Serializes the geometry of a raster feature into a Blob attribute, encoding the contents according to a choice of common binary raster formats.

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Typical Uses

  • Storing rasters in databases that do not support specific raster types but do support Blobs.
  • Storing a raster as an attribute of a feature, such as attaching images to vector features.

How does it work?

The RasterExtractor receives raster features and puts a copy of the raster geometry into an attribute, as a Blob - a Binary Large OBject.

The Blob content may be encoded as a variety of common raster formats. The name of the chosen format will also be recorded in an attribute for reference when decoding.

There are no parameters in the transformer to control how the raster is formatted, and encoding is done based on default settings for the chosen format. If necessary, format-specific settings may be overwritten by setting format attributes on the raster feature, prior using the RasterExtractor. For example, if encoding to JPEG, the compression level could be set via the jpeg_compression_level format attribute. Consult the appropriate format’s Writer documentation for a complete list of available attributes.

This transformer is unaffected by raster band and palette selection.


Usage Notes

  • This transformer may be used for writing raster data to a database field. Note that when writing the Raster Blob Attribute, you may need to adjust the attribute type to an unbounded data type to avoid truncation of the data. Choose an appropriate attribute type depending on the destination format (for example, an appropriate attribute type for SQL Server is 'image').
  • The RasterReplacer may be used to perform the reverse operation and convert the encoded blob back to the original raster geometry.
  • Different encoding formats may carry through different information. For example, GeoTIFF preserves coordinate system and extents, whereas PNG does not.
  • To carry out a similar operation on vector data, use the GeometryExtractor transformer. For point cloud data, use the PointCloudExtractor.
  • To remove the original geometry after using a RasterExtractor (leaving only the Blob attribute version), use a GeometryRemover.
  • The AttributeFileWriter transformer can be used to write the Raster Blob Attribute directly to a file.

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.