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ISIS Documentation

bit2bit

Change the bit-type of pixel data

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

History

Philip Martinez2010-06-10 Original version
Jacob Cain2022-11-22 Changed TO type to cube. Fixes #4780.

Parameters

Files

The input cube whose pixel types are to be modified
Type cube
File Mode input
Filter *.cub

The resultant cube containing the modified data
Type cube
File Mode output
Filter *.cub

Output Bit Type

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

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

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)

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)

Choose the minimum pixel value to be represented by a valid pixel in the output cube
Type double
Default 0.0

Choose the maximum pixel value to be represented by a valid pixel in the output cube
Type double
Default 255.0

Stats

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