ReScape

ReScape removes perspective distortion from coral reefscape images by transforming them into top-down views, enabling quantitative analysis of reef conditions.

Key Features:

• Camera Lens Calibration: Calibrates the camera lens to correct for optical properties.
• Lens Distortion Removal: Removes inherent lens-induced image distortions.
• Horizon Detection: Detects the scene's horizon line in reefscape images.
• Camera-Roll Correction: Removes the camera-roll angle from images.
• Reef Area Detection: Detects the transformable reef area within the image.
• Perspective Geometry Detection: Detects the scene's perspective geometry.
• Inverse-Perspective Mapping: Applies brute-force inverse-perspective mapping to transform images into top-down views.
• Validation by Transect Analysis: Validates transformations by demonstrating that same-length transects placed at varying distances from the camera become equal length after transformation.

Scientific Applications:

• Historical Reef Condition Analysis: Unlocks historical information about coral-reef conditions from previously unquantified periods and localities.
• Citizen Science Contribution: Enables citizen scientists and recreational photographers to contribute reefscape images to the scientific process.
• Large-Scale Ecosystem Survey: Provides a survey technique to rigorously assess relatively large areas of coral reefs, other marine ecosystems, and terrestrial ecosystems worldwide.
• Coral Reef Monitoring: Supports improved management and prediction of coral reef futures through historical archive analysis and rapid survey methods.

Methodology:

ReScape implements inverse-perspective mapping through seven sequential functions: (1) camera lens calibration, (2) removal of lens-induced image distortions, (3) horizon line detection, (4) camera-roll angle removal, (5) transformable reef area detection, (6) perspective geometry detection, and (7) brute-force inverse-perspective mapping application. The algorithm was evaluated on 125 reefscape images, with 85% having no processing errors and 95% of those successfully transformed into top-down views.