pdf-contract-redactor

# PDF Contract Redactor

Redact sensitive values from scanned PDF contracts while preserving field names.

## What It Does

1. **OCR Recognition**: Uses Alibaba Cloud OCR to extract text and positions from scanned PDFs
2. **Field-Value Matching**: Finds field names (e.g., "合同金额") and their corresponding values (e.g., "45640元")
3. **Selective Redaction**: Covers only the values with black boxes, keeping field names readable

## Workflow

### Step 1: PDF to Images
Convert PDF pages to high-resolution PNG images (200 DPI) for OCR.

### Step 2: OCR with Alibaba Cloud
Call Alibaba Cloud OCR API to get:
- All text blocks
- Bounding box coordinates for each text block
- Confidence scores

### Step 3: Match Fields to Values
For each field in the field list:
1. Find the field name text block
2. Look for the corresponding value in:
   - **Right side**: Same row, to the right of field name
   - **Below**: Next row, aligned with field name
3. Record field-value pair with both bounding boxes

### Step 4: Generate Redacted PDF
For each matched value:
1. Convert image coordinates to PDF coordinates
2. Draw black rectangle over the value area
3. Keep field name area unchanged

## Field List

The following fields are searched and their values are redacted:

- 法务部归档编号, 归档时间, 申请人工号, 申请人姓名, 申请人部门
- 申请人部门负责人, 所涉项目名称（如有）, 所涉项目编号（如有）
- 对方编号（如有）, 合同编号, 合同名称, 合同甲方名称, 合同乙方名称
- 合同相对方, 相对方所属行业, 相对方是否为世界500强
- 相对方是央企/国企, 相对方是否为涉密单位, 业务类别, 合同类别
- 合同类型, 合同状态, 扫描件状态, 对方是否签章, 我方是否签章
- 销售、采购标的（非一起译填）, 语种, 单价, 合同金额（元）, 币种
- 支付/收款方式, 付款/收款条件, 合同结算周期, 是否使用公司模板
- 用章主体, 印章类型, 签订时间, 合同开始时间, 合同到期时间
- 收支类型, 我方联系人姓名, 我方联系人电话, 对方联系人姓名
- 对方联系人电话, 对方邮寄地址, 归档状态, 开票名称, 开票账号
- 开票银行, 收款名称, 收款账号, 收款银行, 验收时间, 验收标...