Saving binary tiff files with tiff_deflate compression fails under certain conditions

[eroux]

What did you do?

I have this file:

20210415185447038_0158.zip

(you'll have to unzip it to test, I zipped it so that I could upload it in this issue)

I'm running the following script:

from PIL import Image

img = Image.open("20210415185447038_0158.tiff")
# any of these operations make the final line work
#img = img.convert("L")
#img = img.rotate(180).rotate(180)
# removing the compression argument also makes it work
img.save("test.tiff", compression="tiff_deflate")

What did you expect to happen?

I expected the file to be saved

What actually happened?

I got

$ python3 convert_tiff.py 
_TIFFVSetField: toto2.tiff: Ignored tag "OldSubfileType" (not supported by libtiff).
Traceback (most recent call last):
  File "/home/admin/tmp/convert_tiff.py", line 8, in <module>
    img.save("toto2.tiff", compression="tiff_deflate")
  File "/home/admin/.local/lib/python3.9/site-packages/PIL/Image.py", line 2439, in save
    save_handler(self, fp, filename)
  File "/home/admin/.local/lib/python3.9/site-packages/PIL/TiffImagePlugin.py", line 1838, in _save
    e = Image._getencoder(im.mode, "libtiff", a, encoderconfig)
  File "/home/admin/.local/lib/python3.9/site-packages/PIL/Image.py", line 420, in _getencoder
    return encoder(mode, *args + extra)
RuntimeError: Error setting from dictionary

What are your OS, Python and Pillow versions?

• OS: Debian 5.10
• Python: 3.9.2
• Pillow: 10.2.0

The strange thing is that if I do anything with the image then saving works, or if I save it uncompressed it works too, it only fails when I save the untouched image.

[radarhere]

The problem is TIFF Tag 255, SubfileType.

Deleting the tag will cause the code to work.

from PIL import Image
img = Image.open("20210415185447038_0158.tiff")
del img.tag_v2[255]
img.save("test.tiff", compression="tiff_deflate")

When you're converting or rotating the image, you're copying it, and when it is copied, it loses the TIFF tags.

I've created #7893 to fix this by automatically deleting the tag when using compression.

[eroux]

thanks a lot!