Pymupdf4llm to_markdown crashes on some documents

[4rrw]

Description of the bug

Calling on to_markdown with this document crashes python.
output:

'example.py' terminated by signal SIGSEGV (Address boundary error)

Changing python versions does not help.
Changing pymupdf4llm version does not help.
Just loading pdf using pymupdf does work.

How to reproduce the bug

import pymupdf4llm

document_filepath = "documents/example-document.pdf"
pages = pymupdf4llm.to_markdown(
    document_filepath,
)

PyMuPDF version

1.25.5

Operating system

Linux

Python version

3.10

[JorjMcKie]

This is an upstream error (base library). The PDF is not built according to specifications:
The CropBox of all pages is not contained in the MediaBox - which is wrong. Example for page 0:

<<
  /Type /Page
  /Contents [ 16 0 R 17 0 R 18 0 R 19 0 R 26 0 R 27 0 R 49 0 R
      50 0 R ]
  /CropBox [ -21 -21 616.276 862.89 ]  # <== this is wrong: larger than MediaBox!
  /Group 61 0 R
  /MediaBox [ 0 0 595.28 841.89 ]
  /Parent 1 0 R
  /Resources <<
    /ColorSpace 5 0 R
    /ExtGState 6 0 R
    /Font 7 0 R
    /Pattern 8 0 R
    /ProcSet [ /PDF /ImageC /Text ]
    /Shading 9 0 R
    /XObject 10 0 R
  >>
  /Rotate 0
>>

However, the actually required internal correction is not done by MuPDF. The resulting incorrect value of page.rect is unexpected and leads to a storage violation when building certain internal Pixmaps.

For debugging purposes, I am attaching the sub-pdf with page 0 here:
page0.pdf

Link to MuPDF bug item: https://bugs.ghostscript.com/show_bug.cgi?id=708497

[JorjMcKie]

While we are dealing with this: the PDF can of course be repaired without major problems. Please let us know if you need that here.

[4rrw]

Thank you for the answer.

[JorjMcKie]

Discussing with the MuPDF team revealed that there is no MuPDF problem here, but a bug in PyMuPDF (not PyMuPDF4LLM).
Part of the extraction logic of PyMuPDF4LLM includes making some small Pixmaps for background color checking. Due to the wrong CropBox values in this PDF, some of these Pixmaps were empty which was not correctly checked, and ultimately resulting in storage violations you have experienced.
We are going to improve both, PyMuPDF and PyMuPDF4LLM to avoid this.

[JorjMcKie]

As an immediate fix, I have changed PyMuPDF4LLM to prevent this error from happening. Therefore I am going to transfer this issue to that repository's issue list.

[JorjMcKie]

Fixed with v0.0.22.