TopographicShadingUsingRGB Task

This task blends an RGB (red/green/blue) color representation of a digital elevation model (DEM) with a topographic feature (typically, shaded relief). The result is a color image that provides a better visual appearance of the shape and texture of topographic features than using the DEM alone.

Example

; Start the application

e = ENVI()

; Open an input file

File = Filepath('bhdemsub.img', $

Subdir=['classic', 'data'], $

Root_Dir=e.Root_Dir)

Raster = e.OpenRaster(File)

; Run the GetColorTable task

ColorTask = ENVITask('GetColorTable')

ColorTask.COLOR_TABLE_NAME = 'Hue Sat Lightness 2'

ColorTask.Execute

; Set the DEM stretch parameters

DEMStretch = ENVIStretchParameters( $

STRETCH_TYPE='Square Root', $

MIN_VALUE=1241, $

MAX_VALUE=1503)

; Set the topographic stretch parameters

TopoStretch = ENVIStretchParameters( $

STRETCH_TYPE='Linear', $

MIN_VALUE=0.73, $

MAX_VALUE=0.88)

; Get the topographic shading task from the catalog of ENVITasks

Task = ENVITask('TopographicShadingUsingRGB')

; Define inputs

Task.INPUT_RASTER = Raster

Task.DEM_STRETCH = DEMStretch

Task.DEM_COLOR_TABLE = ColorTask.OUTPUT_COLOR_TABLE

Task.TOPOGRAPHIC_PRODUCT = 'Shaded Relief'

Task.TOPOGRAPHIC_STRETCH = TopoStretch

Task.BLEND_PERCENT = 60

Task.KERNEL_SIZE = 5

; Run the task

Task.Execute

; Get the collection of data objects currently available in the Data Manager

DataColl = e.Data

; Add the output to the Data Manager

DataColl.Add, Task.OUTPUT_RASTER

; Display the result

View = e.GetView()

Layer = View.CreateLayer(Task.OUTPUT_RASTER)

Syntax

Result = ENVITask('TopographicShadingUsingRGB')

Input properties (Set, Get): AZIMUTH, BLEND_PERCENT, DEM_COLOR_TABLE, DEM_STRETCH, ELEVATION, INPUT_RASTER, KERNEL_SIZE, OUTPUT_RASTER_URI, TOPOGRAPHIC_PRODUCT, TOPOGRAPHIC_STRETCH

Output properties (Get only): OUTPUT_RASTER

Properties marked as "Set" are those that you can set to specific values. You can also retrieve their current values any time. Properties marked as "Get" are those whose values you can retrieve but not set.

Methods

This task inherits the following methods from ENVITask:

Properties

This task inherits the following properties from ENVITask:

COMMUTE_ON_DOWNSAMPLE

AZIMUTH (optional)

Specify the azimuth angle of the model in degrees. The value will only be used for the Shaded Relief product. The default value is 45.0.

BLEND_PERCENT (optional)

Specify the percentage of blending between the input raster and topographic feature. The default value is 50.0.

DEM_COLOR_TABLE (required)

Specify a color table to apply to the input raster. This property only acccepts a [*, 3] array of color table values. To use a predefined color table, you can run the GetColorTable task, then pass the resulting array to DEM_COLOR_TABLE.

DEM_STRETCH (required)

Specify an ENVIStretchParameters object with the stretch to apply to the input raster before applying a color table.

ELEVATION (optional)

Specify the elevation angle of the model in degrees. The value will only be used for the Shaded Relief product. The default value is 45.0.

INPUT_RASTER (required)

Specify a raster on which to perform topographic shading; for example, a DEM, gridded bathymetry data, or gridded magnetic anomaly data.

KERNEL_SIZE (optional)

Specify the size of the kernel used for topographic processing. The default value is 3.

OUTPUT_RASTER

This is a reference to the output raster of filetype ENVI.

OUTPUT_RASTER_URI (optional)

Specify a string with the fully qualified filename and path of the associated OUTPUT_RASTER. If you do not specify this property, or set it to an exclamation symbol (!), a temporary file will be created.

TOPOGRAPHIC_PRODUCT (optional)

Specify a string with the topographic product to calculate. The choices are as follows:

Slope
Aspect
Shaded Relief (default)
Profile Convexity
Plan Convexity
Longitudinal Convexity
Cross Sectional Convexity
Minimum Curvature
Maximum Curvature
RMS
Slope Percent

See Background for descriptions of the options.

TOPOGRAPHIC_STRETCH (required)

Specify an ENVIStretchParameters object with the stretch to apply to the selected topographic product before blending.

Version History

ENVI 5.5. 1

Introduced

API Version

4.2