk extract only the files I want?</p>