Decodes a binary attribute containing encoded rasters stored as Blobs, replacing the feature’s geometry with the decoded raster.
- Restoring rasters previously extracted into an attribute by the RasterExtractor, often used to store rasters as Blobs in non-spatial databases.
- Creating geometry from rasters read with an AttributeFileReader transformer.
- Extracting images (such as photos) stored as Blobs on a feature.
How does it work?
The RasterReplacer receives features of any geometry type (or no geometry) that have rasters stored as Blob attribute of the feature, most often a result of having previously used the RasterExtractor to store them as Blob attributes to meet format or processing requirements.
The format of the encoded Blob raster must be provided. T
he attribute storing the Blob may be optionally removed after decoding and replacing the feature’s geometry with the raster. Removing the attribute reduces feature size and memory usage, and may improve performance.
Raster band and palette selection are not applicable to this transformer.
In this example, we will retrieve and decode a raster that was previously encoded with a RasterExtractor and loaded to a non-spatial database.
A database reader (PostgreSQL, in this case) reads the feature from the database table, which is then routed into a RasterReplacer.
Examining the feature as it exits the database reader, note that it has no geometry.
The first two attributes - _rasterblob and _rasterformatname - contain the encoded raster as a Blob, and the name of the encoding (GeoTIFF) used for the raster. Both of these attributes were originally created by the RasterExtractor.
In the RasterReplacer’s parameters dialog, Format is set to read the contents of the _rasterformatname attribute. We could alternatively set it explicitly to GeoTIFF, if we did not have an attribute providing that information.
Blob Attribute is set to _rasterblob, and Remove Attribute is set to Yes, which will remove the Blob attribute once it has been decoded and set as the feature’s geometry.
The output feature now has raster geometry, and the Blob attribute has been removed.
- This transformer only works with raster formats. Use the GeometryReplacer for vector formats or the PointCloudReplacer for point cloud formats.
- Different encoding formats may carry through different information. For example, GeoTIFF preserves coordinate system and extents, whereas PNG does not.
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 combing raster with vector data.
For information on raster geometry and properties, see Rasters (IFMERaster).
Working with Rasters
|RasterCellOriginSetter||Sets the cell origin point within cells in a raster.|
Applies a convolution filter (sometimes called a kernel or lens) to raster features and outputs the results.
|RasterExpressionEvaluator||Evaluates expressions on each cell in a raster or pair of rasters, including algebraic operations and conditional statements.|
|RasterExtentsCoercer||Replaces the geometry of input raster features with a polygon covering either the extents of a raster or the extent of data within a raster.|
|RasterGCPExtractor||Extracts Ground Control Point (GCP) coordinate system and point values from a raster feature and exposes them as attributes.|
|RasterGCPSetter||Sets Ground Control Points (GCPs) on a raster, pairing cell positions with known coordinates.|
|RasterGeoreferencer||Georeferences a raster by either known corner coordinates or origin, cell size, and rotation.|
|RasterHillshader||Generates a grayscale shaded relief representation of terrain, based on elevation values.|
Alters the interpretation type of rasters, including all bands, and converts cell values if necessary.
|RasterMosaicker||Merges multiple raster features into a single raster feature.|
|RasterPropertyExtractor||Extracts the geometry properties of a raster feature and exposes them as attributes.|
|RasterPyramider||Resamples rasters to multiple resolutions, based on either number of levels or dimensions of the smallest output raster.|
|RasterResampler||Resamples rasters, based on specified output dimensions, cell size in ground units, or percentage of original, and interpolates new cell values.|
Rotates a raster feature according to its rotation angle property, interpolating new cell values, updating all other affected raster properties, and producing an output raster feature with a rotation angle of zero.
|RasterSubsetter||Clips raster features using pixel bounds instead of ground coordinates, and optionally adds cells around the perimeter.|
|RasterTiler||Splits each input raster into a series of tiles by specifying either a tile size in cells/pixels or the number of tiles.|
|RasterToPolygonCoercer||Creates polygons from input raster features. One polygon is output for each contiguous area of pixels with the same value in the input raster.|
|WebMapTiler||Creates a series of image tiles that can be utilized by web mapping applications such as Bing™ Maps, Google Maps™, or Web Map Tile Service. This is done by resampling rasters to various different resolutions and then splitting them into tiles.|
Working with Bands
|RasterBandAdder||Adds a new band to a raster feature.|
|RasterBandCombiner||Merges coincidental raster features into a single output raster feature, preserving and appending all bands.|
Alters the interpretation type of individual raster bands, converting cell values if necessary.
Removes all unselected bands from a raster feature.
|RasterBandMinMaxExtractor||Extracts the minimum and maximum band values, palette keys, and palette values from a raster feature, and adds them to a list attribute.|
|RasterBandNameSetter||Sets the band name of selected bands on a raster, making raster contents simpler to understand compared to band numbers.|
|RasterBandNodataRemover||Removes the existing nodata identifier from selected bands of a raster feature. Any values previously equal to the nodata value are considered valid data.|
|RasterBandNodataSetter||Sets a new nodata value on selected bands of a raster feature.|
|RasterBandOrderer||Specifies the required order of bands in a raster. Bands are reordered according to the input band indices.|
|RasterBandPropertyExtractor||Extracts the band and palette properties of a raster feature and exposes them as attributes.|
|RasterBandRemover||Removes any selected bands from a raster feature.|
|RasterBandSeparator||Separates bands or unique band and palette combinations, and outputs either individual raster features or a single new raster feature containing all combinations.|
|RasterStatisticsCalculator||Calculates statistics on raster bands and adds the results as attributes.|
Working with Cells
Calculates the aspect (direction of slope) for each cell of a raster. Aspect is measured in degrees from 0 to 360, clockwise from north.
|RasterCellCoercer||Creates individual points or polygons for each cell in a raster, optionally extracting band values as z coordinates or attributes.|
|RasterCellValueCalculator||Evaluates basic arithmetic , minimum, maximum or average operations on the cell values of a pair of rasters.|
|RasterCellValueReplacer||Replaces a range of band values in a raster with a new single value.|
|RasterCellValueRounder||Rounds off raster cell values.|
|RasterSingularCellValueCalculator||Performs basic arithmetic operations on the cell values of a raster against a numeric value.|
|RasterSlopeCalculator||Calculates the slope (maximum rate of change in z) for each cell of a raster.|
Working with Palettes
Creates a palette from an attribute, and adds this palette to all selected bands on a raster.
|RasterPaletteExtractor||Creates a string representation of an existing palette on a raster and saves it to an attribute.|
|RasterPaletteGenerator||Generates a palette out of the selected band(s) of a raster. The output raster will have the selected band(s) replaced by a new band with a palette.|
Alters the interpretation type of raster palettes.
Identifies the palette key that matches a raster band’s nodata value, and sets a value on it.
|RasterPaletteRemover||Removes selected palette(s) from raster features.|
|RasterPaletteResolver||Resolves the palette(s) on a raster by replacing cell values with their corresponding palette values. Palette values with multiple components, such as RGB, are broken down and the individual values assigned to multiple, newly-added bands.|
|RasterCheckpointer||Forces accumulated raster operations to be processed, saving the state to disk and releasing resources to tune performance or assist with memory limitations.|
|RasterConsumer||Reads raster features for testing purposes, including any accumulated raster operations. No additional operations are performed, and nothing is done with the features.|
|RasterExtractor||Serializes the geometry of a raster feature into a Blob attribute, encoding the contents according to a choice of common binary raster formats.|
|RasterNumericCreator||Creates a numeric raster of specified size and resolution, with default cell values.|
|RasterReplacer||Decodes a binary attribute containing encoded rasters stored as Blobs, replacing the feature’s geometry with the decoded raster.|
|RasterRGBCreator||Creates a color raster feature of specified size, resolution, and interpretation type, with default cell values.|
Selects specific bands and palettes of a raster for subsequent transformer operations.
Vectors and Rasters
|ImageRasterizer||Creates a raster representation of vector or point cloud input features, using the fme_color attribute over a solid background fill for vector features. Point clouds may be rendered using their color or intensity components.|
|NumericRasterizer||Creates a numeric raster representation of vector or point cloud input features, where cell values are taken from the z coordinates of the input features and overlaid on a uniform background.|
|MapnikRasterizer||Generates a raster from input vector and raster features, with fine control over symbolization and labeling, using the Mapnik toolkit.|
|PointOnRasterValueExtractor||Extracts the band and palette values from a raster at the location of one or more input points and sets them as attributes on the feature.|
|RasterDEMGenerator||Produces a raster digital elevation model (DEM) by uniformly sampling a Delaunay triangulation generated from input points and breaklines.|
|VectorOnRasterOverlayer||Rasterizes vector or point cloud features onto an existing raster. For vector features the fme_color attribute sets pixel color, and point clouds may be rendered using their color or intensity components.|
Features with rasters stored as attributes.
Features with their geometry replaced by the decoded rasters.
Features without a valid, decodable raster in the specified Blob Attribute will be routed to the <Rejected> port.
Rejected features will have an fme_rejection_code attribute with one of the following values:
Rejected Feature Handling: can be set to either terminate the translation or continue running when it encounters a rejected feature. This setting is available both as a default FME option and as a workspace parameter.
The raster format used to decode the Blob. May be set to an attribute value, or specified explicitly. Choices include:
|Blob Attribute||The attribute from which the blob will be read.|
|Remove Attribute||If Yes, the Blob Attribute will be removed from the output feature.|
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.
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.
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.
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.
Set values depending on one or more test conditions that either pass or fail.
Expressions and strings can include a number of functions, characters, parameters, and more - whether entered directly in a parameter or constructed using one of the editors.
|These functions manipulate and format strings.|
|A set of control characters is available in the Text Editor.|
|Math functions are available in both editors.|
|These operators are available in the Arithmetic Editor.|
|These return primarily feature-specific values.|
|FME and workspace-specific parameters may be used.|
|Working with User Parameters||Create your own editable parameters.|
|FME Licensing Level||FME Professional Edition and above|
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Examples may contain information licensed under the Open Government Licence – Vancouver