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ENVI_GET_SLICE

ENVI_GET_SLICE

This routine is obsolete and has been replaced with ENVIRasterIterator.

This function returns the requested spectral slice of data in BIP or BIL storage order. The dimensions of a BIL slice are always [num_samples, num_bands]. A BIP slice is the transpose of the BIL slice, so dimensions are [num_bands, num_samples].

Syntax


Result = ENVI_GET_SLICE([/BIL] [, /BIP], FID=file ID, LINE=integer, POS=array, XE=value, XS=value)

Keywords


BIL (optional)

Set this keyword to return the data in BIL format.

BIP (optional)

Set this keyword to return the data in BIP format.

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).

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'

LINE

Use this keyword to specify the line number to extract the slice from. LINE is a zero-based number.

XE

Use this keyword to specify the x ending value. XE is a zero-based number.

XS

Use this keyword to specify the x starting value. XS is a zero-based number.



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