Refrax: flat-port refraction removal

Warps an underwater image taken through a flat-port housing into a refraction-free pinhole image, so it can be used directly by tools such as COLMAP. Every pixel is traced through the air–glass–water interfaces onto a scene plane at depth z0, and the resulting map is inverted.

Code · Image-Space Refraction Correction for Underwater 3D Reconstruction: Warping Flat-Port Views into Pinhole Perspective

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Or use your own image

Fit the output to the whole corrected image (otherwise keep the input size) Crop to the largest rectangle without invalid pixels (otherwise the validity mask is the alpha channel) Keep the original image size Resize: long side up to (smaller is faster)

Underwater image

No image

Corrected

Validity mask

new_calibration.yaml

A checkerboard (10×10 squares of 10 cm) at depth z0, seen through the housing with the calibration on the left, then corrected.