How is full convolution performed using MATLAB's conv2 function?
<p>I am trying to get some input on MATLAB's <code>conv2</code> function.  Suppose that we have an image <code>I</code> of dimensions <code>5 x 5</code> and a kernel <code>K</code> that is <code>3 x 3</code>.</p>

<p><code>conv2(I,K)</code> would return a <code>7 x 7</code> matrix. What extra operations are being done that I am not aware of? I can totally understand how <code>conv2(I,K,'valid')</code> and <code>conv2(I,K,'same')</code> works from a mathematical point of view.  However, the default operation returns a larger matrix. Does anyone know what it actually does? </p>