ZeroDivisionError in ImageStat #9104

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1. radarhere commented on Jul 22, 2025

   

   radarhere

   on Jul 22, 2025

   Last edited by radarhere

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   Hi. As you will have gathered from the traceback, self.count[i] is zero.

   count is the https://pillow.readthedocs.io/en/stable/reference/ImageStat.html#PIL.ImageStat.Stat.count

   Total number of pixels for each band in the image.

   The problem can be replicated quite simply by generating an image that is zero width by zero height.

   >>> from PIL import Image, ImageStat
   >>> im = Image.new("RGB", (0, 0))
   >>> stat = ImageStat.Stat(im)
   >>> stat.count
   [0, 0, 0]
   >>> stat.rms
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
     File "functools.py", line 993, in __get__
       val = self.func(instance)
     File "PIL/ImageStat.py", line 144, in rms
       return [math.sqrt(self.sum2[i] / self.count[i]) for i in self.bands]
     File "PIL/ImageStat.py", line 144, in <listcomp>
       return [math.sqrt(self.sum2[i] / self.count[i]) for i in self.bands]
   ZeroDivisionError: float division by zero

   I expect Pillow to validate before dividing by zero.

   Are you saying that Pillow should throw a custom error when ImageStat.Stat() is called with a zero by zero image? I would have thought a neater option would just be to return zero values as the rms.

   Also, you have said that you are using Pillow 10.4.0. I don't know what reason you have for not upgrading to the latest version, but be aware that if you wanted any fix we make for this, you would have to upgrade to at least Pillow 12.0.0, as that is the next release we have planned.
2. radarhere commented on Jul 23, 2025

   

   radarhere

   on Jul 23, 2025

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   I've created #9105 to return zero values.

   If you do find the image that triggered this, please let us know.
3. hugovk

   closed this as completedin #9105on Aug 27, 2025