# Identification

## Identification through correlation

Correlation is about finding all the places in an image where a subimage appears:

$f\left(x,y\right)\circ w\left(x,y\right)⇔F\left(u,v\right)H*\left(u,v\right)$

What this operation is telling us is, that the spatial correlation can be achieved through the multiplication of the Fourier transform of the image by the conjugate transform of the subimage.

In MATLAB, the process of correlation is done through the following command:

g = dftcorr(f,w)

where g is the resulting image from the process, f is the original image, and w is the subimage.

You can practice these concepts using snippet09.