what do “fx fy cx cy”mean？

TadasBaltrusaitis / CLM-framework

CLM-framework (a.k.a Cambridge Face Tracker) is a framework for various Constrained Local Model based face tracking and landmark detection algorithms and their extensions/applications. Includes CLM-Z and CLNF.

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what do “fx fy cx cy”mean？ #22

Closed tabsun closed 8 years ago

tabsun commented 8 years ago

I see the arguments input -fx -fy -cx -cy, but I do not know what do these arguments mean? Can anyone give me some explaination?Thank you

TadasBaltrusaitis commented 8 years ago

Hi,

They refer to camera calibration parameters (https://en.wikipedia.org/wiki/Camera_resectioning), specifically fx and fy are the focal lengths and cx, cy represent the camera principal point.

Knowing them accurately is important for head pose estimation, 3D landmark location, and gaze estimation, they do not affect 2D landmark or Action Unit detection.

If these parameters are not specified the code attempts to get a rough 'guesstimate' based on image size.

Thanks, Tadas