FreeMat
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Section: Signal Processing Functions
The conv2
function performs a two-dimensional convolution of matrix arguments. The syntax for its use is
Z = conv2(X,Y)
which performs the full 2-D convolution of X
and Y
. If the input matrices are of size [xm,xn]
and [ym,yn]
respectively, then the output is of size [xm+ym-1,xn+yn-1]
. Another form is
Z = conv2(hcol,hrow,X)
where hcol
and hrow
are vectors. In this form, conv2
first convolves Y
along the columns with hcol
, and then convolves Y
along the rows with hrow
. This is equivalent to conv2(hcol(:)*hrow(:)',Y)
.
You can also provide an optional shape
argument to conv2
via either
Z = conv2(X,Y,'shape') Z = conv2(hcol,hrow,X,'shape')
where shape
is one of the following strings
'full'
- compute the full convolution result - this is the default if no shape
argument is provided. 'same'
- returns the central part of the result that is the same size as X
. 'valid'
- returns the portion of the convolution that is computed without the zero-padded edges. In this situation, Z
has size [xm-ym+1,xn-yn+1]
when xm>=ym
and xn>=yn
. Otherwise conv2
returns an empty matrix. The convolution is computed explicitly using the definition:
If the full output is requested, then m
ranges over 0 <= m < xm+ym-1
and n
ranges over 0 <= n < xn+yn-1
. For the case where shape
is 'same'
, the output ranges over (ym-1)/2 <= m < xm + (ym-1)/2
and (yn-1)/2 <= n < xn + (yn-1)/2
.