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A Comprehensive Toolkit for High-Quality PDF Content Extraction

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Overview

PDF documents contain a wealth of knowledge, yet extracting high-quality content from PDFs is not an easy task. To address this, we have broken down the task of PDF content extraction into several components:

  • Layout Detection: Using the LayoutLMv3 model for region detection, such as images, tables, titles, text, etc.;
  • Formula Detection: Using YOLOv8 for detecting formulas, including inline formulas and isolated formulas;
  • Formula Recognition: Using UniMERNet for formula recognition;
  • Table Recognition: Using StructEqTable for table recognition;
  • Optical Character Recognition: Using PaddleOCR for text recognition;

Note: Due to the diversity of document types, existing open-source layout and formula detection models struggle with diverse PDF documents. Therefore, we have collected diverse data for annotation and training to achieve precise detection effects on various types of documents. For details, refer to the sections on Layout Detection and Formula Detection. For formula recognition, the UniMERNet method rivals commercial software in quality across various types of formulas. For OCR, we use PaddleOCR, which performs well for both Chinese and English.

The PDF content extraction framework is illustrated below:

PDF-Extract-Kit Output Format
{
    "layout_dets": [    # Elements on the page
        {
            "category_id": 0, # Category ID, 0~9, 13~15
            "poly": [
                136.0, # Coordinates are in image format, need to convert back to PDF coordinates, order is top-left, top-right, bottom-right, bottom-left x,y coordinates
                781.0,
                340.0,
                781.0,
                340.0,
                806.0,
                136.0,
                806.0
            ],
            "score": 0.69,   # Confidence score
            "latex": ''      # Formula recognition result, only categories 13, 14 have content, others are empty, additionally 15 is the OCR result, this key will be replaced with text
        },
        ...
    ],
    "page_info": {         # Page information: resolution size when extracting bounding boxes, alignment can be based on this information if scaling is involved
        "page_no": 0,      # Page number
        "height": 1684,    # Page height
        "width": 1200      # Page width
    }
}

The types included in category_id are as follows:

{0: 'title',              # Title
 1: 'plain text',         # Text
 2: 'abandon',            # Includes headers, footers, page numbers, and page annotations
 3: 'figure',             # Image
 4: 'figure_caption',     # Image caption
 5: 'table',              # Table
 6: 'table_caption',      # Table caption
 7: 'table_footnote',     # Table footnote
 8: 'isolate_formula',    # Display formula (this is a layout display formula, lower priority than 14)
 9: 'formula_caption',    # Display formula label

 13: 'inline_formula',    # Inline formula
 14: 'isolated_formula',  # Display formula
 15: 'ocr_text'}          # OCR result

News and Update

  • 2024.08.01 🎉🎉🎉 Added the StructEqTable module for table content extraction. Welcome to use it!
  • 2024.07.01 🎉🎉🎉 We released PDF-Extract-Kit, a comprehensive toolkit for high-quality PDF content extraction, including layout detection, formula detection, formula recognition, and OCR.

Visualization of Results

By annotating a variety of PDF documents, we have trained robust models for layout detection and formula detection. Our pipeline achieves accurate extraction results on diverse types of PDF documents such as academic papers, textbooks, research reports, and financial statements, and is highly robust even in cases of scanned blurriness or watermarks.

Evaluation Metrics

Existing open-source models are often trained on data from Arxiv papers and fall short when facing diverse PDF documents. In contrast, our models, trained on diverse data, are capable of adapting to various document types for extraction.

The introduction of Validation process can be seen here.

Layout Detection

We have compared our model with existing open-source layout detection models, including DocXchain, Surya, and two models from 360LayoutAnalysis. The model present as LayoutLMv3-SFT in the table refers to the checkpoint we further trained with our SFT data on LayoutLMv3-base-chinese pre-trained model. The validation set for academic papers consists of 402 pages, while the textbook validation set is composed of 587 pages from various sources of textbooks.

Model Academic papers val Textbook val
mAP AP50 AR50 mAP AP50 AR50
DocXchain 52.8 69.5 77.3 34.9 50.1 63.5
Surya 24.2 39.4 66.1 13.9 23.3 49.9
360LayoutAnalysis-Paper 37.7 53.6 59.8 20.7 31.3 43.6
360LayoutAnalysis-Report 35.1 46.9 55.9 25.4 33.7 45.1
LayoutLMv3-SFT 77.6 93.3 95.5 67.9 82.7 87.9

Formula Detection

We have compared our model with the open-source formula detection model Pix2Text-MFD. Additionally, the YOLOv8-Trained is the weight obtained after we performed training on the basis of the YOLOv8l model. The paper's validation set is composed of 255 academic paper pages, and the multi-source validation set consists of 789 pages from various sources, including textbooks and books.

Model Academic papers val Multi-source val
AP50 AR50 AP50 AR50
Pix2Text-MFD 60.1 64.6 58.9 62.8
YOLOv8-Trained 87.7 89.9 82.4 87.3

Formula Recognition

BLEU

The formula recognition we used is based on the weights downloaded from UniMERNet, without any further SFT training, and the accuracy validation results can be obtained on its GitHub page.

Table Recognition

StructEqTable

The table recognition we used is based on the weights downloaded from StructEqTable, a solution that converts images of Table into LaTeX. Compared to the table recognition capability of PP-StructureV2, StructEqTable demonstrates stronger recognition performance, delivering good results even with complex tables, which may currently be best suited for data within research papers. There is also significant room for improvement in terms of speed, and we are continuously iterating and optimizing. Within a week, we will update the table recognition capability to MinerU.

Installation Guide(Linux)

conda create -n pipeline python=3.10

pip install -r requirements.txt

pip install https://github.com/opendatalab/PDF-Extract-Kit/raw/main/assets/whl/detectron2-0.6-cp310-cp310-linux_x86_64.whl

After installation, you may also encounter errors where torch cannot be invoked. First, uninstall the following library and then reinstall cuda12 and cudnn.

pip uninstall nvidia-cusparse-cu12

Refer to Model Download to download the required model weights.

Running on Windows

If you intend to run this project on Windows, please refer to Using PDF-Extract-Kit on Windows.

Running on macOS

If you intend to run this project on macOS, please refer to Using PDF-Extract-Kit on macOS.

Running in Google Colab

If you intend to experience this project on Google Colab, please Open In Colab

Run Extraction Script

python pdf_extract.py --pdf assets/examples/example.pdf

Parameter explanations:

  • --pdf: PDF file to be processed; if a folder is passed, all PDF files in the folder will be processed.
  • --output: Path where the results are saved, default is "output".
  • --vis: Whether to visualize the results; if yes, detection results including bounding boxes and categories will be visualized.
  • --render: Whether to render the recognized results, including LaTeX code for formulas and plain text, which will be rendered and placed in the detection boxes. Note: This process is very time-consuming, and also requires prior installation of xelatex and imagemagic.
  • --batch-size: Batch size for dataloader. Larger batch sizes are recommended, but smaller sizes require less GPU memory. Default is 128.

This project is dedicated to using models for high-quality content extraction from documents on diversity. It does not involve reassembling the extracted content into new documents, such as converting PDFs to Markdown. For those needs, please refer to our other GitHub project: MinerU

TODO List

  • Table Parsing: Develop a feature to convert table images into corresponding LaTeX/Markdown format source code.
  • Chemical Equation Detection: Implement automatic detection of chemical equations.
  • Chemical Equation/Diagram Recognition: Develop a model to recognize and parse chemical equations and diagrams.
  • Reading Order Sorting Model: Build a model to determine the correct reading order of text in documents.

PDF-Extract-Kit aims to provide high-quality PDF extraction capabilities. We encourage the community to propose specific and valuable requirements and welcome everyone to participate in continuously improving the PDF-Extract-Kit tool to advance scientific research and industrial development.

License

The project is released under the AGPL-3.0 license.

As this project incorporates YOLO code and PyMuPDF for file processing, both of which are licensed under AGPL-3.0, the entire repository adheres to the AGPL-3.0 license to ensure compliance with the licensing requirements of these dependencies.

Acknowledgement

Citation

If you find our models / code / papers useful in your research, please consider giving ⭐ and citations 📝, thx :)

@article{wang2024mineru,
  title={MinerU: An Open-Source Solution for Precise Document Content Extraction},
  author={Wang, Bin and Xu, Chao and Zhao, Xiaomeng and Ouyang, Linke and Wu, Fan and Zhao, Zhiyuan and Xu, Rui and Liu, Kaiwen and Qu, Yuan and Shang, Fukai and others},
  journal={arXiv preprint arXiv:2409.18839},
  year={2024}
}

@misc{wang2024unimernet,
      title={UniMERNet: A Universal Network for Real-World Mathematical Expression Recognition}, 
      author={Bin Wang and Zhuangcheng Gu and Chao Xu and Bo Zhang and Botian Shi and Conghui He},
      year={2024},
      eprint={2404.15254},
      archivePrefix={arXiv},
      primaryClass={cs.CV}
}
@article{he2024opendatalab,
  title={Opendatalab: Empowering general artificial intelligence with open datasets},
  author={He, Conghui and Li, Wei and Jin, Zhenjiang and Xu, Chao and Wang, Bin and Lin, Dahua},
  journal={arXiv preprint arXiv:2407.13773},
  year={2024}
}

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