c12ea0b9f6
Problem: PP-Structure misses tables with faint lines/borders Solution: Preprocess images (contrast, sharpen) for layout detection - Preprocessed image only used for layout detection - Original image preserved for element extraction (quality) Includes: proposal.md, design.md, tasks.md, spec delta 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
56 lines
2.6 KiB
Markdown
56 lines
2.6 KiB
Markdown
## ADDED Requirements
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### Requirement: Layout Detection Image Preprocessing
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The system SHALL provide optional image preprocessing to enhance layout detection accuracy for documents with faint lines, low contrast, or poor scan quality.
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#### Scenario: Preprocessing improves table detection
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- **GIVEN** a document with faint table borders that PP-Structure fails to detect
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- **WHEN** layout preprocessing is enabled
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- **THEN** the system SHALL preprocess the image before layout detection
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- **AND** contrast enhancement SHALL make faint lines more visible
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- **AND** PP-Structure SHALL receive the preprocessed image for layout detection
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#### Scenario: Image element extraction uses original quality
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- **GIVEN** an image element detected by PP-Structure from preprocessed input
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- **WHEN** the system extracts the image element
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- **THEN** the system SHALL crop from the ORIGINAL image, not the preprocessed version
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- **AND** the extracted image SHALL maintain original quality and colors
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#### Scenario: Preprocessing can be disabled
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- **GIVEN** `layout_preprocessing_enabled` is set to false in configuration
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- **WHEN** OCR track processing runs
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- **THEN** the system SHALL skip preprocessing
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- **AND** PP-Structure SHALL receive the original image directly
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#### Scenario: CLAHE contrast enhancement
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- **WHEN** `layout_preprocessing_contrast` is set to "clahe"
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- **THEN** the system SHALL apply Contrast Limited Adaptive Histogram Equalization
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- **AND** the enhancement SHALL not over-saturate already bright regions
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#### Scenario: Sharpening enhances faint lines
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- **WHEN** `layout_preprocessing_sharpen` is enabled
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- **THEN** the system SHALL apply unsharp masking to enhance edges
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- **AND** faint table borders SHALL become more detectable
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#### Scenario: Optional binarization for extreme cases
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- **WHEN** `layout_preprocessing_binarize` is enabled
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- **THEN** the system SHALL apply adaptive thresholding
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- **AND** this SHALL be used only for documents with very poor contrast
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### Requirement: Preprocessing Track Isolation
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The layout preprocessing feature SHALL only affect layout detection input without impacting other processing components.
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#### Scenario: Raw OCR is unaffected
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- **GIVEN** layout preprocessing is enabled
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- **WHEN** Raw OCR processing runs
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- **THEN** Raw OCR SHALL use the original image
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- **AND** text detection quality SHALL not be affected by preprocessing
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#### Scenario: Preprocessed image is temporary
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- **GIVEN** an image is preprocessed for layout detection
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- **WHEN** layout detection completes
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- **THEN** the preprocessed image SHALL NOT be persisted to storage
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- **AND** only the original image and element crops SHALL be saved
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