HTML with show layout bbox is not correctly overlayed

[tkaisermayer]

Bug

I was trying out docling CLI and used the export to HTML with layout overlay. Seems base pdf and overlay do not fit together.

I used only page 2 from https://arxiv.org/pdf/2408.09869v5.pdf
ExtractPage_code.pdf

The output looks like this (Google Chrome):

...

Steps to reproduce

docling --to html_split_page --show-layout --pipeline vlm --vlm-model granite_docling "ExtractPage_code.pdf"
...

Docling version

Docling version: 2.55.1
Docling Core version: 2.48.4
Docling IBM Models version: 3.9.1
Docling Parse version: 4.5.0
Python: cpython-311 (3.11.9)
Platform: Windows-10-10.0.22631-SP0
...

Python version

Python 3.11.9
...

[dosubot]

Hi @tkaisermayer! I'm Dosu and I’m helping the docling team.

This overlay misalignment is likely due to differences in coordinate systems between the extracted PDF layout and the HTML overlay rendering. Docling stores bounding boxes using the bottom-left origin (CoordOrigin.BOTTOMLEFT), which matches most PDF systems, but HTML/CSS overlays often expect a top-left origin. There are conversion methods in Docling for bounding box orientation, but these aren't exposed in the CLI or during export, so overlays can end up misaligned if the coordinate origins don't match. This is a known issue, especially for certain page orientations or when scaling/cropping isn't handled consistently in the export pipeline. There are ongoing discussions about exposing orientation options to users, but this feature isn't available yet. For now, you may need to manually adjust the overlay or check if the page orientation (portrait vs. landscape) is affecting the coordinate mapping. More details and related discussions can be found here and here.

To reply, just mention @dosu.

---

^{How did I do? Good | Irrelevant | Incorrect | Verbose | Hallucination | Report 🐛 | Other}