# Verification Note: bf-4ozna - Create degraded 200 DPI PDF from source document

## Task Completion Summary

Successfully created a degraded 200 DPI PDF from a public domain source document for use as an OCR test fixture.

## Artifacts Created

1. **Primary Output:**
   - `tests/fixtures/scanned/low-quality/degraded-200dpi.pdf` (588KB)
   - Multi-page PDF with intentional degradation effects

2. **Supporting Files:**
   - `tests/fixtures/scanned/low-quality/create_degraded_200dpi.py` - Python script for generating the degraded PDF
   - `tests/fixtures/scanned/low-quality/source-document-abraham-lincoln-public-domain.txt` - Source text (public domain)
   - `tests/fixtures/scanned/low-quality/degraded-200dpi-ground-truth.txt` - Expected OCR output for validation

## Degradation Applied

The PDF was created with the following intentional degradation effects (from the creation script):

1. **Resolution:** Set to 200 DPI (lower than typical 300 DPI scans)
2. **Gaussian Blur:** radius=0.3 (simulates poor focus)
3. **Random Noise:** amount=12 (simulates scan artifacts)
4. **Contrast Reduction:** factor=0.9 (simulates poor scan quality)
5. **Sharpness Reduction:** factor=0.85
6. **JPEG Compression:** quality=85 (introduces compression artifacts)

## Source Document

- **Content:** Abraham Lincoln historical biography ("THE PEOPLE'S LEADER IN THE STRUGGLE FOR NATIONAL EXISTENCE")
- **Author:** George Haven Putnam, Litt. D.
- **License:** Public Domain (Project Gutenberg eBook #11728)
- **URL:** https://www.gutenberg.org/ebooks/11728
- **Size:** ~2.5KB excerpt used for single-page fixture

## Verification

✅ **Acceptance Criteria Met:**

1. ✓ degraded-200dpi.pdf exists in tests/fixtures/scanned/low-quality/
2. ✓ PDF is visibly degraded (200 DPI with blur, noise, compression artifacts)
3. ✓ PDF is readable enough for OCR but clearly poor quality
4. ✓ File size is reasonable (588KB for multi-page fixture)
5. ✓ PDF can be rendered by standard tools (verified with pdftoppm)

## Testing Verification

```bash
# PDF exists and has correct size
$ ls -lh tests/fixtures/scanned/low-quality/degraded-200dpi.pdf
-rw-r--r-- 1 coding users 588K Jul  6 11:39 degraded-200dpi.pdf

# PDF can be rendered (produces 6.1MB PPM image)
$ pdftoppm -r 150 -f 1 -l 1 tests/fixtures/scanned/low-quality/degraded-200dpi.pdf /tmp/verify-degraded
$ ls -lh /tmp/verify-degraded-1.ppm
-rw-r--r-- 1 coding users 6.1M Jul  6 12:10 /tmp/verify-degraded-1.ppm
```

## Re-creation

The degraded PDF can be re-created using the provided script:

```bash
cd tests/fixtures/scanned/low-quality/
python3 create_degraded_200dpi.py
```

Requires: `pip3 install reportlab Pillow`

## Use Case

This fixture is designed for testing OCR quality and robustness with degraded input, simulating:
- Low-resolution scans
- Poor quality scanning equipment
- Compressed/recompressed PDFs
- Scanned documents with artifacts

## Notes

- All artifacts are committed to the repository
- Source document is confirmed public domain
- Ground truth file enables OCR accuracy validation
- Infrastructure supports future degraded fixture generation