Tuesday, July 16, 2019

GoPro Virtual Lens

Grab the image with your mouse to reframe the image.
Within the shader code above is the math to simulate GoPro lens look within 360° source.  The same math is very useful for "correcting" lens distortion.  The shader code is licensed under MIT or Apache 2.0. 
I would love someone in the comments to convert the lens radial distortion equation phi = 85.6r - 10.91r² to a OpenCV lens model. GoPro uses n-order radial distortion polynomial in the form: angle° = Ar + Br² + Cr³ where 'r' is the normalized sensor radius. OpenCV uses something more common, but I'm too lazy to learn, so I seek your help. To get OpenCV model started, here is the lens model in odd powers phi = 83.90432r - 18.26919r3 + 15.51541r5 - 6.51824r.

Thursday, May 09, 2019

Know Your Fisheyes

When you say a GoPro is a fisheye lens, which one do you mean?  GoPro is less "fisheye" than you likely thought, somewhere between stereographic and a rectilinear (non-fisheye, pin-pole style lens -- the one people say is non-distorted.)