Creates polygons from input raster features. One polygon is output for each contiguous area of cells with the same value in all bands.

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Typical Uses

  • Converting raster images to a set of polygons.
  • Vectorizing raster data for vector geoprocessing.

How does it work?

The RasterToPolygonCoercer accepts raster input features. Polygons are traced around the edges of cells (pixels), enclosing areas with identical band values. Donuts are created where contiguous areas contains islands of differing values.

Nodata cells may either be included or excluded.

Output polygons may retain the raster’s attributes, and may also have a new Label Attribute added, containing the band values represented as a comma-separated list.

This transformer supports raster band selection. The RasterSelector can be used to modify selection.


Usage Notes

  • If memory usage becomes an issue while using this transformer, try adding a RasterCheckpointer before the RasterToPolygonCoercer.
  • If you need a polygon for each pixel in the raster, consider using the RasterCellCoercer.

Choosing a Raster Transformer

FME has an extensive selection of transformers for working with raster data. They can be generally categorized as working with whole rasters, bands, cells or palettes, and those designed for workflow control or combining raster with vector data.

For information on raster geometry and properties, see Rasters (IFMERaster).


Input Ports

Output Ports


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.

Dialog Options - Tables

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


Processing Behavior


Feature Holding


Dependencies None

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