Parent Topic: STR

PARAMETERS

STR is controlled by the following global parameters:

Name     Prompt                                  Count     Type
FILE     Database File Name                      1-64      Char
DBIC     Database Input Channel List             0-1       Int
DBLUT    Database Lookup Table                   0-1       Int
DBSN     Database Segment Name                   0-8       Cha
DBSD     Database Segment Descriptor             0-64      Char
EXPO     Exponent for Contrast Stretch           1         Real
ISTR     Input Stretch Range (Min,Max)           0-2       Int
OSTR     Output Stretch Range (Min,Max)          0-2       Int
LCTR     Low End Control: MIN/MAX/OFF            3         Char
HCTR     High End Control: MIN/MAX/OFF           3         Char
TRIM     Tail Trimming % (Left, Right)           0-2       Real
MASK     Area Mask (Window or Bitmap)            0-4       Int

The following parameter receives output:

DBLUT    Database Lookup Table                   0-1       Int

FILE

Specifies the name of the PCIDSK file to receive the lookup table segment.

 EASI>FILE="filespec"

DBIC

Specifies the database input channel from which `actual' min and max grey level for stretching are determined.

 EASI>DBIC=i

DBIC and ISTR cannot both be specified.
One of DBIC, ISTR must be specified.
DBIC should be 8-bit type channels, for 16-bit and
32-bit channels values will be truncated to 8-bit.

DBSN

Specifies a 1 to 8-character identifier that will be assigned to the output lookup table segment. This string is displayed by ASL, and may be changed with MAS.

 EASI>DBSN="seg name"

DBSN is only required if a new segment is created.

DBSD

Optionally specifies a 1 to 64-character descriptor that will be associated with the output segment. This string is displayed by ASL if LTYP = "MEDIum" or "FULL", and may be changed with MAS.

EASI>DBSD="string describing contents or origin of data"

DBSD may only be used if a new segment is created.

ISTR

Specifies the range of input grey levels.

 EASI>ISTR=i,j

DBIC and ISTR cannot both be specified.
One of DBIC, ISTR must be specified.
Default is 0,255.
i must be in range [0,254].
j must be in range [1,255].
j must be greater than or equal to i.
Only grey values in this range will be stretched; the rest are treated in accordance with the parameters OSTR, LCTR and HCTR.

OSTR

Specifies the range of output grey levels.

 EASI>OSTR=i,j

Default is 0,255.

TRIM

Optionally specifies the amount of tail trimming of the image histogram sample.

 EASI>TRIM=n1,n2

These are real values in units of % (between 0 and 100).
n1 is for left (low) tail, n2 is for right (high).
Default is no tail trimming.
Trimming is performed only if DBIC is set.

MASK

Specifies the area in the input channel which should be stretched. This can be one of the following:

 EASI>MASK=xoff,yoff,xsize,ysize        | process window
 EASI>MASK=b                            | process only under bitmap
                                        | stored in segment b
 EASI>MASK=                             | process entire channel

Note: MASK is only pertinent if DBIC is specified.

EXPO

  Valid Values:   0.0 <= x <= 100.0
  Default:        0.5

Specifies a positive real number corresponding to the exponent in the contrast stretching formula:

   newval = A*(oldval - ISTR(1))**EXPO + OSTR(1)

where newval and oldval are grey levels, A is the scaling factor, and ISTR(1) and OSTR(1) are the minimum input and output grey levels. For instance, if EXPO is set to 1, the stretch is linear.

EXPO defaults to 0.5 (this eliminates the typical skewing of histograms).

 EASI>EXPO=n
 EASI>EXPO=             | defaults to 0.5

LCTR

  Valid Values:   OFF,MIN,MAX
  Default:        MIN

Specifies the mapping of pixels that fall short of the input range in ISTR(1).

 EASI>LCTR="OFF"        | low-end values unchanged
 EASI>LCTR="MIN"        | low-end values set to bottom of
                        | output range (OSTR(1))
 EASI>LCTR="MAX"        | low-end values set to top of
                        | output range (OSTR(2))

HCTR

  Valid Values:   OFF,MIN,MAX
  Default:        MAX

Specifies the mapping of pixels that are higher than the input range in ISTR(2).

 EASI>HCTR="OFF"        | high-end values unchanged
 EASI>HCTR="MIN"        | high-end values set to bottom of
                        | output range (OSTR(1))
 EASI>HCTR="MAX"        | high-end values set to top of
                        | output range (OSTR(2))

DBLUT

Specifies the lookup table segment on the database to receive the function.

 EASI>DBLUT=i

DBLUT must contain one or no elements.
If DBLUT is explicitly specified, that lookup table segment must be of type 170 and will be overwritten.
If DBLUT is defaulted, then a new lookup table segment is created.

Upon completion, DBLUT will return the segment number of the segment used to save the created lookup table function.

Parent Topic: STR
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