# ocr-processing Specification

## Purpose
TBD - created by archiving change frontend-adjustable-ppstructure-params. Update Purpose after archive.
## 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 center-point and IoU
- **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 its center point falls inside any PP-StructureV3 element bbox
- **OR** if IoU with any PP-StructureV3 element exceeds 0.15 threshold
- **AND** regions not meeting either criterion SHALL be marked as uncovered

#### 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 prevents repeated text
- **GIVEN** a Raw OCR region being considered for supplementation
- **WHEN** the region has IoU > 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 Track Isolation

The gap filling feature SHALL only apply to OCR track processing and SHALL NOT affect Direct or Hybrid track outputs.

#### Scenario: Gap filling only activates for OCR track
- **GIVEN** a document processing task
- **WHEN** the processing track is OCR
- **THEN** the system SHALL evaluate and apply gap filling as needed
- **AND** produce enhanced output with supplemented content

#### Scenario: Direct track is unaffected
- **GIVEN** a document processing task with Direct track
- **WHEN** the task is processed
- **THEN** the system SHALL NOT invoke any gap filling logic
- **AND** produce output identical to current Direct track behavior

#### Scenario: Hybrid track is unaffected
- **GIVEN** a document processing task with Hybrid track
- **WHEN** the task is processed
- **THEN** the system SHALL NOT invoke gap filling logic
- **AND** use existing Hybrid track processing pipeline

### 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: IoU thresholds are configurable
- **GIVEN** custom IoU thresholds configured:
  - gap_filling_iou_threshold: 0.2
  - gap_filling_dedup_iou_threshold: 0.6
- **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

### Requirement: Layout Model Selection
The system SHALL allow users to select a layout detection model optimized for their document type, providing a simple choice between pre-configured models instead of manual parameter tuning.

#### Scenario: User selects Chinese document model
- **GIVEN** a user is processing Chinese business documents (forms, contracts, invoices)
- **WHEN** the user selects "Chinese Document Model" (PP-DocLayout-S)
- **THEN** the OCR engine SHALL use the PP-DocLayout-S layout detection model
- **AND** the model SHALL be optimized for 23 Chinese document element types
- **AND** table and form detection accuracy SHALL be improved over the default model

#### Scenario: User selects standard model for English documents
- **GIVEN** a user is processing English academic papers or reports
- **WHEN** the user selects "Standard Model" (PubLayNet-based)
- **THEN** the OCR engine SHALL use the default PubLayNet-based layout detection model
- **AND** the model SHALL be optimized for English document layouts

#### Scenario: User selects CDLA model for specialized Chinese layout
- **GIVEN** a user is processing Chinese documents with complex layouts
- **WHEN** the user selects "CDLA Model"
- **THEN** the OCR engine SHALL use the picodet_lcnet_x1_0_fgd_layout_cdla model
- **AND** the model SHALL provide specialized Chinese document layout analysis

#### Scenario: Layout model is sent via API request
- **GIVEN** a frontend application with model selection UI
- **WHEN** the user starts task processing with a selected model
- **THEN** the frontend SHALL send the model choice in the request body:
  ```json
  POST /api/v2/tasks/{task_id}/start
  {
    "use_dual_track": true,
    "force_track": "ocr",
    "language": "ch",
    "layout_model": "chinese"
  }
  ```
- **AND** the backend SHALL configure PP-StructureV3 with the corresponding model

#### Scenario: Default model when not specified
- **GIVEN** an API request without `layout_model` parameter
- **WHEN** the task is started
- **THEN** the system SHALL use "chinese" (PP-DocLayout-S) as the default model
- **AND** processing SHALL work correctly without requiring model selection

#### Scenario: Invalid model name is rejected
- **GIVEN** a request with an invalid `layout_model` value
- **WHEN** the user sends `layout_model: "invalid_model"`
- **THEN** the API SHALL return 422 Validation Error
- **AND** provide a clear error message listing valid model options

### Requirement: Layout Model Selection UI
The frontend SHALL provide a simple, user-friendly interface for selecting layout detection models with clear descriptions of each option.

#### Scenario: Model options are displayed with descriptions
- **GIVEN** the model selection UI is displayed
- **WHEN** the user views the available options
- **THEN** the UI SHALL show the following options:
  - "Chinese Document Model (Recommended)" - for Chinese forms, contracts, invoices
  - "Standard Model" - for English academic papers, reports
  - "CDLA Model" - for specialized Chinese layout analysis
- **AND** each option SHALL have a brief description of its use case

#### Scenario: Chinese model is selected by default
- **GIVEN** the user opens the task processing interface
- **WHEN** the model selection is displayed
- **THEN** "Chinese Document Model" SHALL be pre-selected as the default
- **AND** the user MAY change the selection before starting processing

#### Scenario: Model selection is visible only for OCR track
- **GIVEN** a document processing interface
- **WHEN** the user selects processing track
- **THEN** layout model selection SHALL be shown ONLY when OCR track is selected or auto-detected
- **AND** SHALL be hidden for Direct track (which does not use PP-StructureV3)

### Requirement: Model Cache Cleanup

The system SHALL provide documentation for cleaning up unused model caches to optimize storage space.

#### Scenario: User wants to free disk space after model upgrade
- **WHEN** the user has upgraded from older models (PP-DocLayout-S, SLANet) to newer models
- **THEN** the documentation SHALL explain how to delete unused cached models from `~/.paddlex/official_models/`
- **AND** list which model directories can be safely removed