# How to calculate HuMoments for a contour/image in opencv using c++

hi,

i tried out the following tutorial.I used opencv 2.4.2 with visual studio 2010 and c++.(http://docs.opencv.org/doc/tutorials/imgproc/shapedescriptors/moments/moments.html)

there i can calculate **moments** for each and every contour of the image, like this

```
vector<Moments> mu(contours.size() );
for( int i = 0; i < contours.size(); i++ )
{
mu[i] = moments( contours[i], false );
}
```

then i tried to calculate **Hu-Moments** in the same way. i tried with various combinations, but didn't got it work. My problems are,

- is it possible to calculate
**Hu-Moments**only for a**one contour**? - should i calculate
**Hu-Moments**for the**whole image**?

please can anyone explain this with some examples?