Technical Documentation: Map Editor (Masking)

Architecture

The Masking Screen utilizes a drawing canvas overlayed on the MapView. It manages a list of Shape objects that are converted into a binary mask for the ROS navigation stack.

Technical Details

• File Path: lib/screens/mask_screen.dart
• Data Models:
  • MaskShape: Stores type (Rect/Circle/Poly), origin coordinates, dimensions, and rotation.
• Coordinate System:
  • Screen Pixels: Where the user touches.
  • Map Data Space: The actual index in the OccupancyGrid.
  • ROS World Space: Transformed meters (Mers) using the map resolution and origin offset.

Implementation Logic

• Shape Drawing: The MaskPainter class uses CustomPainter to render the user's shapes in real-time.
• Mask Generation:
  • When saved, the system iterates through every cell in the OccupancyGrid.
  • It performs a "Point-in-Shape" test for each cell.
  • If a cell falls inside a "No-Go" shape, its value is set to 100 (Obstacle).
• Backend Sync: The final modified OccupancyGrid is sent to the /api/map/mask endpoint, which generates a new .pgm file on the filesystem and reloads the ROS map server.

Performance

• Tiling: For large maps (4K+), the masking logic utilizes tiling to process sections in parallel, preventing UI freezes during the "Apply" phase.