Cirrus Logic CS485 Specifiche Scaricare il pdf (Pagina 257)

100

101

Image Statistics Functions

12-5

Image Moments

Spatial and central moments are important statistical characteristics of an

image. The spatial moment M

(m,n) and central moment U

(m,n)are

defined as follows:

()

Mmn xyP

nRows

nCols

−

∑∑

()

Umn x x y y P

nRows

nCols

=−−

−

∑∑

where the summation is performed for all rows and columns in the image;

j,k

are pixel values; x

and y

are pixel coordinates; m and n are integer

power exponents; x

and y

are the gravity center’s coordinates:

= M

(1,0)/M

(0,0)

= M

(0,1)/M

(0,0).

The sum of exponents m + n is called the moment order. The library

functions support moments of order 0 to 3 (that is, 0

≤ m + n ≤ 3).

In the Image Processing Library image moments are stored in structures of

the

IplMomentState type. The type declaration is given below.

IplMomentState Structure Definition

typedef struct {

double scale /* scaling factor for the moment */

double value /* the moment */

} ownMoment;

typedef ownMoment IplMomentState[4][4];

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