Large BMP files crash (i.e. more than 2**32 pixels)

[nmz787]

I started asking on StackOverflow about my original problem, and the code is pasted over there:
https://stackoverflow.com/questions/59353721/python-pillow-opening-1-bit-depth-files-with-8-bits

but after moving to a larger machine (256 GB RAM) I moved on from the original issue and onto an Exception in the code.

Basically I'm trying to save a 59GigaPixel single-channel (1 bit depth) BMP file, which is yielding this error:

Traceback (most recent call last):
  File "stitch_bmps.py", line 75, in <module>
    blank.save("59GP.bmp", "BMP")
  File "/home/nmz787/.local/lib/python3.7/site-packages/PIL/Image.py", line 2084, in save
    save_handler(self, fp, filename)
  File "/home/nmz787/.local/lib/python3.7/site-packages/PIL/BmpImagePlugin.py", line 332, in _save
    + o32(offset)  # reserved
  File "/home/nmz787/.local/lib/python3.7/site-packages/PIL/_binary.py", line 91, in o32le
    return pack("<I", i)
struct.error: 'I' format requires 0 <= number <= 4294967295

Here's a small example to reproduce easily (requires at least 61GB of RAM, or RAM+swap):

from PIL import Image
a = Image.new("1", (247246, 247246))
a.save("blank_59GP.bmp", "BMP")

What are your OS, Python and Pillow versions?

• OS: Linux version 4.9.164-vs2.3.9.8-beng (root@ex64-jessie) (gcc version 4.9.2 (Debian 4.9.2-10+deb8u2) ) Merge pull request from @shuge #1 SMP Wed Mar 20 20:18:21 GMT 2019
• PIP: 18.1
• Python: 3.7.3

[nmz787]

Pillow Version: 6.2.1

[kkopachev]

Looks like BMP max filesize is limited to 4GiB. The second field in BMF file header is filesize in bytes, which is 4 bytes int, which can not exceed 2^32 (4GiB). Since your image is 1bpp image, with given dimensions image size would have to be 7,641,879,368 bytes, which exceeds 4 byte int capacity.

[nmz787]

Thanks for the clarification, can we get this notice added to the code during the save call, so it's absolutely clear what the problem is (user error).

[radarhere]

Thanks @kkopachev for figuring this one out.

I've created PR #4283 to throw a clearer error.