title: Compare Tif File Made from PDF pages
body: <p>I have a PDF File with about 500 pages with a lot of duplicates.
  Before I made PNG Thumbnails, then I made MD5-hashs to compare everything. That worked fine.
  Now I don't use png thumbnails anymore but tif-files because I have to use "tiffsep" to remove some spotcolors.
  If I compare the hashes of the tif-files or even the hashes of the png-files I made from the tif-files its completly different, even if it visually is the same.</p>
  
  <p>I tried to remove the datetimefield and the paging-information from the tiff-metadata but it is still the same.</p>
  
  <p>What can I do?
  Thats the code how the thumbnails are generated
      <code>inputpdf = PdfFileReader(path)
      count_pages = inputpdf.getNumPages()
      command = "gs -sDEVICE=tiffsep -dNoSeparationFiles -dLastPage="+str(count_pages)+" -sOutputFile="/home..../page_%d.tif"
      subprocess.Popen(command,shell=True,stdin....)</code></p>