feat: add get_cell_image method to TableItem

[sriharan0804]

Summary

Closes #449

This PR adds a get_cell_image() helper method to TableItem to enable extraction of image crops corresponding to individual table cells.

Currently, TableCell objects may contain bounding box information, but there is no direct API for retrieving the image region represented by a cell. This change provides a convenient way to obtain cell-level image crops from the underlying page image.

Changes

• Added TableItem.get_cell_image()

• Reused the existing image cropping workflow used by DocItem.get_image()

• Added validation for:

  • missing cell bounding boxes
  • missing table provenance
  • missing page images

• Returns None when image extraction is not possible

Implementation Details

The method:

1. Retrieves the page associated with the table provenance.
2. Converts the cell bounding box to top-left origin coordinates.
3. Scales the bounding box to the rendered page image size.
4. Crops and returns the corresponding PIL image.

This follows the same coordinate conversion and image extraction logic already used elsewhere in the document model.

Testing

Added a unit test covering successful table cell image extraction.

Executed:

uv run pytest test/test_docling_doc.py -k "get_cell_image" -v

Result:

1 passed

Additional verification:

uv run pytest test/test_docling_doc.py -k "table" -v

Result:

10 passed

Linting:

uv run ruff check docling_core/types/doc/document.py test/test_docling_doc.py

Result:

All checks passed

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Thanks @sriharan0804, all your commits are properly signed off. 🎉

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[christymanthara]

@dolfim-ibm please review.

[sriharan0804]

hi @christymanthara , take a look at this PR