152 lines
7.1 KiB
Markdown
152 lines
7.1 KiB
Markdown
# document-processing Specification Delta
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## ADDED Requirements
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### Requirement: Table Cell Merging Detection
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The system SHALL correctly detect and preserve merged cells (rowspan/colspan) when extracting tables from PDF documents.
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#### Scenario: Detect merged cells in Direct Track
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- **WHEN** extracting tables from an editable PDF using Direct Track
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- **THEN** the system SHALL use PyMuPDF find_tables() API
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- **AND** correctly identify cells with rowspan > 1 or colspan > 1
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- **AND** preserve merge information in UnifiedDocument table structure
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- **AND** skip placeholder cells that are covered by merged cells
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#### Scenario: Handle complex table structures
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- **WHEN** processing a table with mixed merged and regular cells (e.g., edit3.pdf with 83 cells including 121 merges)
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- **THEN** the system SHALL NOT split merged cells into individual cells
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- **AND** the output cell count SHALL match the actual visual cell count
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- **AND** the rendered PDF SHALL display correct merged cell boundaries
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### Requirement: Visual Element Path Preservation
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The system SHALL preserve image paths for all visual element types during OCR conversion.
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#### Scenario: Preserve CHART element paths
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- **WHEN** converting PP-StructureV3 output containing CHART elements
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- **THEN** the system SHALL treat CHART as a visual element type
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- **AND** extract saved_path from the element data
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- **AND** include saved_path in the UnifiedDocument content field
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#### Scenario: Support all visual element types
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- **WHEN** processing visual elements of types IMAGE, FIGURE, CHART, DIAGRAM, LOGO, or STAMP
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- **THEN** the system SHALL extract saved_path or img_path for each element
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- **AND** preserve path, width, height, and format in content dictionary
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- **AND** enable downstream PDF generation to embed these images
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#### Scenario: Fallback path resolution
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- **WHEN** a visual element has multiple path fields (saved_path, img_path)
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- **THEN** the system SHALL prefer saved_path over img_path
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- **AND** fallback to img_path if saved_path is missing
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- **AND** log warning if both paths are missing
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### Requirement: Cell Box Coordinate Validation
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The system SHALL validate cell box coordinates from PP-StructureV3 and handle out-of-bounds cases.
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#### Scenario: Detect out-of-bounds coordinates
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- **WHEN** processing cell_boxes from PP-StructureV3
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- **THEN** the system SHALL validate each coordinate against page boundaries (0, 0, page_width, page_height)
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- **AND** log tables with coordinates exceeding page bounds
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- **AND** mark affected cells for fallback processing
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#### Scenario: Apply CV line detection fallback
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- **WHEN** cell_boxes coordinates are invalid (out of bounds)
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- **THEN** the system SHALL apply OpenCV line detection as fallback
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- **AND** reconstruct table structure from detected lines
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- **AND** include fallback_used flag in table metadata
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#### Scenario: Coordinate normalization
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- **WHEN** coordinates are within page bounds but slightly outside table bbox
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- **THEN** the system SHALL clamp coordinates to table boundaries
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- **AND** preserve relative cell positions
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- **AND** ensure no cells overlap after normalization
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### Requirement: Decoration Image Filtering
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The system SHALL filter out minimal decoration images that do not contribute meaningful content.
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#### Scenario: Filter tiny images by area
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- **WHEN** extracting images from a document
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- **THEN** the system SHALL calculate image area (width x height)
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- **AND** filter out images with area < 200 square pixels
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- **AND** log filtered image count for debugging
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#### Scenario: Configurable filtering threshold
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- **WHEN** processing documents with intentionally small images
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- **THEN** the system SHALL support configuration of minimum image area threshold
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- **AND** default to 200 square pixels if not specified
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- **AND** allow threshold = 0 to disable filtering
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### Requirement: Covering Image Removal
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The system SHALL remove covering/redaction images from the final output.
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#### Scenario: Detect covering rectangles
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- **WHEN** preprocessing a PDF page
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- **THEN** the system SHALL detect black/white rectangles covering text regions
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- **AND** identify covering images by high IoU (> 0.8) with underlying content
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- **AND** mark covering images for exclusion
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#### Scenario: Exclude covering images from rendering
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- **WHEN** generating output PDF
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- **THEN** the system SHALL exclude images marked as covering
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- **AND** preserve the text content that was covered
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- **AND** include covering_images_removed count in metadata
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#### Scenario: Handle both black and white covering
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- **WHEN** detecting covering rectangles
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- **THEN** the system SHALL detect both black fill (redaction style)
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- **AND** white fill (whiteout style)
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- **AND** low-contrast rectangles intended to hide content
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## MODIFIED Requirements
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### Requirement: Enhanced OCR with Full PP-StructureV3
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The system SHALL utilize the full capabilities of PP-StructureV3, extracting all 23 element types from parsing_res_list, with proper handling of visual elements and table coordinates.
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#### Scenario: Extract comprehensive document structure
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- **WHEN** processing through OCR track
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- **THEN** the system SHALL use page_result.json['parsing_res_list']
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- **AND** extract all element types including headers, lists, tables, figures
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- **AND** preserve layout_bbox coordinates for each element
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#### Scenario: Maintain reading order
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- **WHEN** extracting elements from PP-StructureV3
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- **THEN** the system SHALL preserve the reading order from parsing_res_list
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- **AND** assign sequential indices to elements
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- **AND** support reordering for complex layouts
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#### Scenario: Extract table structure
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- **WHEN** PP-StructureV3 identifies a table
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- **THEN** the system SHALL extract cell content and boundaries
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- **AND** validate cell_boxes coordinates against page boundaries
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- **AND** apply fallback detection for invalid coordinates
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- **AND** preserve table HTML for structure
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- **AND** extract plain text for translation
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#### Scenario: Extract visual elements with paths
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- **WHEN** PP-StructureV3 identifies visual elements (IMAGE, FIGURE, CHART, DIAGRAM)
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- **THEN** the system SHALL preserve saved_path for each element
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- **AND** include image dimensions and format
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- **AND** enable image embedding in output PDF
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### Requirement: Generate UnifiedDocument from direct extraction
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The system SHALL convert PyMuPDF results to UnifiedDocument with correct table cell merging.
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#### Scenario: Extract tables with cell merging
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- **WHEN** direct extraction encounters a table
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- **THEN** the system SHALL use PyMuPDF find_tables() API
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- **AND** extract cell content with correct rowspan/colspan
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- **AND** preserve merged cell boundaries
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- **AND** skip placeholder cells covered by merges
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#### Scenario: Filter decoration images
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- **WHEN** extracting images from PDF
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- **THEN** the system SHALL filter images smaller than minimum area threshold
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- **AND** exclude covering/redaction images
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- **AND** preserve meaningful content images
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#### Scenario: Preserve text styling with image handling
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- **WHEN** direct extraction completes
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- **THEN** the system SHALL convert PyMuPDF results to UnifiedDocument
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- **AND** preserve text styling, fonts, and exact positioning
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- **AND** extract tables with cell boundaries, content, and merge info
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- **AND** include only meaningful images in output
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