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wrong formula of orientation feature in documentation? #64

@AEttinger

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@AEttinger

Hello,

I'm currently trying to re-implement some of the Weka features in Python and had trouble to reproduce the orientation feature based on the Hessian matrix. After some digging, I found that the formula on the documentation page [ 1/2 arccos(4b^2 + (a - d)^2) ] does not match the one used in FeatureStack.java [ -0.5 * Math.acos((s_xx - s_yy) / Math.sqrt(4.0 * s_xy * s_xy + (s_xx - s_yy) * (s_xx - s_yy))) ]. Using the Feature Stack implementation, my result is now much more comparable to the output of the Weka plugin in Fiji, so I assume that this is being used.
I wanted to bring this to your attention, just in case somebody else stumbles over this. It may be good to change it on the documentation page.

Thank you very much.
Andreas

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