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GeoProcessor / Command / RasterizeGeoLayer

Overview

The RasterizeGeoLayer command creates a new raster GeoLayer from a vector GeoLayer using the gdal:rasterize algorithm. See the latest QGIS rasterize documentation. The resulting raster layer is written to an output file specified by the OutputFile parameter or, if not specified, a temporary file with timestamped filename to ensure uniqueness. The GeoTIFF format is used for filenames specified with tif extension and is the default format. The rasterize output file is read as the raster GeoLayer if the GeoLayerID parameter is specified or can be read with the ReadRasterGeoLayerFromFile command.

The rasterization occurs using one of the following approaches:

  1. RasterUnits=GeoUnits:
    • output units will be the units of the input vector layer, for example degrees if geographic coordinates
    • specify CellWidth and CellHeight parameters as the cell dimensions, where the values will be in the input layer's geographic units (e.g., degrees)
  2. RasterUnits=Pixel:
    • output units will be pixels, such as for an image
    • specify RasterWidth and RasterHeight parameters as the total width and height of the image, in pixels

The underlying software may retain a lock on the file. The RasterizeGeoLayer command attempts to remove the output file before running (to ensure that output is current) and will warn if unsuccessful. This typically means that another program is using the file. This issue should be fixed by the user because otherwise the old output may mistakenly be assumed to be current output.

The RasterizeGeoLayer command also attempts to delete temporary files after reading (to avoid filling up the disk). If unsuccessful, typically because underlying software has a lock on the file, a warning will be logged to the log file and the file will remain. The file is added to the list of files to be removed, which will be processed when the GeoProcessor is next started.

Command Editor

The following dialog is used to edit the command and illustrates the command syntax when using an automatically-generated temporary filename and reading into a GeoLayer.

RasterizeGeoLayer-GeoLayerID

RasterizeGeoLayer-GeoLayerID Command Editor when Reading a GeoLayer (see full-size image)

The following illustrates the command syntax when specifying the output file and not reading a GeoLayer. A ReadRasterLayerFromFile command can be used to read the file.

RasterizeGeoLayer-OutputFile

RasterizeGeoLayer-OutputFile Command Editor when Not Reading a GeoLayer (see full-size image)

Command Syntax

The command syntax is as follows:

RasterizeGeoLayer(Parameter="Value",...)

Command Parameters

Parameter                              Description Default                
GeoLayerID
required		 The vector GeoLayer identifier. ${Property} syntax is recognized. None - must be specified.
Attribute The attribute name that indicates values to be assigned in the raster layer. Attribute or ConstantValue must be specified.
OutputFile The output raster file (relative or absolute path). ${Property} syntax is recognized. Write to a temporary file.
RasterFormat Format of the raster file that is created during processing:
  • GeoTIFF
 GeoTIFF
CellValueType Type for the cell values:
  • Byte - byte
  • Integer16 - 16-bit integer
  • Integer32 - 32-bit integer
  • Float32 - 32-bit floating point number
  • Float64 - 64-bit floating point number
 Byte
RasterUnits Data units for raster layer:
  • GeoUnits - geographic units defined by the coordinate system (used for rasters with data)
  • Pixels - pixels (used for images)
 None - must be specified.
RasterWidth If RasterUnits=Pixels, the width of the image in pixels.
RasterHeight If RasterUnits=Pixels, the height of the image in pixels.
CellWidth If RasterUnits=GeoUnits, the width of a cell in raster units.
CellHeight If RasterUnits=GeoUnits, the height of a cell in raster units.
ConstantValue Constant value to assign to the raster rather than using Attribute value.
MissingValue Value to use for missing or "no data" value. This indicates in the raster layer the attribute value that is used for missing values.
NewGeoLayerID GeoLayer identifier for the new raster layer. Formatting characters and ${Property} syntax is recognized. Refer to GeoLayerID documentation for best practices on GeoLayer identifiers. Create the raster layer file but don't read the layer.
IfGeoLayerIDExists The action that occurs if the GeoLayerID already exists within the GeoProcessor:
  • Replace - The existing GeoLayer within the GeoProcessor is replaced with the new GeoLayer. No warning is logged.
  • ReplaceAndWarn - The existing GeoLayer within the GeoProcessor is replaced with the new GeoLayer. A warning is logged.
  • Warn - The new GeoLayer is not created. A warning is logged.
  • Fail - The new GeoLayer is not created. A fail message is logged.
 Replace

Examples

See the automated tests.

Troubleshooting

See Also