Can explain the formula for the moment of the contour image?

There is a formula for moment of a contour image
Time is a characteristic of the circuit, the combined (summed) with all pixels of the contour. Point (p,q) is defined as:
Here p is the order of x, q is the order of y, where the order means, so to speak, the power to which the corresponding component is taken in the amount with other displayed.
But I do not quite understand what the formula mean X and U. that is, which they should have values.
People in the know, please explain. The Internet is nothing but the same formula and the same explanation is not found.
July 8th 19 at 16:20
1 answer
July 8th 19 at 16:22
Isn't that a (x,y)-coordinates of i-th point of the contour ?

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