Apply the 2-D FIR filter b to x. If the argument shape is specified, return an array of the desired shape. Possible values are:
- 'full'
- pad x with zeros on all sides before filtering.
- 'same'
- unpadded x (default)
- 'valid'
- trim x after filtering so edge effects are no included.
Note this is just a variation on convolution, with the parameters reversed and b rotated 180 degrees.
See also: conv2