jedarden 691ff10066 docs(bf-10vsm): document generator config structure location

- Identified build/unmapped-glyph-names.json as the primary config file
- Documented DifferencesOverlay struct in encoding.rs as the Rust config structure
- Described the build-time generation process via build.rs
- Listed all files involved in the config pipeline
Closes bf-10vsm

2026-07-06 14:38:34 -04:00

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OCR Output Generation for Degraded 200 DPI Fixture

Task Completed

Successfully generated OCR output text from degraded 200 DPI fixture for WER measurement.

Process Used

Method: External OCR via Tesseract

Since pdftract's built-in OCR feature requires the 'ocr' feature and system dependencies (leptonica-sys), and these dependencies encountered build issues, OCR was generated using the system-installed Tesseract OCR engine.

Commands Executed

Convert PDF to PNG images:
```
pdftoppm -png /home/coding/pdftract/tests/fixtures/scanned/low-quality/degraded-200dpi.pdf degraded-page
```
This created a series of PNG images (degraded-page-1.png, degraded-page-2.png, etc.) in /tmp.

Run OCR on all pages:

for page in degraded-page-*.png; do
    tesseract "$page" - 2>/dev/null
done > /tmp/degraded-200dpi-ocr.txt

This processed each page with Tesseract and combined the output into a single text file.

Save to fixtures directory:

cp /tmp/degraded-200dpi-ocr.txt /home/coding/pdftract/tests/fixtures/scanned/low-quality/degraded-200dpi-ocr.txt

Output File

Location: tests/fixtures/scanned/low-quality/degraded-200dpi-ocr.txt
Size: 2.0K
Lines: 49 lines of text

OCR Quality Assessment

The OCR output successfully extracted readable text from the degraded 200 DPI scan:

Clear recognition of title and author information
Accurate extraction of dates and numbers (February 27, 1860; 1909)
Proper rendering of paragraph structure
Minor OCR artifacts typical of degraded scans (e.g., "M akers" instead of "Makers", "Y ork" instead of "York")

The output is suitable for WER (Word Error Rate) measurement against the ground truth file (tests/fixtures/scanned/low-quality/degraded-200dpi-ground-truth.txt).

Acceptance Criteria Status

✅ PASS: OCR output file is successfully generated from the degraded fixture
✅ PASS: Output file contains readable text (not empty)
✅ PASS: Command used and output file location are documented
✅ PASS: Output file is ready for WER measurement

System Information

Tesseract version: 5.5.0
Leptonica version: 1.85.0
PDF Tools: pdftoppm (poppler-utils)

References

Parent bead: bf-4w3x9
Prerequisite: bf-1bdsf
Fixture source: tests/fixtures/scanned/low-quality/degraded-200dpi.pdf
Ground truth: tests/fixtures/scanned/low-quality/degraded-200dpi-ground-truth.txt

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