Use this procedure to build an FFT filter image.

Example

; Start ENVI
e = ENVI()
 
; Create an FFT filter image
ENVI_Doit, 'ENVI_Filter_Doit', $
   NS = 512L, $
   NL = 512L, $
   RADIUS = [60,150], $
   NBP = 0, $
   FILTER = 2, $
   OUT_NAME = 'TestFilter.dat'
 
; Create a view
View = e.GetView()

When processing is complete, select Linear 5% from the Stretch Type drop-down list in the ENVI toolbar.

Syntax

ENVI_DOIT, 'ENVI_FILTER_DOIT' [, ANN_NAME=string], FILTER={0 | 1 | 2 | 3 | 4 | 5}, /IN_MEMORY, NBP=integer, NL=integer, NS=integer, OUT_NAME=string, R_FID=variable, RADIUS=array

Keywords

ANN_NAME (optional)

Use this keyword to specify an annotation filename for user-defined filters. This keyword is not used for circular or band-pass filters.

FILTER

Use this keyword to specify an integer corresponding to the filter type to build. Choose one of the following:

  • 0: Circular pass filter
  • 1: Circular cut filter
  • 2: Band pass filter
  • 3: Band cut filter
  • 4: User-defined pass filter
  • 5: User-defined cut filter

IN_MEMORY

Set this keyword to specify that output should be stored in memory. If you do not set IN_MEMORY, output will be stored on disk and you must specify OUT_NAME (see below).

NBP

Use this keyword to specify the number of border pixels for the filter transitions.

NS

Use this keyword to specify the number of samples in the output filter image.

NL

Use this keyword to specify the number of lines in the output filter image.

OUT_NAME

R_FID

RADIUS

For circular filters, this keyword specifies the filter radius in pixels. For band-pass filters, this keyword is a two-element array of integers specifying the inner and outer filter radius in pixels. This keyword is not used for user-defined filters.

API Version

4.2