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Clear TIFF core image if memory mapping was used for last load #8962

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Clear TIFF core image if memory mapping was used for last load #8962

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radarhere
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@radarhere radarhere commented May 21, 2025 •
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Resolves #8961

Using memory mapping to load one frame, and then not using it for the next frame, is causing a problem. This would be because memory mapping is replacing the core image.

Pillow/src/PIL/ImageFile.py

Lines 324 to 326 in 3c71559

self.im = Image.core.map_buffer(
self.map, self.size, decoder_name, offset, args
)

But TiffImagePlugin tries to keep using it afterwards.

Pillow/src/PIL/TiffImagePlugin.py

Lines 1214 to 1223 in 3c71559

def seek(self, frame: int) -> None:
"""Select a given frame as current image"""
if not self._seek_check(frame):
return
self._seek(frame)
if self._im is not None and (
self.im.size != self._tile_size or self.im.mode != self.mode
):
# The core image will no longer be used
self._im = None

@radarhere radarhere added the TIFF label May 21, 2025
@radarhere radarhere mentioned this pull request May 21, 2025
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@wiredfool
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Does it make sense to set the c level read-only flag on the image if it's memmapped, and then check if the image is read-only instead? Would the mmap also cause an issue if someone were to try to imagedraw on it?

@radarhere
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I've updated the commit to use the Python readonly flag.

ImageDraw should be fine, thanks to this code in ImageDraw.__init__.

Pillow/src/PIL/ImageDraw.py

Lines 78 to 79 in 3c71559

if im.readonly:
im._copy() # make it writeable

@wiredfool wiredfool mentioned this pull request May 23, 2025
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Successfully merging this pull request may close these issues.

Segfault when seeking to position 0 from any position in a TIFF image and reading the numpy array
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@radarhere @wiredfool