In open CV Why is the default Gabor phase offset 90 degrees?

Question

This is using the default (CV_PI*0.5,) phase offset getGaborKernel(size, 8.0, 0.0, 16.0, 1.0);

This is using a zero phase offset getGaborKernel(size, 8.0, 0.0, 16.0, 1.0, 0.0);

So it seems that default phase offset (90 deg) removes the symmetry of the Gabor kernel. I have seen some other references where they use the same offset so I guess its standard conversion.

Why is this the default? Is it generally more useful to have this for feature extraction?

Also asked on the open CV Q&A site.

Answer 1

I think yes, the first case is more useful then the second one. Because first filter is edge detector, while second one is line detector. You can compose line detector from two edge detectors.

So, edges is more usefull (more general case) for feature extractor, that's why I think phase offset 90 deg is default parameter.