[Python] Why am I getting "I/O operation on closed file" with PILLOW 3.1.0?

I am attempting to convert a tiff file into a PDF using Pillow and PyPDF. I was able to get this to work using an earlier version of Pillow, although I cannot which version.

I recently upgraded to Pillow 3.1.0, and now I ran into issues. This is the previously working code.

import os
import traceback

from PIL import Image
from PyPDF2 import PdfFileReader, PdfFileMerger

to_merge = []

with Image.open('my_tif.tif') as img:
seeker = 0

while True:
try:
# temp file name for PDF
img_pdf = 'temp_{}.pdf'.format(seeker)

#seeks to next image with TIFF
img.seek(seeker)

# saves the image as a PDF
img.save(img_pdf)

seeker += 1
to_merge.append(img_pdf)

except Exception as err:
traceback.print_exc()
break

merger = PdfFileMerger()
for f in to_merge:
merger.append(PdfFileReader(f))
os.remove(f)
merger.write('merged.pdf')


Beforehand, it generated a PDF for each image within the tiff and then merged the PDFs together with no problem.

After I upgraded to Pillow 3.1.0 it loops through all of the images, but then throws a ValueError on the final image.

Traceback (most recent call last):
File "C:/Code/Python/tiff_to_pdf.py", line 16, in <module>
img.save(img_pdf)
File "C:\Python27\lib\site-packages\PIL\Image.py", line 1675, in save
save_handler(self, fp, filename)
File "C:\Python27\lib\site-packages\PIL\PdfImagePlugin.py", line 155, in _save
im.seek(pageNumber)
File "C:\Python27\lib\site-packages\PIL\TiffImagePlugin.py", line 930, in seek
self._seek(max(frame, 0)) # Questionable backwards compatibility.
File "C:\Python27\lib\site-packages\PIL\TiffImagePlugin.py", line 956, in _seek
self.fp.seek(self._frame_pos[frame])
ValueError: I/O operation on closed file


What would be the cause of the ValueError?

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