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Setting parameters to compute HoG

asked 2016-04-01 11:44:03 -0500

bob409 gravatar image

updated 2016-04-01 13:50:17 -0500

LorenaGdL gravatar image

My image is of size 128x128. Should I use a win_Size of 128x128 as well? And how to select values for the other parameters as well: HOGDescriptor(Size win_size=Size(128, 128), Size block_size=Size(16, 16), Size block_stride=Size(8, 8), Size cell_size=Size(8, 8), int nbins=9, double win_sigma=DEFAULT_WIN_SIGMA, double threshold_L2hys=0.2, bool gamma_correction=true, int nlevels=DEFAULT_NLEVELS)

I have seen the explanation at http://docs.opencv.org/2.4/modules/gp... but it is not clear enough on how to set the parameters properly.

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answered 2016-04-01 13:51:49 -0500

LorenaGdL gravatar image

When you say your image you mean a positive sample? You should use a win_size equal the size of your positive samples. You can leave default values for the rest of the params to start, they're reasonable enough to give you good results

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Thnks. Should I normalize the feature vector afterwards or it is already normalized?

bob409 gravatar imagebob409 ( 2016-04-01 19:56:48 -0500 )edit

It has some internal normalization, but I usually perform a secondary normalization. In my case, results were almost the same (little better with normalization), others report more significant improvements with the additional normalization.

LorenaGdL gravatar imageLorenaGdL ( 2016-04-02 03:51:40 -0500 )edit

How to normalize hog feature?

bob409 gravatar imagebob409 ( 2016-04-02 04:48:20 -0500 )edit
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Asked: 2016-04-01 11:44:03 -0500

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Last updated: Apr 01 '16