# The reference of the function cvCamShift ?

Hello,

CamShift Finds object center, size, and orientation int cvCamShift( const CvArr* prob_image, CvRect window, CvTermCriteria criteria, CvConnectedComp* comp, CvBox2D* box=NULL );

The function cvCamShift implements CAMSHIFT object tracking algrorithm ([Bradski98]). [Bradski98] G.R. Bradski. Computer vision face tracking as a component of a perceptual user interface.

but formula in the source code "Cvcamshift.cpp" that calculating width, length and orientation is differnet as the ref described.

```
inv_m00 = 1. / m00;
xc = cvRound( m10 * inv_m00 + windowIn.x );
yc = cvRound( m01 * inv_m00 + windowIn.y );
a = mu20 * inv_m00;
b = mu11 * inv_m00;
c = mu02 * inv_m00;
/* Calculating width & height */
square = sqrt( 4 * b * b + (a - c) * (a - c) );
/* Calculating orientation */
theta = atan2( 2 * b, a - c + square );
/* Calculating width & length of figure */
cs = cos( theta );
sn = sin( theta );
rotate_a = cs * cs * mu20 + 2 * cs * sn * mu11 + sn * sn * mu02;
rotate_c = sn * sn * mu20 - 2 * cs * sn * mu11 + cs * cs * mu02;
length = sqrt( rotate_a * inv_m00 ) * 4;
width = sqrt( rotate_c * inv_m00 ) * 4;
```

I want to know which ref is about this part?

Thanks all,

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