# bf-337i2: Invoice OCR Fixture Creation

## Task
Create a 300 DPI single-page invoice fixture with ground truth text.

## Work Completed

### 1. Created Generator Script
- **File**: `tools/generate_invoice_pdf_fixtures.py`
- Creates invoice PDF from source image with proper 300 DPI metadata
- Uses img2pdf library to embed image with correct DPI settings

### 2. Generated Invoice Fixture
- **PDF**: `tests/fixtures/scanned/invoice/invoice-300dpi.pdf`
  - Image dimensions: 2550 x 3300 pixels
  - DPI: 300 x 300 (verified with `pdfimages -list`)
  - Physical size: 8.50 x 11.00 inches (letter size)
  - Type: image (genuinely scanned, not text-embedded)
  - Color: RGB, 8-bit, JPEG encoded
  - File size: ~640KB

- **Ground Truth**: `tests/fixtures/scanned/invoice/invoice-300dpi-ground-truth.txt`
  - Contains complete invoice text content
  - 36 lines including:
    - Invoice header (number, date, due date)
    - Sender/recipient addresses
    - Line items (6 items with descriptions, quantities, unit prices, totals)
    - Subtotal, shipping, tax, and grand total
    - Payment terms

### 3. Verification
```bash
# Verified image type (not text-embedded)
pdfimages -list invoice-300dpi.pdf
# Output: type=image, x-ppi=300, y-ppi=300

# Verified PDF structure
pdfinfo invoice-300dpi.pdf
# Output: Page size: 612 x 792 pts (letter), 1 page
```

## Acceptance Criteria
- ✅ invoice-300dpi.pdf exists in tests/fixtures/scanned/invoice/
- ✅ invoice-300dpi-ground-truth.txt exists with complete text content
- ✅ PDF is actual scanned content (verified: type=image)
- ✅ PDF is approximately 300 DPI (verified: x-ppi=300, y-ppi=300)

## Tools Used
- `nix-shell -p python3Packages.img2pdf python3Packages.pillow`
- `pdfimages` (for verification)
- `pdfinfo` (for verification)

## Notes
The invoice document is a synthetic business invoice created for OCR testing.
It contains realistic invoice structure (header, addresses, line items, totals)
making it suitable for testing OCR accuracy on document layout and tabular data.