This routine is obsolete and has been replaced by the following tasks: AdditiveLeeAdaptiveFilter, AdditiveMultiplicativeLeeAdaptiveFilter, BitErrorAdaptiveFilter, EnhancedFrostAdaptiveFilter, EnhancedLeeAdaptiveFilter, FrostAdaptiveFilter, GammaAdaptiveFilter, KuanAdaptiveFilter, LocalSigmaAdaptiveFilter, and MultiplicativeLeeAdaptiveFilter.

Use this procedure to apply an adaptive filter, including the Lee filter, localized sigma filter, and bit error removal.

Example

The following example applies a Lee filter to an image. It displays the filtered image inside a Standard Portal on top of the original image.

; Start ENVI
e = ENVI()
 
; Open a data file
File = Filepath('qb_boulder_msi', Root_Dir = e.Root_Dir, $
   Subdir = ['data'])
Raster = e.OpenRaster(File)
 
; Determine an output file
OutFile = e.GetTemporaryFilename()
 
; Return a file ID
fid = ENVIRasterToFID(Raster)
 
; Perform adaptive filtering. 
ENVI_File_Query, fid, DIMS=dims, NB=nb
ENVI_Doit,'Adapt_Filt_Doit', $
   FID = fid, $
   DIMS = dims, $
   POS = Lindgen(nb), $
   KX = 5, $
   SIGMA = 0.5, $
   METHOD = 0, $
   MULT_MEAN = 1, $
   NOISE_TYPE = 1, $
   OUT_NAME = OutFile, $
   R_FID = r_fid
 
; Pass the R_FID to an ENVIRaster object.
OutRaster = ENVIFIDToRaster(r_fid)
 
; Display the original data and the result
View = e.GetView()
Layer = View.CreateLayer(Raster)
Portal = View.CreatePortal()

Syntax

ENVI_DOIT, 'ADAPT_FILT_DOIT', ADD_MEAN=floating point, [, CMAX=floating point] [, CU=floating point], DAMP=floating point, DIMS=array, FID=file ID, /IN_MEMORY, KX=integer, METHOD={0 | 1 | 2 | 3 | 4 | 5 | 6 | 7}, MULT_MEAN=floating point, NLOOK=integer, NOISE_TYPE={0 | 1 | 2}, OUT_BNAME=string array, OUT_NAME=string, POS=array, R_FID=variable, /REPLACE, SIGMA=value, TOL=value, VMAX=value, VMIN=value

Keywords

ADD_MEAN

Use this keyword to specify a variable that contains the additive noise mean. ADD_MEAN is a floating-point number. Use this keyword only when using the Lee filter (METHOD=0) and when NOISE_TYPE=2.

CMAX (optional)

Use this keyword only when using the Enhanced Lee filter (METHOD=6) or Enhanced Frost (METHOD=7). Set this keyword to a floating-point value that represents the coefficient of variation cutoff for heterogeneous areas.

CU (optional)

Use this keyword only when using the Enhanced Lee filter (METHOD=6) or Enhanced Frost (METHOD=7). Set this keyword to a floating-point value that represents the coefficient of variation cutoff for homogenous areas.

DAMP

Use this keyword to specify the filter damping factor. DAMP is a floating-point number greater than or equal to 0. If you set DAMP to 0, the filter performs like an averaging filter. Use this keyword only when using the Frost filter (METHOD=3).

DIMS 

The “dimensions” keyword is a five-element array of long integers that defines the spatial subset (of a file or array) to use for processing. Nearly every time you specify the keyword FID, you must also specify the spatial subset of the corresponding file (even if the entire file, with no spatial subsetting, is to be processed).

  • DIMS[0]: A pointer to an open ROI; use only in cases where ROIs define the spatial subset. Otherwise, set to -1L.
  • DIMS[1]: The starting sample number. The first x pixel is 0.
  • DIMS[2]: The ending sample number
  • DIMS[3]: The starting line number. The first y pixel is 0.
  • DIMS[4]: The ending line number

To process an entire file (with no spatial subsetting), define DIMS as shown in the following code example. This example assumes you have already opened a file using ENVI_SELECT or ENVI_PICKFILE:

  envi_file_query, fid, dims=dims

FID

The file ID (FID) is a long-integer scalar with a value greater than 0. An invalid FID has a value of -1. The FID is provided as a named variable by any routine used to open or select a file. Often, the FID is returned from the keyword R_FID in the ENVIRasterToFID routine. Files are processed by referring to their FIDs. If you work directly with the file in IDL, the FID is not equivalent to a logical unit number (LUN).

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).

KX 

Use this keyword to specify a square kernel size. KX is an integer greater than or equal to 3.

METHOD 

Use this keyword to specify the type of filter. Choose one of the following:

  • 0: Lee
  • 1: Bit error removal
  • 2: Localized sigma
  • 3: Frost
  • 4: Gamma
  • 5: Kuan
  • 6: Enhanced Lee
  • 7: Enhanced Frost

MULT_MEAN

Use this keyword to specify a variable that contains the multiplicative noise mean. MULT_MEAN is a floating-point number. Use this keyword only when using the Lee filter (METHOD=0) and when NOISE_TYPE=1 or 2.

NLOOK

Use this keyword to specify a variable that contains the number of looks for the data. NLOOK is an integer. Use this keyword only when using the gamma and Kuan filters, METHOD=4 and METHOD=5, respectively.

NOISE_TYPE

Use this keyword to specify the type of noise. Set NOISE_TYPE to one of the following integer values:

  • 0: Additive noise
  • 1: Multiplicative noise
  • 2: Both

OUT_BNAME

Use this keyword to specify a string array of output band names.

OUT_NAME

Use this keyword to specify a string with the output filename for the resulting data. If you set the keyword IN_MEMORY, you do not need to specify OUT_NAME.

POS

Use this keyword to specify an array of band positions, indicating the band numbers on which to perform the operation. This keyword indicates the spectral subset of bands to use in processing. POS is an array of long integers, ranging from 0 to the number of bands minus 1. Specify bands starting with zero (Band 1=0, Band 2=1, etc.) For example, to process only Bands 3 and 4 of a multi-band file, POS=[2, 3].

POS is typically used with individual files. The example code below illustrates the use of POS for a single file with four bands of data:

  pos=[0,1,2,3]
                  
envi_doit, 'envi_stats_doit', dims=dims, fid=fid, pos=pos, $
                  
comp_flag=3, dmin=dmin, dmax=dmax, mean=mean, stdv=stdv, hist=hist

But what if you need to create an output file consisting of data from different bands, each from different files? Library routines such as CF_DOIT and ENVI_LAYER_STACKING_DOIT can accomplish this, but they use the POS keyword differently. Suppose you have four files, test1, test2, test3, and test4, with corresponding FIDs of fid1, fid2, fid3, and fid4, respectively. In the following example, you want Band 3 from test1 in the first position, Band 2 from test2 in the second position, Band 6 from test3 in the third position, and Band 4 from test4 in the fourth position. The code should be as follows:

  fid_array = [fid1,fid2,fid3,fid4]
                  
pos=[2,1,5,3]
                  
envi_doit, 'cf_doit', dims=dims, fid=fid_array
                  
out_name='test_composite_file'

REPLACE

Set this keyword to replace bit errors with the local average. Use this keyword only when METHOD=1.

R_FID

ENVI Classic library routines that result in new images also have an R_FID, or “returned FID.” This is simply a named variable containing the file ID to access the processed data. Specifying this keyword saves you the step of opening the new file from disk.

SIGMA

Use this keyword to specify a sigma value when METHOD=0, or a sigma factor when METHOD=1 or 2.

TOL

Use this keyword to specify the maximum standard deviation tolerance. Use only when METHOD=1.

VMAX

Use this keyword to specify the maximum value for valid data. Use only when METHOD=1.

VMIN

Use this keyword to specify the minimum value for valid data. Use only when METHOD=1.