CenterlineReplacer

Categories

Geometries

Spatial Analysis

Replaces area geometries with their centerlines or straight skeletons. This transformer works best with long, narrow areas.

Example

 

 

Usage Notes

  • Input areas must not self-cross and the region covered by the area must be connected.
  • Z coordinates are ignored by this transformer. All centerlines are 2D.

  • When combined with the Tester, this transformer enables FME to perform area generalization operations.

Configuration

Output Ports

The centerline of the input feature will be output via this port. If the input feature is an aggregate, at least one part was successfully processed, and the algorithm fails to generate a centerline for another part, that part will be left unchanged.

Features that cannot be replaced by their centerline will be output via this port.

Rejected features will have an fme_rejection_code attribute with one of the following values:

INVALID_GEOMETRY

INVALID_GEOMETRY_TYPE

INVALID_POLYGON

INVALID_ELLIPSE

INVALID_DONUT

Parameters

Mode

Centerline: A line is returned that approximates the shape of the original input, and is roughly equidistant to the boundaries on either side.

Straight Skeleton: Every edge segment of the input area’s boundary is moved inwards at a constant speed -- the intersection of the moving segments is returned as the “Straight Skeleton.” Note: this mode returns branches that will touch the edges of the original area.

Note: In the straight skeleton mode, the algorithm may take a long time to run on large or complex input features.

Editing Transformer Parameters

Using a set of menu options, transformer parameters can be assigned by referencing other elements in the workspace. More advanced functions, such as an advanced editor and an arithmetic editor, are also available in some transformers. To access a menu of these options, click beside the applicable parameter. For more information, see Transformer Parameter Menu Options.

Defining Values

There are several ways to define a value for use in a Transformer. The simplest is to simply type in a value or string, which can include functions of various types such as attribute references, math and string functions, and workspace parameters. There are a number of tools and shortcuts that can assist in constructing values, generally available from the drop-down context menu adjacent to the value field.

Using the Text Editor

The Text Editor provides a convenient way to construct text strings (including regular expressions) from various data sources, such as attributes, parameters, and constants, where the result is used directly inside a parameter.

Text Editor

Using the Arithmetic Editor

The Arithmetic Editor provides a convenient way to construct math expressions from various data sources, such as attributes, parameters, and feature functions, where the result is used directly inside a parameter.

Arithmetic Editor

Conditional Values

Set values depending on one or more test conditions that either pass or fail.

Parameter Condition Definition Dialog

Content

Expressions and strings can include a number of functions, characters, parameters, and more.

When setting values - whether entered directly in a parameter or constructed using one of the editors - strings and expressions containing String, Math, Date/Time or FME Feature Functions will have those functions evaluated. Therefore, the names of these functions (in the form @<function_name>) should not be used as literal string values.

String Functions

These functions manipulate and format strings.

Special Characters

 A set of control characters is available in the Text Editor.

Math Functions

Math functions are available in both editors.
Date/Time Functions Date and time functions are available in the Text Editor.

Math Operators

These operators are available in the Arithmetic Editor.

FME Feature Functions

These return primarily feature-specific values.

FME Parameters

FME and workspace-specific parameters may be used.
Creating and Modifying User Parameters Create your own editable parameters.

Dialog Options - Tables

Transformers with table-style parameters have additional tools for populating and manipulating values.

Row Reordering

Enabled once you have clicked on a row item. Choices include:

  • Add a row
  • Remove a row
  • Move current row up one
  • Move current row down one
  • Move current row to top
  • Move current row to bottom

Cut, Copy, and Paste

Enabled once you have clicked on a row item. Choices include:

  • Cut a row - delete and copy to clipboard
  • Copy a row to the clipboard
  • Paste a row from the clipboard

Cut, copy, and paste may be used within a transformer, or between transformers.

Filter

Start typing a string, and the matrix will only display rows matching those characters. Searches all columns. This only affects the display of attributes within the transformer - it does not alter which attributes are output.

Import

Import populates the table with a set of new attributes read from a dataset. Specific application varies between transformers.

Reset/Refresh

Generally resets the table to its initial state, and may provide additional options to remove invalid entries. Behavior varies between transformers.

Note: Not all tools are available in all transformers.

FME Community

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Keywords: abstraction simplification simplify centerline centreline CentreLineReplacer