CenterPointExtractor

Extracts the coordinates of a point located within the feature, its bounding box, or at its center of mass, and stores them as attributes.

Jump to Configuration

Typical Uses

Identifying the center of mass of a feature
Identifying the center of the bounding box of a feature
Identifying locations for annotation

How does it work?

The CenterPointExtractor receives features with any type of geometry and calculates a center point for each feature, according to a choice of Point Extraction Mode. The calculated coordinates are added to the feature as attribute values. Both 2D and 3D geometry are supported.

Aggregates are also supported, with one center point extracted for each aggregate.

Point Placement

The result of each center mode is shown below.

Original areas and their bounding boxes are included for reference.

Mode	Description	Result
	Input Features: Park polygons with their bounding boxes shown in blue.
Center Point of Bounding Box	Points are placed at the center of the feature’s bounding box. Point may fall outside the polygon.
Center of Gravity Point	Points are placed at the center of mass of the feature. Point may fall outside the polygon.
Any Inside Point	Points are placed at an arbitrary location inside the polygon.

Examples

Example: Extracting center point coordinates for a polygon

In this example, we have a set of zoning polygons. Some are aggregates, and some have rather irregular shapes. We want to extract center point coordinates for the features, but ensure that they are positioned within their respective features.

The features are routed into a CenterPointExtractor.

In the parameters dialog, we set Point Extraction Mode to Any Inside Point. Given the irregular shapes, the other options would likely place points outside the polygon boundaries. The X, Y, and Z output attributes are left with their default names.

The output features now have two added attributes - _inside_x and _inside_y. Note that as the features are 2D, and do not have z coordinates, Z did not receive a value.

Note also that this transformer does not alter geometry - it only adds attribute values. To check the position of the point coordinates, we can use a VertexCreator on a copy of the features.

The resulting points fall within their respective polygons.

Usage Notes

This transformer does not alter geometry. To replace a feature with its center point, use a CenterPointReplacer.

Creating and Modifying Point and Text Features

These transformers work with points, text, and labels in a variety of ways.

Points and Text Transformers Comparison

Transformer	Use this to...	Transformer Description
Creator	Create one or more new features with box geometry of a specific size and position (when Geometry Object is Point or Text).	Creates features using the parameters supplied, and sends them into the workspace for processing.
VertexCreator	Replace a feature’s geometry with a point at a specified location.	Creates a single vertex to replace, be appended to, or be inserted into existing geometry.
CenterPointReplacer	Create points inside features or their bounding boxes.	Replaces feature geometry with a point located within the feature, its bounding box, or at its center of mass.
CenterPointExtractor	Extract the coordinates of a calculated point within the feature.	Extracts the coordinates of a point located within the feature, its bounding box, or at its center of mass, and stores them as attributes.
2DGridCreator	Create new regularly-spaced points in a specified location.	Creates a regular grid of points or rectangular polygons of a specified size, position, and coordinate system.
2DGridAccumulator	Create new regularly-spaced points over the extents of other features.	Creates a regular grid of points or rectangular polygons that span the extents of all input features.
Chopper	Create points from every vertex of input line or area geometry.	Chops line, arc, path, or area features into smaller features based on number of vertices or approximate length.
Intersector	Create points where features intersect.	Computes intersections between all input features, breaking lines and polygons wherever an intersection occurs and creating nodes at those locations.
PointCloudToPointCoercer	Create points from point cloud features.	Converts point clouds to point or multipoint geometries, optionally retaining attribute and component values.
Labeller	Label lines.	Places labels along a linear feature, angled to the orientation of each labeled segment.
TextAdder	Label points at an angle.	Replaces any geometry with a single text label at the center of its bounding box.
LabelPointReplacer	Label points and areas.	Replaces point, line, or area geometry with a single text label.
TextLocationExtractor	Convert text to geometry.	Replaces text with its location geometry, usually a point.
TextPropertyExtractor	Extract text properties into attributes.	Retrieves text property values from text geometry, adding them to the feature as attributes.
TextPropertySetter	Set or modify text properties.	Modifies or creates text geometry according to new coordinates, text string, size, or rotation values.
TextStroker	Convert text to non-text geometry.	Converts text to aggregate line or area geometry according to a specific True Type font.
PointPropertyExtractor	Extract point properties into attributes.	Extracts point orientation to feature attributes.
PointPropertySetter	Set or modify point properties.	Adds or removes point orientation.

Labelling and Geometry

Geometry	Recommended Transformer	Example
Point	LabelPointReplacer or TextAdder
Line	Labeller
Area	LabelPointReplacer

Geometry

Recommended Transformer

Example

Point

LabelPointReplacer or TextAdder

Line

Labeller

Area

LabelPointReplacer

Configuration

Input Ports

Output Port

Parameters

Output Attribute Names

X	Name the attribute to contain the x coordinate value of the center point.
Y	Name the attribute to contain the y coordinate value of the center point.
Z	Name the attribute to contain the z coordinate value of the center point.

Editing Transformer Parameters

Transformer parameters can be set by directly entering values, using expressions, or referencing other elements in the workspace such as attribute values or user parameters. Various editors and context menus are available to assist. To see what is available, click beside the applicable parameter.

How to Set Parameter Values

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.

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.

Content Types

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

Table Tools

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.

For more information, see Transformer Parameter Menu Options.

Reference

Processing Behavior	Feature-Based
Feature Holding	No
Dependencies	None
Aliases	InsidePointExtractor
History

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Examples may contain information licensed under the Open Government Licence – Vancouver, Open Government Licence - British Columbia, and/or Open Government Licence – Canada.