contract-diff

Compare contract templates (Word/PDF) with scanned stamped contracts (PDF/images), list ALL differences, and generate a highlighted visualization showing where changes are.

When to Use

• User uploads a contract template AND a scanned signed contract
• User wants to know EVERY difference between template and signed version
• User needs detailed report showing additions, deletions, and modifications
• User needs visual highlighting of modified areas in the scanned contract

Workflow

Step 1: Extract Text from Both Files

For contract template (.docx): Use python-docx to extract all text.

For contract template (.pdf): Use PyMuPDF (fitz) to extract text.

For scanned contract (PDF or image): Use OCR with pytesseract to extract text with bounding boxes.

Step 2: Detailed Comparison

Split text into sentences/paragraphs and categorize:

1. Only in template - Content that was deleted
2. Only in scanned - Content that was added
3. Similar but different - Modified content (with similarity ratio)

Using difflib.SequenceMatcher with threshold:

• 85% similarity: treated as same

• 50-85% similarity: marked as modified
• \x3C 50% similarity: marked as added/deleted

Step 3: Generate Highlighted Image

For modified content:

• Find text position in OCR results
• Draw colored highlight box:
  • 🟡 Yellow = Modified content

Step 4: Generate Detailed Report

Output format:

# 合同比对详细报告

## 📋 文件信息
- **模板文件**: [filename]
- **盖章合同**: [filename]

## 📊 比对结果总览
- **风险等级**: 🟢低/🟡中/🔴高
- 🔴 删除内容: X 处
- 🟢 新增内容: X 处
- 🟡 修改内容: X 处

## 🔴 删除内容（模板 → 盖章合同）
1. [content...]
2. [content...]

## 🟢 新增内容（模板 → 盖章合同）
1. [content...]
2. [content...]

## 🟡 修改内容对比
| 模板内容 | 扫描件内容 | 相似度 |
|----------|------------|--------|
| ... | ... | 0.xx |

---
*⚠️ 注：比对结果基于 OCR 文字识别，可能存在误差。*

Usage

# 安装依赖
pip install python-docx PyMuPDF pillow pytesseract

# 运行比对（输出 Word 文档）
python scripts/compare.py contract_template.docx signed_contract.pdf

# 指定输出文件
python scripts/compare.py template.pdf scan.pdf -o report.docx

Dependencies

Required Python packages:

• python-docx - for .docx files
• PyMuPDF (fitz) - for PDF text extraction
• Pillow - image processing
• pytesseract - OCR
• Tesseract-OCR binary (system-level installation required)

Important Notes

1. OCR 准确性: 扫描件 OCR 可能存在误差，特别是手写或模糊文字
2. 高亮精度: 高亮依赖于 OCR 识别的坐标，可能有轻微偏移
3. 详细比对: 新版算法会列出所有差异，包括新增、删除、修改
4. 脱敏处理: 敏感信息用 *** 代替

Output Files

Windows Setup

1. Install Python 3.12+
2. Install Tesseract OCR: winget install tesseract-ocr.tesseract
3. Install Python packages:

   pip install python-docx PyMuPDF pillow pytesseract
   

Example

# Compare two contract files, output as Word document
python compare.py "合同模板.docx" "盖章合同.pdf" -o "详细比对报告.docx"

Output includes:

• All content only in template (deletions)
• All content only in scanned (additions)
• All similar but modified content with similarity scores