GaussianBlur does not work with I;16

What did you do?

Attempted to use Image.filter(ImageFilter.BLUR) on an image of mode I or I;16

What did you expect to happen?

Image is blurred

What actually happened?

Code throws ValueError

What are your OS, Python and Pillow versions?

• OS: Windows 10 Home
• Python: 3.10.1
• Pillow: 9.2.0

>>> from tkinter import filedialog
>>> from PIL import Image, ImageFilter
>>> image1 = Image.open(filedialog.askopenfilename())
>>> image1
   <PIL.BmpImagePlugin.BmpImageFile image mode=RGB size=630x514 at 0x28B7051E9B0>
>>> image2 = image1.convert('I')
>>> image2
   <PIL.Image.Image image mode=I size=630x514 at 0x28B70A8E560>
>>> image1.filter(ImageFilter.BLUR).show()
>>> image2.filter(ImageFilter.BLUR).show()
   Traceback (most recent call last):
     File "<pyshell#56>", line 1, in <module>
       image2.filter(ImageFilter.BLUR).show()
     File "C:\Users\x\AppData\Local\Programs\Python\Python310\lib\site-packages\PIL\Image.py", line 1247, in filter
       return self._new(filter.filter(self.im))
     File "C:\Users\x\AppData\Local\Programs\Python\Python310\lib\site-packages\PIL\ImageFilter.py", line 32, in filter
       return image.filter(*self.filterargs)
   ValueError: image has wrong mode

The traceback points to PIL.Image.filter and PIL.ImageFilter.BLUR; start by reproducing the example with I and I;16 images and inspect where the wrong-mode error is raised. Done means the blur filter works for those modes without raising ValueError, with behavior checked against the reported expectation.