RasterInterpretationCoercer

Alters the interpretation type of rasters, including all bands, and converts cell values if necessary.

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Typical Uses

• Changing raster interpretation type to meet format or processing requirements.

How does it work?

The RasterInterpretationCoercer receives raster features and converts all bands based on a chosen Destination Interpretation Type. Choices include:

• RGB24
• RGBA32
• RGB48
• RGBA64
• Gray8
• Gray16
• Red8
• Red16
• Green8
• Green16
• Blue8
• Blue16
• Alpha8
• Alpha16
• UInt8
• Int8
• UInt16
• Int16
• UInt32
• Int32
• UInt64
• Int64
• Real32
• Real64

Options are available to control the manner in which cell values are converted, handling color to color, numeric to color, color to numeric, numeric to numeric, and floating point to integer conversions.

Band names, if they exist, are retained.

This transformer is unaffected by raster band and palette selection.

Multi-Band Rasters

When converting to an interpretation with multiple components, such as RGB and RGBA, the input raster will be expected to have exactly 1, 3, or 4 bands. If only one band is supplied, it will be cloned to create the correct number of bands for conversion to the chosen interpretation.

When converting to a single color or numeric interpretation, multiple input bands will be averaged into a single one.

Palettes

If bands selected for conversion contain palettes, the destination interpretation must be an unsigned integer - UInt8, UInt16 or UInt32 to accommodate the palette keys.

Example: Converting an RGB48 raster to RGBA32

In this example, we want to reduce the bit depth and add an alpha band to our original raster, an RGB48 image that has three 16-bit bands - red, green, and blue.

Note the individual cell values for the three bands, which fall in the range of 0 to 65535 (the possible values for a 16-bit band).

The raster is routed into a RasterInterpretationCoercer.

In the parameters dialog, we select a Destination Interpretation of RGBA32.

This choice enables a number of Conversion Options. The transformer is not aware of what type of values it may need to convert, and so provides options for all variations - color, numeric, and float.

For our RGB input raster, the important ones are:

• RGB to RGBA: Create opaque alpha band. This will add an alpha band, and all cells in the band will have the maximum value for the selected bit depth - in this case, 255, as we are converting to 8-bit bands.
  The input raster does not have nodata values, and so we cannot create an alpha band from them.
• Convert from Color to Color: Scale by data type. Values will be scaled according to the ranges of both the input and output rasters. As we are converting from 16-bit to 8-bit, this means that:
  • 0 will become 0
  • 65535 (the maximum 16-bit value) becomes 255 (the maximum 8-bit value)
  • Values in between are scaled accordingly.

The output raster feature has four bands, including the new alpha band, and all are 8-bit.

The individual cell values have been scaled, and the alpha values are set to 255 (fully opaque).

Note that reducing bit depth may result in a loss of precision. Conversely, increasing bit depth will not increase image quality.

Usage Notes

• The RasterBandInterpretationCoercer performs similar conversions on individual bands.
• The RasterPaletteInterpretationCoercer performs similar conversions on palettes.

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).

Raster Transformers

Working with Rasters

These transformers generally apply to whole rasters.

RasterCellOriginSetter	Sets the cell origin point within cells in a raster.
RasterConvolver	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.
RasterInterpretationCoercer	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.
RasterRotationApplier	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

These transformers generally apply to 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.
RasterBandInterpretationCoercer	Alters the interpretation type of individual raster bands, converting cell values if necessary.
RasterBandKeeper	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

These transformers generally apply to individual cells.

RasterAspectCalculator	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

These transformers generally apply to palettes.

RasterPaletteAdder	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.
RasterPaletteInterpretationCoercer	Alters the interpretation type of raster palettes.
RasterPaletteNodataSetter	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.

Workflow Control

These transformers generally control the flow of features in a workspace.

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.
RasterSelector	Selects specific bands and palettes of a raster for subsequent transformer operations.

Vectors and Rasters

These transformers generally involve using rasters and vector data together.

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.

Configuration

Input Ports

Input

This transformer accepts only raster features.

Output Ports

Output

Raster features with interpretation type modified and values converted as specified.

<Rejected>

Non-raster features will be routed to the <Rejected> port, as well as invalid rasters.

Rejected features will have an fme_rejection_code attribute with one of the following values:

INVALID_GEOMETRY_TYPE
INVALID_RASTER_NO_BANDS

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.

Parameters

Interpretation

Destination Interpretation Type

Select the destination interpretation along with the bit depth. Different interpretations allow for different conversion options to be used. If any bands on the raster contain palettes, then the destination interpretation is restricted to UInt8, UInt16 or UInt32.

Conversion Options

RGBA to RGB	Select the action to perform when converting four bands representing an RGBA raster to three bands representing an RGB raster. Drop the alpha band: Discards the alpha band. Apply the alpha band: Multiplies all RGB values with their corresponding, normalized alpha value.
RGB to RGBA	Select the action to perform when converting three bands representing an RGB raster to four bands representing an RGBA raster. Create opaque alpha band: Adds a new alpha band which has the maximum value for the data type in all cells. Create alpha band from nodata: Creates a new band which has the maximum value for the data type only in data cells. A cell is considered to be nodata when, for each selected band, the value for that cell is equal to that band's nodata value. If any cell value is not equal to that band's nodata value, the cell will be considered data. Note that when this option is selected, it is required that all input bands have a nodata value.
Convert from Color to Color Convert from Numeric to Color Convert from Color to Numeric Convert from Numeric to Numeric	Select the action to undertake when the given conversion between different types or different bit depths occurs. Cast* Converts values to the chosen type, without validation. If values fall outside the range of the destination type, unexpected results may occur. Bounded cast* Converts values to the chosen type, and validates that the source values fit into the destination type, effectively preventing underflow and overflow. If a source value does not fit, the corresponding destination value will either be set to its type's minimum or maximum value as appropriate. Scale by data values Finds the minimum and maximum values of the source values and uses them to scale the values to the full range of the destination type. Scale by data type Scales the source values while preserving all proportions in regard to the source and destination types' range. * Note: Cast and Bounded Cast use C-style casts.
Convert from Float to Integer	Specifies the action to perform when converting from a floating-point value to an integer. Round Rounds to floating-point value to the nearest integer. Ceiling Gets the next integer which is greater than or equal to the floating-point value. Floor Gets the next integer which is less than or equal to the floating-point value.

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.

How to Set Parameter Values

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.

Text Editor

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.

Arithmetic Editor

Conditional Values

Set values depending on one or more test conditions that either pass or fail.

Parameter Condition Definition Dialog

Content

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.

Content Types

String Functions	These functions manipulate and format strings.
Special Characters	A set of control characters is available in the Text Editor.
Math Functions	Math functions are available in both editors.
Math Operators	These operators are available in the Arithmetic Editor.
FME Feature Functions	These return primarily feature-specific values.
FME Parameters	FME and workspace-specific parameters may be used.
Working with User Parameters	Create your own editable parameters.

Reference

Related Transformers

RasterBandInterpretationCoercer

RasterPaletteInterpretationCoercer

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Examples may contain information licensed under the Open Government Licence – Vancouver