## MODIFIED Requirements

### Requirement: OCR Track Gap Filling with Raw OCR Regions

The system SHALL detect and fill gaps in PP-StructureV3 output by supplementing with Raw OCR text regions when significant content loss is detected.

#### Scenario: Gap filling activates when coverage is low
- **GIVEN** an OCR track processing task
- **WHEN** PP-StructureV3 outputs elements that cover less than 70% of Raw OCR text regions
- **THEN** the system SHALL activate gap filling
- **AND** identify Raw OCR regions not covered by any PP-StructureV3 element
- **AND** supplement these regions as TEXT elements in the output

#### Scenario: Coverage is determined by IoA (Intersection over Area)
- **GIVEN** a Raw OCR text region with bounding box
- **WHEN** checking if the region is covered by PP-StructureV3
- **THEN** the region SHALL be considered covered if IoA (intersection area / OCR box area) exceeds the type-specific threshold
- **AND** IoA SHALL be used instead of IoU because it correctly measures "small box contained in large box" relationship
- **AND** regions not meeting the IoA criterion SHALL be marked as uncovered

#### Scenario: Element-type-specific IoA thresholds are applied
- **GIVEN** a Raw OCR region being evaluated for coverage
- **WHEN** comparing against PP-StructureV3 elements of different types
- **THEN** the system SHALL apply different IoA thresholds:
  - TEXT, TITLE, HEADER, FOOTER: IoA > 0.6 (tolerates boundary errors)
  - TABLE: IoA > 0.1 (strict filtering to preserve table structure)
  - FIGURE, IMAGE: IoA > 0.8 (preserves text within figures like axis labels)
- **AND** a region is considered covered if it meets the threshold for ANY overlapping element

#### Scenario: Only TEXT elements are supplemented
- **GIVEN** uncovered Raw OCR regions identified for supplementation
- **WHEN** PP-StructureV3 has detected TABLE, IMAGE, FIGURE, FLOWCHART, HEADER, or FOOTER elements
- **THEN** the system SHALL NOT supplement regions that overlap with these structural elements
- **AND** only supplement regions as TEXT type to preserve structural integrity

#### Scenario: Supplemented regions meet confidence threshold
- **GIVEN** Raw OCR regions to be supplemented
- **WHEN** a region has confidence score below 0.3
- **THEN** the system SHALL skip that region
- **AND** only supplement regions with confidence >= 0.3

#### Scenario: Deduplication uses IoA instead of IoU
- **GIVEN** a Raw OCR region being considered for supplementation
- **WHEN** the region has IoA > 0.5 with any existing PP-StructureV3 TEXT element
- **THEN** the system SHALL skip that region to prevent duplicate text
- **AND** the original PP-StructureV3 element SHALL be preserved

#### Scenario: Reading order is recalculated after gap filling
- **GIVEN** supplemented elements have been added to the page
- **WHEN** assembling the final element list
- **THEN** the system SHALL recalculate reading order for the entire page
- **AND** sort elements by y0 coordinate (top to bottom) then x0 (left to right)
- **AND** ensure logical document flow is maintained

#### Scenario: Coordinate alignment with ocr_dimensions
- **GIVEN** Raw OCR processing may involve image resizing
- **WHEN** comparing Raw OCR bbox with PP-StructureV3 bbox
- **THEN** the system SHALL use ocr_dimensions to normalize coordinates
- **AND** ensure both sources reference the same coordinate space
- **AND** prevent coverage misdetection due to scale differences

#### Scenario: Supplemented elements have complete metadata
- **GIVEN** a Raw OCR region being added as supplemented element
- **WHEN** creating the DocumentElement
- **THEN** the element SHALL include page_number
- **AND** include confidence score from Raw OCR
- **AND** include original bbox coordinates
- **AND** optionally include source indicator for debugging

### Requirement: Gap Filling Configuration

The system SHALL provide configurable parameters for gap filling behavior.

#### Scenario: Gap filling can be disabled via configuration
- **GIVEN** gap_filling_enabled is set to false in configuration
- **WHEN** OCR track processing runs
- **THEN** the system SHALL skip all gap filling logic
- **AND** output only PP-StructureV3 results as before

#### Scenario: Coverage threshold is configurable
- **GIVEN** gap_filling_coverage_threshold is set to 0.8
- **WHEN** PP-StructureV3 coverage is 75%
- **THEN** the system SHALL activate gap filling
- **AND** supplement uncovered regions

#### Scenario: IoA thresholds are configurable per element type
- **GIVEN** custom IoA thresholds configured:
  - gap_filling_ioa_threshold_text: 0.6
  - gap_filling_ioa_threshold_table: 0.1
  - gap_filling_ioa_threshold_figure: 0.8
  - gap_filling_dedup_ioa_threshold: 0.5
- **WHEN** evaluating coverage and deduplication
- **THEN** the system SHALL use the configured values
- **AND** apply them consistently throughout gap filling process

#### Scenario: Confidence threshold is configurable
- **GIVEN** gap_filling_confidence_threshold is set to 0.5
- **WHEN** supplementing Raw OCR regions
- **THEN** the system SHALL only include regions with confidence >= 0.5
- **AND** filter out lower confidence regions

#### Scenario: Boundary shrinking reduces edge duplicates
- **GIVEN** gap_filling_shrink_pixels is set to 1
- **WHEN** evaluating coverage with IoA
- **THEN** the system SHALL shrink OCR bounding boxes inward by 1 pixel on each side
- **AND** this reduces false "uncovered" detection at region boundaries

## ADDED Requirements

### Requirement: Use PP-StructureV3 Internal OCR Results

The system SHALL preferentially use PP-StructureV3's internal OCR results (`overall_ocr_res`) instead of running a separate Raw OCR inference.

#### Scenario: Extract overall_ocr_res from PP-StructureV3
- **GIVEN** PP-StructureV3 processing completes
- **WHEN** the result contains `json['res']['overall_ocr_res']`
- **THEN** the system SHALL extract OCR regions from:
  - `dt_polys`: detection box polygons
  - `rec_texts`: recognized text strings
  - `rec_scores`: confidence scores
- **AND** convert these to the standard TextRegion format for gap filling

#### Scenario: Skip separate Raw OCR when overall_ocr_res is available
- **GIVEN** gap_filling_use_overall_ocr is true (default)
- **WHEN** PP-StructureV3 result contains overall_ocr_res
- **THEN** the system SHALL NOT execute separate PaddleOCR inference
- **AND** use the extracted overall_ocr_res as the OCR source
- **AND** this reduces total inference time by approximately 50%

#### Scenario: Fallback to separate Raw OCR when needed
- **GIVEN** gap_filling_use_overall_ocr is false OR overall_ocr_res is missing
- **WHEN** gap filling is activated
- **THEN** the system SHALL execute separate PaddleOCR inference as before
- **AND** use the separate OCR results for gap filling
- **AND** this maintains backward compatibility

#### Scenario: Coordinate consistency is guaranteed
- **GIVEN** overall_ocr_res is extracted from PP-StructureV3
- **WHEN** comparing with PP-StructureV3 layout elements
- **THEN** both SHALL use the same coordinate system
- **AND** no additional coordinate alignment is needed
- **AND** this prevents scale mismatch issues
