seek of closed file #1630
Description
I wanted to calculate a histogram of a multi-page TIFF file.
im = Image.open( fn )
colors = im.getcolors( im.width * im.height )
if args.hist:
for cnt, col in colors:
allcolors[ col ] += cnt
for iz in range( 1, im.n_frames ):
im.seek( iz )
colors = im.getcolors( im.width * im.height )
for cnt, col in colors:
allcolors[ col ] += cntThe above code would fail on the seek, with "seek of closed file" error. I tried first to add the extra open operation below just before the seek. It helped some, but not in every case.
im = Image.open( fn )
colors = im.getcolors( im.width * im.height )
if args.hist:
for cnt, col in colors:
allcolors[ col ] += cnt
for iz in range( 1, im.n_frames ):
im = Image.open( fn ) # does getcolors implicitly close????
# without the open, get "seek of closed
# file" error on line below.
im.seek( iz )
colors = im.getcolors( im.width * im.height )
for cnt, col in colors:
allcolors[ col ] += cntRandomly (or maybe experience based) guessing, I then tried hoisting the reference to n_frames out of the loop, as below. That seemed to make it reliable across a number of test cases that failed otherwise.
im = Image.open( fn )
imgcnt = im.n_frames
colors = im.getcolors( im.width * im.height )
if args.hist:
for cnt, col in colors:
allcolors[ col ] += cnt
for iz in range( 1, imgcnt ):
im = Image.open( fn ) # does getcolors implicitly close????
# without the open, get "seek of closed
# file" error on line below.
im.seek( iz )
colors = im.getcolors( im.width * im.height )
for cnt, col in colors:
allcolors[ col ] += cntWith this solution in hand, I tried removing the extra open inside the loop, but some failures recurred when I did so. So this last code is my "production solution" for now, but it is not at all clear why the initial code attempt at the top produces errors.
Pillow 3.0.0, Python 3.5.0, Windows 10.