LogStretchRaster Task
This task accepts a source raster and returns a raster with a logarithmic stretch applied. This is a non-linear stretch where the low-range brightness is enhanced. The logarithmic stretch is useful for enhancing features lying in the darker parts of the original image.
The virtual raster associated with this task is ENVILogStretchRaster.
Example
; Start the application
e = ENVI()
; Open an input file
File = Filepath('qb_boulder_msi', Subdir=['data'], $
Root_Dir=e.Root_Dir)
Raster = e.OpenRaster(File)
; Get the task from the catalog of ENVITasks
Task = ENVITask('LogStretchRaster')
; Define inputs
Task.INPUT_RASTER = Raster
Task.MIN = [180, 210, 120, 90]
Task.MAX = [800, 1300, 1055, 1100]
; 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('LogStretchRaster')
Input properties (Set, Get): BRIGHTNESS, INPUT_RASTER, MAX, MIN, OUTPUT_RASTER_URI
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:
This task also contains the following properties:
BRIGHTNESS (optional)
Set this property to an integer value from 0 to 100, indicating the brightness level to display. The default value is 50 if no brightness is specified. You can also set this value to a scalar or an array with the same number of elements as the raster has bands.
INPUT_RASTER (required)
Specify a raster on which to apply the stretch.
MAX (required)
Set this property to the maximum value to be considered, also known as the "white point." If the value is a scalar, it applies to all bands. If it is an array, it must have the same number of elements as the input raster has bands.
MIN (required)
Set this property to the minimum value to be considered, also known as the "black point." If this value is a scalar, it applies to all bands. If it is an array, it must have the same number of elements as the input raster has bands.
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 to export the associated OUTPUT_RASTER.
- If you set this property to an asterisk symbol (*), the output raster will be virtual and not written to disk.
- If you do not specify this property, or set it to an exclamation symbol (!), a temporary file will be created.
Version History
|
ENVI 5.2 |
Introduced |
|
ENVI 5.5 |
OUTPUT_RASTER_URI now supports '*', which allows OUTPUT_RASTER to be virtual output. |
API Version
4.2