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RasterMosaicker

Merges multiple raster features into a single raster feature.

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 Rasters (IFMERaster).

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.

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.

Raster Transformers

Working with Rasters

These transformers generally apply to whole rasters.

RasterCellOriginSetter	Sets the raster's cell origin.
RasterConvolver	Accepts input features containing a raster geometry and outputs the features after applying a convolution filter to all the bands. Convolution filters are applied using a kernel, specified by a matrix of weights for the neighboring values, over all the cells of an input raster geometry. Such filtering is used for smoothing, sharpening, enhancing edges and other raster image manipulation operations.
RasterExpressionEvaluator	Evaluates expressions on each cell in a raster, such as algebraic operations or conditional statements.
RasterExtentsCoercer	Replaces the geometry of input raster features with a polygon covering the extents of the raster.
RasterGCPExtractor	Extracts the coordinate system and the Ground Control Points (GCP) from the raster feature and exposes them as attributes.
RasterGCPSetter	Sets the Ground Control Points (GCP) on a raster with the specified Column (pixel), Row (line), X Coordinate, Y Coordinate and Z Coordinate.
RasterGeoreferencer	Georeferences a raster using the specified parameters.
RasterHillshader	Generates a shaded relief effect, useful for visualizing terrain.
RasterInterpretationCoercer	Alters the underlying interpretation of the bands of the raster geometry on the input features, using the specified conversion options. For example, an input raster feature with three bands of interpretation (UInt16, Gray8, and Real64) could be converted to a raster feature with three bands of interpretation (Red8, Green8, and Blue8) or four bands of interpretation (Red16, Green16, Blue16, and Alpha16) in a single operation.
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	Creates a series of pyramid levels for each input raster feature by specifying either the smallest pyramid level size or the number of pyramid levels to generate. Pyramid levels are created by resampling input rasters to various different resolutions.
RasterResampler	Resamples an input raster using the desired dimensions, the desired cell size in ground units, or a percentage of the size.
RasterRotationApplier	Applies the raster rotation angle on the input raster properties to the rest of the raster properties and data values. The expected input is a raster with a non-zero rotation angle and the expected output is a rotated raster with a rotation angle of 0.0. It is expected that the input raster properties will be modified to conform the output raster properties for a raster rotated by the given angle. Applying a rotation angle is primarily done for compatibility with other processing and writers that cannot handle a rotation angle.
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. The added band will have the same value in all cells, and the same raster-level properties as other bands in the raster (that is, number of rows/columns, cell spacing, cell origin, and so on).
RasterBandCombiner	Merges multiple overlapping raster features into a single raster feature. It accepts a number of input raster features, each of which has one or more bands. The bands are removed from the input features and appended to a single output raster feature.
RasterBandInterpretationCoercer	Alters the underlying interpretation of the selected bands of the raster geometry on the input features, using the specified conversion options. For example, an input raster feature with a single band of interpretation UInt8 could be converted to a single band of Gray8 or UInt16 data.
RasterBandKeeper	Removes all bands of a raster, except for those that are selected. The RasterSelector can be used to modify the selection. If all bands in the source raster are selected, the raster will remain unchanged.
RasterBandMinMaxExtractor	Extracts the band minimum and maximum values, palette minimum and maximum keys and palette minimum and maximum values of a raster feature and exposes them as attributes.
RasterBandNameSetter	Sets the name of selected bands on a raster.
RasterBandNodataRemover	Removes the existing nodata identifier from the selected bands of a raster feature. That is, any values that were previously equal to the nodata value will now be considered valid data.
RasterBandNodataSetter	Identifies a value to act as a nodata identifier on a raster feature at the band level. That is, values equal to the specified value will now be considered invalid, and will not be affected by many operations (for example, offsetting or scaling).
RasterBandOrderer	Specifies the 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 the selected band(s) of a raster. To modify the selection, see the RasterSelector.
RasterBandSeparator	Separates the bands and palettes from each input raster feature into one or more output raster features based on the number of input bands and palettes.
RasterStatisticsCalculator	Calculates statistics on raster bands and exposes them as attributes. Bands with palettes are valid.

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, starting clockwise from the north. Each selected input band will be converted to a Real64 band with output values that represent the aspect. If an input band does not have a nodata value, the output band nodata value will be set to -1.
RasterCellCoercer	Decomposes all input numeric raster features into individual points or polygons. One vector feature is output for each cell in the band.
RasterCellValueCalculator	Performs an arithmetic operation on a pair of rasters.
RasterCellValueReplacer	Replaces a range of values in the source raster with a new single value.
RasterCellValueRounder	Rounds off raster cell values.
RasterSingularCellValueCalculator	Performs an arithmetic operation on two operands: the cell values of a raster and 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. Selected bands are required to have an interpretation of UINT8, UINT16, or UINT32. Note that palette entries will be discarded if they do not fit within the interpretation of a selected band. For example, when adding a palette to a UINT8 band, all keys that are greater than 255 will be dropped.
RasterPaletteExtractor	Creates a string representation of an existing palette 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 underlying interpretation of the palettes of the raster geometry on the input features, using the specified conversion options. For example, an input raster feature with a single band with a single palette of interpretation RGB24 could be converted to a single band with a single palette of RGB64 or String data.
RasterPaletteNodataSetter	Identifies the nodata value on a raster feature at the palette level. The transformer will succeed in setting the specified nodata value only if the input raster band(s) have at least one palette and a nodata key has already been set on the band.
RasterPaletteRemover	Removes the selected palette(s) of a raster. The palette's band retains the palette key, but the corresponding values are lost.
RasterPaletteResolver	Resolves the palettes of the selected bands of the input raster features by using the band cell values to look up the corresponding palette values, which then replace the original band cell values in the raster.

Workflow Control

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

RasterCheckpointer	Sets a checkpoint in the raster processing which forces previous processing to occur immediately. Once complete, it saves the current state to disk.
RasterConsumer	Requests the tile(s) from the raster geometry but no actual operations are performed on the tile(s).
RasterExtractor	Serializes the geometry of the feature into the Blob Attribute based on the selected writer format.
RasterNumericCreator	Creates a feature with a raster of the specified size with a numeric value and sends it into the workspace for processing. It is useful for creating a very large image with a user-specified width and height.
RasterReplacer	Replaces the geometry of the feature with the geometry held in the Blob Attribute. The blob is decoded according to the selected raster format.
RasterRGBCreator	Creates a feature with a raster of the specified size with an RGB value and sends it into the workspace for processing.
RasterSelector	Selects specific bands and palettes of a raster for subsequent transformer operations. The bands and palettes are selected using the band and palette indices, specified in a string. The string may either be specified explicitly or through an attribute. The format of the string is B P (separated with a space), where B is the band index and P is the palette index of the band and palette to be operated on. Indices are zero-based, so the first band or palette is at index 0.

Vectors and Rasters

These transformers generally involve using rasters and vector data together.

ImageRasterizer	Draws input point, line and polygon features onto a color raster filled with the background color. The fme_color attribute of the input vector features is used to generate pixel values. Features without an fme_color attribute will be discarded.
NumericRasterizer	Draws input point, line and polygon features onto a numeric raster filled with the background value. The Z coordinates of the input vector features are used to generate pixel values. Features without Z coordinates will be discarded.
MapnikRasterizer	Draws input point, line, polygon, and raster features onto a raster using the Mapnik toolkit.
PointOnRasterValueExtractor	Extracts the band and palette values from a raster at the location of each input point and sets them as attributes on the feature.
VectorOnRasterOverlayer	Overlays vector features onto a single raster feature by drawing them onto the resulting output raster. The properties of the output raster are identical to that of the input raster.

Configuration

Input Ports

Output Ports

Parameters

Transformer

Group By

The rasters may be organized into groups with the Group By parameter, with each group of rasters having its own output raster.

Parallel Processing

Select a level of parallel processing to apply. Default is No Parallelism.

Parallel Processing

Note: How parallel processing works with FME: see About Parallel Processing for detailed information.

This parameter determines whether or not the transformer should perform the work across parallel processes. If it is enabled, a process will be launched for each group specified by the Group By parameter.

Parallel Processing Levels

Parameter	Number of Processes
No Parallelism	1
Minimal	coresThe processor, or CPU, is the physical part of the computer that performs mathematical calculations. It is the most important part of a computer system. Traditional processors have only one core on the processor, meaning that at any given time, only one set of calculations is being performed. If a processor is dual-core, this means the single chip contains hardware for two processors, now called cores to distinguish them from the single chip, running simultaneously, side by side. (Source: http://www.ehow.com/facts_5730257_computer-core-processors_.html) / 2
Moderate	exact number of cores
Aggressive	cores x 1.5
Extreme	cores x 2

For example, on a quad-core machine, minimal parallelism will result in two simultaneous FME processes. Extreme parallelism on an 8-core machine would result in 16 simultaneous processes.

You can experiment with this feature and view the information in the Windows Task Manager and the Workbench Log window.

Input Ordered

No: This is the default behavior. Processing will only occur in this transformer once all input is present.

By Group: This transformer will process input groups in order. Changes of the value of the Group By parameter on the input stream will trigger batch processing on the currently accumulating group. This will improve overall speed if groups are large/complex, but could cause undesired behavior if input groups are not truly ordered. Specifically, on a two input-port transformer, "in order" means that an entire group must reach both ports before the next group reaches either port, for the transformer to work as expected. This may take careful consideration in a workspace, and should not be confused with both port's input streams being ordered individually, but not synchronously.

Considerations for Using Input is Ordered By

Using Ordered input can provide performance gains in some scenarios, however, it is not always preferable, or even possible. Consider the following when using it, with both one- and two-input transformers.

Single Datasets/Feature Types: Are generally the optimal candidates for Ordered processing. If you know that the dataset is correctly ordered by the Group By attribute, using Input is Ordered By can improve performance, depending on the size and complexity of the data.

If the input is coming from a database, using ORDER BY in a SQL statement to have the database pre-order the data can be an extremely effective way to improve performance. Consider using a Database Readers with a SQL statement, or the SQLCreator transformer.

Multiple Datasets/Feature Types: Since all features matching a Group By value need to arrive before any features (of any feature type or dataset) belonging to the next group, using Ordering with multiple feature types is more complicated than processing a single feature type.

Multiple feature types and features from multiple datasets will not generally naturally occur in the correct order.

One approach is to send all features through a Sorter, sorting on the expected Group By attribute. The Sorter is a feature-holding transformer, collecting all input features, performing the sort, and then releasing them all. They can then be sent through an appropriate filter (TestFilter, AttributeFilter, GeometryFilter, or others), which are not feature-holding, and will release the features one at a time to the transformer using Input is Ordered By, now in the expected order.

The processing overhead of sorting and filtering may negate the performance gains you will get from using Input is Ordered By. In this case, using Group By without using Input is Ordered By may be the equivalent and simpler approach.

In all cases when using Input is Ordered By, if you are not sure that the incoming features are properly ordered, they should be sorted (if a single feature type), or sorted and then filtered (for more than one feature or geometry type).

As with many scenarios, testing different approaches in your workspace with your data is the only definitive way to identify performance gains.

Alignment

Snapping Type

Used if the rasters are not perfectly aligned. The first input feature defines the reference grid.

Resample: Resamples (if necessary) subsequent raster features to fit the reference grid.

Offset: Moves (if necessary) subsequent raster features to fit the reference grid, without resampling. Offsetting may be faster than resampling, but requires that all rasters have the same pixel size.

Interpolation Type

If the input rasters do not line up exactly or if they have different spacings, this transformer will use the selected Interpolation Type to snap and/or resample the input rasters according to the selected method:

Nearest Neighbor	The simplest and fastest method. Values are copied from the nearest cell.
Bilinear	Calculates a weighted average, adjusted for distance, from the four (4) nearest cells.
Bicubic	Calculates a weighted average, adjusted for distance, from the sixteen (16) nearest cells.
Average 4	Calculates a simple average from the four (4) nearest cells. Similar to Bilinear and is useful for numeric rasters such as DEMs.
Average 16	Calculates a simple average from the sixteen (16) nearest cells. Similar to Bicubic and is useful for numeric rasters such as DEMs.

Data Values

Overlapping Values

Specifies how output cell values will be calculated when rasters overlap.

Last	The last value. That is, the last raster that overlaps a cell will set the value for that cell. Note that this means the order of the input features may be important. You can use a Sorter transformer to enforce the order in which features are processed.
Minimum	The minimum value.
Maximum	The maximum value.
Average	The average of all values.
Sum	The sum of all values.
Composite Using Alpha Band	Values will be blended based on the alpha band. If this option is selected, all input rasters must have exactly one alpha band, and the values from these alpha bands will be used to blend all the other bands' values in areas where overlap occurs, effectively achieving transparency. An alpha value of 0 means complete transparency, and an alpha value of 1 means complete opacity.

Note that the Average, Sum, and Composite Using Alpha Band options are not compatible with palettes.
When all values for a cell are nodata, the output value will be nodata.

Nodata Overwrites Data

When Overlapping Values is set to Last, this option specifies whether nodata values should overwrite data values in rasters that have been previously drawn.

Yes: any nodata overlapping real data values will overwrite the real data values.

No: nodata overlapping real data will be ignored, and the real data values will be preserved. Note that data values will always overwrite both nodata and data values.

Attributes

Accumulation Mode

Drop Incoming Attributes: Attributes from all incoming features are removed, including the first feature.

Merge Incoming Attributes: Attributes from incoming features are merged onto the output raster feature.

Use Attributes from One Feature: Attributes from the first input raster feature are retained.

Count Attribute

If a Count Attribute is given, then an attribute with this name will be added to each output feature, containing the number of features that were combined to create the raster feature.

Generate List

When enabled, adds a list attribute to the output raster feature, retaining attribute values for each input feature.

List Name

Enter a name for the list attribute.

Note: List attributes are not accessible from the output schema in Workbench unless they are first processed using a transformer that operates on them, such as ListExploder or ListConcatenator. All list attribute transformers are displayed in the Contents pane of the Transformer Help under Lists. Alternatively, AttributeExposer can be used.

Add To List

All Attributes: All attributes will be added to the output raster feature.

Selected Attributes: Enables the Selected Attributes parameter, where specific attributes may be chosen to be added.

Selected Attributes

Enabled when Add To List is set to Selected Attributes. Specify the attributes you wish to be added.

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

Processing Behavior	Group-Based
Feature Holding	Yes
Dependencies	None
FME Licensing Level	FME Professional Edition and above
Aliases
History
Categories	Filters and Joins Rasters

FME Knowledge Center

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