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ISIS 3 Application Documentation


bit2bit

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Change the bit-type of pixel data

Description
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History


Description

bit2bit allows the user to change the bit-type of a cube to 8, 16, or 32-bit.

Since the pixel type will typically be modified with this procedure, if a non-32 bit output is selected some binning will be done to accomodate the output data's new bit type. To minimize over or underbinning, the user can choose values MINPER and MAXPER or MIN and MAX to clip the original data set. MINPER and MAXPER denote minimum and maximum percentages on the cumulative histogram of the incoming cube data that you wish to be represented in the output cube. MIN and MAX represent the minimum and maximum pixel values you wish to have represented in the output cube. All pixels under MIN or MINPER get set to LRS in the output cube while all pixels over MAX or MAXPER get mapped to HRS.

Why would one wish to clip data off a perfectly good cube? The example below illustrates why:


Below is an incoming image shown in a histogram:



If we were to convert this image to 8-bit directly, 50 % of the bins would be occupied by only 2.5% of the data (DN's in the range 12500-15000) as shown below:




To minimize over or under binning in the output image, the user can chose to only accept data within the range bounded by MINPER and MAXPER on the cumulative histogram. In the example above, if the user set MINPER=0 and MAXPER=97.5, the 8-bit range (including base and multiplier) would include DN's in the range 10,000 to 12,500. A DN above 12500 would be set as the special pixel HRS.

Any data that gets scaled out of range gets converted to the special pixels LRS (if the DN is below the value corresponding to the minimum percentile specified by MINPER) or HRS (if the DN is above the value corresponding to the maximum percentile specified by MAXPER).


Categories


Related Objects and Documents

Applications


Parameter Groups

Files

Name Description
FROM Input file
TO Output cube

Output Bit Type

Name Description
BITTYPE Determines the bit type of the ouput pixel

Clipping Method

Name Description
CLIP Clip by Percentage or Min/Max

Extrema

Name Description
MINPER User-defined minimum percent
MAXPER User-defined maximum percent
MINVAL User-defined minimum value
MAXVAL User-defined maximum value

Stats

Name Description
STATSInclude output cube statistics in summary reporting

Files: FROM

Description

The input cube whose pixel types are to be modified

Type cube
File Mode input
Filter *.cub

Files: TO

Description

The resultant cube containing the modified data

Type filename
File Mode output

Output Bit Type: BITTYPE

Description

Determines the bit type of the ouput pixel: Options are 8BIT, 16BIT, and 32BIT (default).

Type string
Default 32BIT
Option List:
Option Brief Description
8BIT8 bit output pixels The input pixels will be converted to unsigned 8-bit values in the output cube.
16BIT16 bit output pixels The input pixels will be converted to signed 16-bit values in the output cube.
32BIT32 bit output pixels The input pixels will be converted to 32 bit floats in the output cube.

Exclusions

  • MINPER
  • MAXPER

Clipping Method: CLIP

Description

Optionally clip the ends of cube data by percentage on cumulative histogram or by Min/Max pixel values

Type string
Default PERCENT
Option List:
Option Brief Description
PERCENTClip by percentage Clip by percentage on cumulative histogram of pixel values (default)

Exclusions

  • MINVAL
  • MAXVAL
MINMAXClip by Min/Max Clip by Min/Max pixel values

Exclusions

  • MINPER
  • MAXPER

Extrema: MINPER

Description

Choose the minimum percentile to represent from the cumulative data histogram of the pixel values from the incoming cube. For example: The default MINPER value of .5 will discard the lowest .5% of the data values from the incoming cube.

Type double
Default 0.5
Minimum 0.0 (inclusive)

Extrema: MAXPER

Description

Choose the maximum percentile to represent from the cumulative data histogram of the pixel values from the incoming cube. For example: The default MAXPER value of 99.5 will discard the upper .5% of the data values from the incoming cube.

Type double
Default 99.5
Maximum 100.0 (inclusive)

Extrema: MINVAL

Description

Choose the minimum pixel value to be represented by a valid pixel in the output cube

Type double
Default 0.0

Extrema: MAXVAL

Description

Choose the maximum pixel value to be represented by a valid pixel in the output cube

Type double
Default 255.0

Stats: STATS

Description

If enabled, will include output cube statistics in summary reporting. If disabled, bit2bit runs significantly faster.

Type boolean
Default True

History

Philip Martinez2010-06-10 Original version