Extraction of title from "section header" pages

[christianabbet]

Close #98

Description

In this PR we include a title estimation for pages that are labeled as section headers. The ground truth in data/gt_single_pages.json is updated with title entries. To extract the title GT, we used the Pixtral model and a predefined prompt. The Pixtral interface was refactored so that it can be used in the future for other tasks. For title detection we send the image along with the extracted text. Pixtral seems to have poor OCR capability.

Moreover, we started some refactoring of the evaluation process. We opened a new issue for future cleanup (#103)

Performance

The title is estimated based on multiple criteria and achieves 29.05% F1-score. For each criterion, the cumulative score is indicated.

• Font size: Titles are more likely to have a larger font (18.99%)
• Horizontality: The title should begin in the left half of the page (20.11%)
• Verticality: The title should begin within the top 75% of the page vertically (23.46%)
• Length: The title should be at least 5 characters long (24.58%)
• Alpha: The title should consist mostly of alphabetic characters, with few numbers (25.70%)
• Highness: The title is more likely to appear near the top of the page (29.05%)

API response

// API V2
{
  "has_finished": true,
  "data": {
    "filename": "35016.pdf",
    "page_count": 12,
    "languages": [
      "de"
    ],
    "entities": [
      {
        "classification": "title_page",
        "language": "de",
        "page_start": 1,
        "page_end": 1,
        "title": null
      },
      {
        "classification": "text",
        "language": "de",
        "page_start": 2,
        "page_end": 5,
        "title": "Boden Wasser Luft"
      },
      {
        "classification": "map",
        "language": "de",
        "page_start": 6,
        "page_end": 6,
        "title": null
      },
      {
        "classification": "boreprofile",
        "language": "de",
        "page_start": 7,
        "page_end": 7,
        "title": "RB 1"
      },
      {
        "classification": "boreprofile",
        "language": "de",
        "page_start": 8,
        "page_end": 8,
        "title": "RB 10"
      },
      {
        "classification": "diagram",
        "language": "de",
        "page_start": 9,
        "page_end": 12,
        "title": null
      }
    ]
  }
}

// API V1
{
  "has_finished": true,
  "data": [
    {
      "filename": "35016.pdf",
      "metadata": {
        "page_count": 12,
        "languages": [
          "de"
        ]
      },
      "pages": [
        {
          "predicted_class": "TitlePage",
          "page_number": 1,
          "page_metadata": {
            "language": "de",
            "is_frontpage": true
          }
        },
        {
          "predicted_class": "Text",
          "page_number": 2,
          "page_metadata": {
            "language": "de",
            "is_frontpage": false
          }
        },
        {
          "predicted_class": "Text",
          "page_number": 3,
          "page_metadata": {
            "language": "de",
            "is_frontpage": false
          }
        },
        {
          "predicted_class": "Text",
          "page_number": 4,
          "page_metadata": {
            "language": "de",
            "is_frontpage": false
          }
        },
        {
          "predicted_class": "Text",
          "page_number": 5,
          "page_metadata": {
            "language": "de",
            "is_frontpage": false
          }
        },
        {
          "predicted_class": "Map",
          "page_number": 6,
          "page_metadata": {
            "language": "de",
            "is_frontpage": false
          }
        },
        {
          "predicted_class": "Boreprofile",
          "page_number": 7,
          "page_metadata": {
            "language": "de",
            "is_frontpage": false
          }
        },
        {
          "predicted_class": "Boreprofile",
          "page_number": 8,
          "page_metadata": {
            "language": "de",
            "is_frontpage": false
          }
        },
        {
          "predicted_class": "Diagram",
          "page_number": 9,
          "page_metadata": {
            "language": "de",
            "is_frontpage": false
          }
        },
        {
          "predicted_class": "Diagram",
          "page_number": 10,
          "page_metadata": {
            "language": "de",
            "is_frontpage": false
          }
        },
        {
          "predicted_class": "Diagram",
          "page_number": 11,
          "page_metadata": {
            "language": "de",
            "is_frontpage": false
          }
        },
        {
          "predicted_class": "Diagram",
          "page_number": 12,
          "page_metadata": {
            "language": "de",
            "is_frontpage": false
          }
        }
      ]
    }
  ]
}