doc: Add FAQ on reusing OpenCV/Kalibr calibration parameters#4566
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behnamasadi wants to merge 1 commit into
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doc: Add FAQ on reusing OpenCV/Kalibr calibration parameters#4566behnamasadi wants to merge 1 commit into
behnamasadi wants to merge 1 commit into
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Documents the 0.5-pixel principal-point offset between COLMAP's corner-origin convention and the pixel-center convention used by OpenCV and Kalibr, plus the OPENCV/FULL_OPENCV distortion parameter order. Addresses recurring confusion in colmap#2587.
ahojnnes
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July 21, 2026 08:20
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Summary
Adds a FAQ entry for a recurring question (#2587, also raised for Kalibr) on
reusing externally-calibrated intrinsics in COLMAP:
pixel center is at
(0.5, 0.5), a centered principal point is(width/2, height/2)), whereas OpenCV/Kalibr use pixel-center integercoordinates. The principal point therefore shifts by
+0.5in both axes(
cx_colmap = cx_opencv + 0.5); focal lengths and distortion coefficientstransfer unchanged.
OPENCV/FULL_OPENCVmodels.Verified against
Camera::CreateFromModelId/CameraModelInitializeParams(principal point is initialized at
width/2, height/2). Docs build cleanly withSphinx.