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Harris Geospatial / Docs Center / ENVI API / ENVI Classic Data Control / ENVI_DEFAULT_STRETCH_CREATE

ENVI_DEFAULT_STRETCH_CREATE

ENVI_DEFAULT_STRETCH_CREATE

This routine is obsolete and has been replaced with the following routines:
ENVIEqualizationStretchRaster
ENVIGaussianStretchRaster
ENVILinearPercentStretchRaster
ENVILinearRangeStretchRaster
ENVILogStretchRaster
ENVIOptimizedLinearStretchRaster
ENVIRootStretchRaster

This function returns an ENVI Classic default stretch structure, which is used to set the default stretch when displaying data from a file. Create the default stretch structure using ENVI_DEFAULT_STRETCH_CREATE and set the DEF_STRETCH keyword in the ENVI_SETUP_HEAD or ENVI_ENTER_DATA routines. Use this routine instead of directly accessing the default stretch structure.

Syntax


Result = ENVI_DEFAULT_STRETCH_CREATE([, /EQUALIZE] [, /GAUSSIAN] [, /LINEAR] [, /NONE] [, /PCT_LINEAR] [, /SQUARE_ROOT] [, VAL1=value] [, VAL2=value])

Keywords


EQUALIZE (optional)

Set this keyword to create an equalization default stretch structure. The keywords VAL1 and VAL2 are not used with this stretch.

GAUSSIAN (optional)

Set this keyword to create a Gaussian default stretch structure. Use the keyword VAL1 to specify the number of Gaussian standard deviations for the stretch. The default for VAL1 is 2. The keyword VAL2 is not used with this stretch.

LINEAR (optional)

Set this keyword to create a linear range default stretch structure. Use the keyword VAL1 to specify the minimum and VAL2 to specify the maximum values for the linear stretch range. The default values for VAL1 and VAL2 are 0 and 255, respectively.

NONE (optional)

Set this keyword to create a default stretch structure with no stretch defined. The keywords VAL1 and VAL2 are not used with this stretch.

PCT_LINEAR (optional)

Set this keyword to create a percent linear default stretch structure. Use the keyword VAL1 to specify the percentage for the stretch. The default is VAL1=0, specifying a 0% stretch.

SQUARE_ROOT (optional)

Set this keyword to create a square root default stretch structure. The keywords VAL1 and VAL2 are not used with this stretch.

VAL1 (optional)

Set this keyword according to the stretch keyword you set.

  • GAUSSIAN: VAL1 is a floating-point value specifying the Gaussian standard deviation for the stretch
  • LINEAR: VAL1 is a floating-point value specifying the minimum value for the stretch range
  • PCT_LINEAR: VAL1 is a long integer, 0 through 100, specifying the percent of the stretch

Do not use VAL1 when you set the keywords EQUALIZE, NONE, or SQUARE_ROOT.

VAL2 (optional)

Use this keyword only when you set the LINEAR keyword. Set VAL2 to a floating-point value, specifying the maximum value for the stretch range. Do not use VAL2 for any other types of stretches.



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