Last Modified: January 12, 2018

Filters a signal with a specific structure element using a mathematical morphological filter.

Method by which to extend the input signal at both ends of the sequence.

Name | Value | Description |
---|---|---|

Zero padding | 0 | Extends the input signal by padding zeros at both ends of the original signal. |

Symmetric | 1 | Extends the input signal to form a new sequence that is symmetric at both ends of the original signal. |

Periodic | 2 | Extends the input signal to form a new sequence that is periodic at both ends of the original signal. |

Filtering a Signal with the Zero Padding Method

Filtering a Signal with the Symmetric Method

Filtering a Signal with the Periodic Method

**Default: **Zero padding

Structure element to use in the filtering process.

Fundamental operation of the morphological filter.

Name | Value | Description |
---|---|---|

Dilation | 0 | Specifies to perform dilation on the input signal. |

Erosion | 1 | Specifies to perform erosion on the input signal. |

Algorithm and Example for the Dilation Operation

The dilation of a 1D signal *f* is defined as follows:

$D\left(i\right)=\mathrm{max}\left\{x(i-j)+s\left(j\right)\right\},\text{\hspace{0.17em}}\text{\hspace{0.17em}}0\le i\le n-1,\text{\hspace{0.17em}}0\le j\le k-1$

where *x*(*i*) is the *i*th element in the input signal and *s*(*j*) is the *j*th element in **structure element**.

The following image shows an example of the dilation effect. The original signal consists of two pulses with widths of 20, and the **structure element** is an array of ten zeros. The filtered signal expands the pulses in the original signal.

Algorithm and Example for the Erosion Operation

The erosion of a 1D signal *f* is defined as follows:

$E\left(i\right)=\mathrm{min}\left\{x(i+j)-s\left(j\right)\right\},\text{\hspace{0.17em}}\text{\hspace{0.17em}}0\le i\le n-1,\text{\hspace{0.17em}}0\le j\le k-1$

where *x*(*i*) is the *i*th element in the input signal and *s*(*j*) is the *j*th element in **structure element**.

The following image shows an example of the erosion effect. The original signal consists of two pulses with widths of 20, and the **structure element** is an array of ten zeros. The filtered signal shrinks the pulses in the original signal.

**Default: **Dilation

Error conditions that occur before this node runs.

The node responds to this input according to standard error behavior.

Standard Error Behavior

Many nodes provide an **error in** input and an **error out** output so that the node can respond to and communicate errors that occur while code is running. The value of **error in** specifies whether an error occurred before the node runs. Most nodes respond to values of **error in** in a standard, predictable way.

**Default: **No error

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior

**error in** input and an **error out** output so that the node can respond to and communicate errors that occur while code is running. The value of **error in** specifies whether an error occurred before the node runs. Most nodes respond to values of **error in** in a standard, predictable way.

**Where This Node Can Run: **

Desktop OS: Windows

FPGA: Not supported

Web Server: Not supported in VIs that run in a web application