pyramid_reduce, about sigma (down sampling) [closed]

asked 2020-03-18 09:17:22 -0600

swkim gravatar image

Hi, I've studied SIFT and I reach here.

I know that gaussian blurring precedes down-sampling because of anti-aliasing.

from this link, 'https://scikit-image.org/docs/0.7.0/a...' , please see pyramid_reduce.

and the explanation is that

'sigma : float, optional Sigma for the gaussian filter. Default is 2 * downscale / 6.0 which corresponds to a filter mask twice the size of the scale factor that covers more than 99% of the gaussian distribution.'

I don't understand this sentence.

I know that 6sigma range includes 99% region of Gaussian distribution so, kernel size should be 6isgma. ex) sigma = 1, kernel size = 6sigma = 6 but, should be odd value, finally kernel size = 7

Can you explain to me the reason?

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Closed for the following reason question is off-topic or not relevant by berak
close date 2020-03-18 09:31:37.750283

Comments

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sorry, but we cannot help you with scikit's implementation -- this is opencv !

berak gravatar imageberak ( 2020-03-18 09:31:13 -0600 )edit
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