Merges multiple raster features into a single raster feature.

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Typical Uses

  • Merging multiple rasters
  • Joining abutting raster tiles together into a single feature
  • Merging overlapping raster features together, blending the overlaps
  • Preparing data for use in operations that require a single raster feature (eg VectorOnRasterOverlayer)

How does it work?

The RasterMosaicker accepts a number of raster features and combines them into a single raster feature.

The input rasters must all have the same number of bands and palettes, or selected bands and palettes.

Each band is individually mosaicked together, and then appended to the output raster. The output raster will have the same number of bands and palettes as the input (whether whole rasters or selected bands/palettes).

If there are gaps in data (that is, areas not covered by any raster), the empty cells will be filled with Nodata values if available, or zero if not.

Bands and Palettes

Rasters may have one band or multiple bands.

Rasters may have no palette, one palette, or multiple palettes. For more information on raster structure, see Raster.

Selecting Raster Bands and Palettes

To select specific bands and/or palettes, use the RasterSelector prior to the RasterMosaicker.

  • When there are no selected palettes or Merge Palettes is No, each band in a set must have the same band interpretation and Nodata value.
  • When there are selected palettes and Merge Palettes is Yes, each band must have one selected palette, and all palettes must have the same value interpretation.

A variety of options are available for handling alignment issues, overlapping pixel values, Nodata values, and differing resolution.

Attributes from the input features may be merged onto the output raster, and an optional Count attribute will record the number of input features included.

Attributes from the input features may also be appended to an optional list attribute.


Usage Notes

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.