Implement step 5 (white-border padding: 10 px on all sides), wire all
preprocessing steps into the final preprocess(input, ImageSource) ->
GrayImage entry point, and curate fixtures for the three image-source
paths (PhysicalScan / DigitalOrigin / Jbig2).
Changes:
- Add add_border_padding() function: creates (width+20) x (height+20)
image with 10px white border on all sides
- Add preprocess() pipeline orchestrator: applies deskew, contrast
normalization, binarization, denoising, and padding in correct order
- Skip contrast, binarization, and denoising for JBIG2 images
- Generate test fixtures for skewed_2deg, uneven_lighting, clean_digital,
and jbig2_scan scenarios
- Add integration tests for all critical test scenarios
- Add A4-page benchmarks targeting < 500ms for physical/digital, < 200ms
for JBIG2
Refs:
- Plan section: Phase 5.3 step 5 (line 1878) + critical tests (lines 1882-1885)
- Bead: pdftract-27n3
- Note: notes/pdftract-27n3.md
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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