Applies a convolution filter (sometimes called a kernel or lens) to raster features and outputs the results.

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Typical Uses

  • Image manipulation
  • Raster data analysis
  • Smoothing, blurring, or sharpening an image
  • Edge detection
  • Reducing image “noise” (to help with future feature detection)
  • Calculate slopes in a raster DEM

How does it work?

The RasterConvolver receives raster features and applies convolution filters to them, then outputs the modified rasters.

Convolution is a mathematical operation carried out on two objects in order to create a third. In this transformer, the first object is a raster feature and the second object is a raster-like matrix of numbers. The operation can be one of many common mathematical operations.

Processing the raster feature against the matrix, using the specified operator, returns a new raster feature with new qualities. Such filtering is used for smoothing, sharpening, enhancing edges and other raster image manipulation operations.

Convolution filters are defined by a kernel (specified by a matrix of weights) and a mathematical operation. The filter is applied, in turn, to each of the cells of the input raster. Each cell is given a new value according to the result of the mathematical operation on the cell and its neighbors, using the matrix of weights.

A selection of predefined Convolution Filters is available, and kernels may be modified or completely user-defined. Options are available for edge and Nodata handling.

This transformer supports raster band selection. The RasterSelector can be used to modify the selection. Palettes are not supported.


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
Aliases RasterLensProcessor

FME Community

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