ISIS Application Documentation
Change the bit-type of pixel data
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
Applications
History
Philip Martinez | 2010-06-10 |
Original version
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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
|
STATS | Include 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 |
8BIT | 8 bit output pixels |
The input pixels will be converted to unsigned 8-bit values in the
output cube.
|
16BIT | 16 bit output pixels |
The input pixels will be converted to signed 16-bit values in the
output cube.
|
32BIT | 32 bit output pixels |
The input pixels will be converted to 32 bit floats in the output
cube.
Exclusions
|
|
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 |
PERCENT | Clip by percentage |
Clip by percentage on cumulative histogram of pixel values
(default)
Exclusions
|
MINMAX | Clip by Min/Max |
Clip by Min/Max pixel values
Exclusions
|
|
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
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 |