Raw & Central Moments

[Johannes Schönberger]

Hi,

instead of:

> x_bar, y_bar = props.centroid

it must be:

> y_bar, x_bar = props.centroid

Hope that helps?

Johannes

Am 06.01.2014 um 13:11 schrieb Jaidev Deshpande <deshpande.jaidev at gmail.com>:

> Hi all,
> 
> According to the wikipedia page on image moments, central moments and raw moments are related as in this link: http://en.wikipedia.org/wiki/Image_moment#Central_moments
> 
> I’ve been trying to examine these relationships using the skimage.measure module.
> 
> I created an ellipse image as per the measure region properties example (http://scikit-image.org/docs/dev/auto_examples/plot_regionprops.html#example-plot-regionprops-py) and rotated it.
> 
> Then I ran the following script:
> 
> from skimage.measure import regionprops, moments, moments_central
> from skimage.morphology import label
> 
> props = regionprops(image) # where `image` is the rotated ellipse
> x_bar, y_bar = props.centroid
> 
> raw_moments = moments(image)
> central_moments = moments_central(image, x_bar, y_bar)
> 
> Now according to the wikipedia page, central_moments[2,0] should be equal to:
> raw_moments[2,0] - x_bar * raw_moments[1,0]
> 
> But that’s not working out. In fact, the value yielded by the above formula is much larger than what skimage says it should be.
> 
> What am I missing?
> 
> Thanks!
> 
> -- 
> JD
> 
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