Hybrid Hessian filter does not agree with its original description

[DavidBreuer]

Description

This issue or unclarity was noted in PR #3515 but was not a part of the actual PR:

The available Hybrid Hessian filter does not agree with its description in [1]. In particular, it should not simply be a thresholded version of the Frangi filter but involves different smoothing before the computation of the Hessian eigenvalues (cf. equations (2)-(6) in [1]). Moreover, the implemented thresholding does not agree with the described one (cf. equation (15) in [1]).

Version information

Since this is a general issue of implementation, it does not depend on the used package versions. The Hybrid hessian filter has been introduced in skimage 0.13.

References

[1] Ng, C. C., Yap, M. H., Costen, N., & Li, B. (2014, November). Automatic
wrinkle detection using hybrid Hessian filter. In Asian Conference on Computer
Vision (pp. 609-622). Springer International Publishing.