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General Utility


Introduction


The suite of ISIS3 image processing applications perform a wide variety of functions to manipulate the image data. Occasionally, there is a need to apply a unique set of equations to correct or produce an image that none of the existing programs will perform, such as applying a gamma stretch or creating a cube file based on a mathematical equation. In these instances, using the fx program may accomplish the task. The application is still under development so it may take multiple steps, especially if the AND and/or OR logical operators are needed. The modulus (%), AND, and OR operators are not implemented yet.

String Parameters


The command line parsing has been improved to handle escape sequences and support arrays better. The equation parser is case insensitive, ignores whitespace, and converts all braces to parentheses.

The command line syntax changes are as follows (with TCSH/BASH examples):
Parameter values, when quoted, no longer need the quotes escaped:

TCSH/BASH

Before:

crop from=\"some file.cub\" to=\"output file.cub\"

Now:

crop from="some file.cub" to="output file.cub"

Please note that dollar signs ($) still need to be backslashed for batchlist variables.
Array values, for programs such as spiceinit, will be much the same.

TCSH

Before:

spiceinit from=input.cub ck='(file1.bc,file2.bc)'

Now:

spiceinit from=input.cub ck='(file1.bc,file2.bc)'

BASH

Before:

spiceinit from=input.cub ck='(file1.bc,file2.bc)'

Now:

spiceinit from=input.cub ck='(file1.bc,file2.bc)'

However, an escape has been added to differentiate a first parenthesis from the beginning of an array sequence.

TCSH

Before:

fx equation='"(1+2)/2"'

Now:

fx equation='\(1+2)/2'

BASH

Before:

fx equation='"(1+2)/2"'

Now:

fx equation=\(1+2)/2

The equation string entered within a GUI interface may not work if the entire string is copied, and executed at the command line. If the first character in the equation is a "(" then it must be prefixed by a "\" if executing at the command line, but the remaining parentheses do not need to be prefixed with a backslash.

For example:

Works inside fx GUI:

fx f1=BIFQF23N004_D218_T069S02_V02_I3.cub to=tt.cub equation=(f1*(f1>.004))

Fails on the command line:

fx f1=BIFQF23N004_D218_T069S02_V02_I3.cub to=tt.cub equation=(f1*(f1>.004))
fx f1=BIFQF23N004_D218_T069S02_V02_I3.cub to=tt.cub equation="(f1*(f1>.004))"

Works on the command line:

fx f1=BIFQF23N004_D218_T069S02_V02_I3.cub to=tt.cub equation="\(f1*(f1>.004))"

For additional information see fx command page
Note: some instructions may be outdated.

Input Data


The input data can be a single band or multiple band cube file. Up to five files can be entered for parameters f1 to f5, or an arbitrary number of files can be included in a file list and entered for the fromlist parameter. The other option is to only create an output file based on a user defined equation. If the band number is not specified for the multiple band cube files, then the equation is applied to all the bands in the file.

Example

f1=file1.cub f2=file2.cub f3=file4.cub f5=file5.cub  

or

ls *lev1.cub > files.lis
from=files.lis

Requirements and result of operators


The following operators return a "0" or "1" DN value when they are used in the equations:

  • <
  • >
  • <=
  • >=
  • ==
  • !=

The following operators require that the images be ran through spiceinit first, so that the necessary information can be extracted based on the camera model information stored in the image labels:

  • pha, phal, phac
  • ina, inal, inac
  • ema, emal, emac
  • lat
  • lon
  • radius
  • resolution

The following are used to convert between degrees and radians:

  • rads
  • degs

Note: All trigonometric functions expect angles in radians, not degrees. However, all camera functions return angles in degrees and therefore should be converted to radians

The following operators use the input image statistics to apply the equations:

  • linemin
  • linemax
  • cubemin
  • cubemax
  • cubeavg
  • cubestd

The following are used to compare two input values (user entered and/or from input files):

  • min
  • max

The following shifts the pixels left or right:

  • <<
  • >>

For example:

  f1 << 10
  S1 L1 = S10 L1
  S2 L1 = S11 L1
  ...
  SN-10 L1 = Null
  SN-9 L1 = Null

Trigonometric functions:

  • sin, cos, tan
  • acos, atan, atan2
  • sinh, cosh, tanh
  • csc, sec, cot

Operators:

  • + - * / ^
  • abs, sqrt, neg or --
  • log10,log or ln

Create only an output file


The example below uses the line number (representing degrees) as input into the cosine function to create a (100 lines by 100 samples) output file. Input values representing degrees must be used with caution because different results are produced if the input value is not converted to radians first or the output not converted back to degrees:

Example 1:

fx to=test_cosrad.cub equation="cos(rads(line))" mode=outputonly lines=100 samples=100

Image created with the cosine function of the line numbers after converting to radians:
fx cosine

Example 2:

fx to=test_cos.cub equation=cos(line) mode=outputonly lines=100 samples=100

Image created with the cosine function of line numbers without converting to radians first:
Fx_cosine_of_LineNum.png

Apply equations to existing cube files


Create an output cube that isolates all pixel values greater than .00015 for band 1:

fx f1=I10645014RDR.lev1crop.cub+1 to=mask1.cub equ="f1>.00015"

Fx_mask_singleband_example.png
Image created with the equation="f1>.00015"
Note: The DN values are now "0" and "1"

Create an output cube that isolates all pixel values greater than .00015 for band1 and retains the input DN values:

fx f1=I10645014RDR.lev1crop.cub+1 to=mask2.cub equ="f1*(f1>.00015)"

Fx_mask_singleband_example2.png
Image created with the equation="f1(f1>.00015)"*
Note: The DN values are now "0" in the areas where the input values was less than 0.00015

Create an output cube that isolates all pixel values greater than .00015 for all bands:

fx f1=I10645014RDR.lev1crop.cub to=mask3.cub equ="f1*(f1>.00015)"

Fx_mask_allbands_example.png
Image created with the equation="f1(f1>.00015)"*
Note: The DN values are now "0" in the areas where the input values was less than 0.00015 in all ten bands, and appears as green in the color file.

Below is the image label of the multiple band cube used as input in the example above. Notice there is no instrument information, so this particular file cannot be run through spiceinit. In addition, none of the functions requiring a camera model can be used on the 10 band cube file.

 Object = IsisCube
  Object = Core
    StartByte   = 65537
    Format      = Tile
    TileSamples = 320
    TileLines   = 500 

    Group = Dimensions
      Samples = 320
      Lines   = 2500
      Bands   = 10   *** NOTE: multiple bands ***
    End_Group 

    Group = Pixels
      Type       = Real
      ByteOrder  = Lsb
      Base       = 0.0
      Multiplier = 1.0
    End_Group
  End_Object 

  Group = BandBin
    Center       = (6.78, 6.78, 7.93, 8.56, 9.35, 10.21, 11.04, 11.79, 12.57,
                    14.88)
    Width        = (1.01, 1.01, 1.09, 1.16, 1.20, 1.10, 1.19, 1.07, 0.81,
                    0.87)
    OriginalBand = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
  End_Group 

  Group = AlphaCube
    AlphaSamples        = 320
    AlphaLines          = 10768
    AlphaStartingSample = 0.5
    AlphaStartingLine   = 2859.5
    AlphaEndingSample   = 320.5
    AlphaEndingLine     = 5359.5
    BetaSamples         = 320
    BetaLines           = 2500
  End_Group
 End_Object  

 Object = Label
  Bytes = 65536
 End_Object 

Apply a gamma stretch to an input file:

fx f1=B10_013516_1520_XN_28S285W_eo.cub to=B10_013516_1520_XN_28S285W_eo_gst.cub equation="{[cubemax(f1)-abs(cubemin(f1))]*{[f1-abs(cubemin(f1))]/[cubemax(f1)-abs(cubemin(f1))]}^(1.0/1.8)}

Fx_CTX_pre_post_gamma_stretch_example.png
Image created with the equation="{[cubemax(f1)-abs(cubemin(f1))]{[f1-abs(cubemin(f1))]/[cubemax(f1)-abs(cubemin(f1))]}1.0/1.8}"*

The CTX image has instrument information that can be used with some of the functions that require camera model information. The following is a partial list of the label contents to show as example:

 Object = IsisCube
  Object = Core
    StartByte   = 65537
    Format      = Tile
    TileSamples = 500
    TileLines   = 512 <br>
    Group = Dimensions
      Samples = 5000
      Lines   = 52224
      Bands   = 1
    End_Group

    Group = Pixels
      Type       = Real
      ByteOrder  = Lsb
      Base       = 0.0
      Multiplier = 1.0
    End_Group
  End_Object

  Group = Instrument
    SpacecraftName        = Mars_Reconnaissance_Orbiter
    InstrumentId          = CTX
    TargetName            = Mars
    MissionPhaseName      = PSP
    StartTime             = 2008-06-09T20:17:54.712
    SpacecraftClockCount  = 0897509894:216
    OffsetModeId          = 196/190/181
    LineExposureDuration  = 1.877 <MSEC>
    FocalPlaneTemperature = 292.4 <K>
    SampleBitModeId       = SQROOT
    SpatialSumming        = 1
    SampleFirstPixel      = 0
  End_Group

  Group = Archive
    DataSetId           = MRO-M-CTX-2-EDR-L0-V1.0
    ProductId           = '''''P20_008770_1328_XI_47S308W'''''
    ProducerId          = MRO_CTX_TEAM
    ProductCreationTime = 2009-01-20T23:37:21
    OrbitNumber         = 8770
  End_Group

  Group = BandBin
    FilterName = BroadBand
    Center     = 0.65 <micrometers>
    Width      = 0.15 <micrometers>
  End_Group

  Group = Kernels
    NaifFrameCode             = -74021
    LeapSecond                = $base/kernels/lsk/naif0009.tls
    TargetAttitudeShape       = $base/kernels/pck/pck00009.tpc
    TargetPosition            = (Table, $base/kernels/spk/de405.bsp)
    InstrumentPointing        = (Table,
                                 $mro/kernels/ck/mro_sc_psp_080603_080609.bc,
                                 $mro/kernels/fk/mro_v14.tf)
    Instrument                = Null
    SpacecraftClock           = $mro/kernels/sclk/MRO_SCLKSCET.00046.65536.tsc
    InstrumentPosition        = (Table, $mro/kernels/spk/mro_psp7.bsp)
    InstrumentAddendum        = $mro/kernels/iak/mroctxAddendum004.ti
    ShapeModel                = $base/dems/molaMarsPlanetaryRadius0005.cub
    InstrumentPositionQuality = Reconstructed
    InstrumentPointingQuality = Reconstructed
    CameraVersion             = 1
  End_Group

  Group = Radiometry
    FlatFile = /usgs/cpkgs/isis3/data/mro/calibration/ctxFlat_0002.cub
    iof      = 2.10004797011897e-04
  End_Group
 End_Object

Create an output cube that divides the input pixel by the cosine of the incidence angle to perform a simple photometric correction:

fx f1=P20_008770_1328_XI_47S308W_eo.cub to=fx_cosi.cub equation="f1/cos(rads(ina(f1)))

Fx_cosine_inc_angle.png
Image created with the equation="f1/cos(rads(ina(f1)))"
Note: The brightness of the image on the right has been normalized throughout the image.

Other command line entry examples:


Output data values in logarithmic form using three different options:

Option 1:

fx f1=BIF_I3.cub to=BIB_test.cub+Lsb+BandSequential+Attached+UnsignedByte+-20.05:5.35<br>
    equation="max(-20.0,min{10.0*log10[max(0.01,f1)],5.0})"

Option 2:

fx f1=BIF_I3.cub to=BIB_test.cub+Lsb+BandSequential+Attached+UnsignedByte+-20.05:5.35
  equation="max(min(10.0*log10(max(f1,0.01)),5.0),--20.0)"

Option 3:

fx f1=BIF_I3.cub to=BIB_test.cub+Lsb+BandSequential+Attached+UnsignedByte+-20.05:5.35
  equation="max(neg (20.0),min{10.0*log10[max(0.01,f1)],5.0})"'

Other examples of applying algebraic equations:

fx f1=test1.cub f2=test2.cub equ="\(f1-f2)/(f1+f2)" to=result.cub
fx f1=test1.cub f2=test2.cub equ="f1-(f2*0.77)" to=result.cub
fx f1=test.cub to=new_test.cub equation="f1/cos(rads(pha(f1)))"
fx f1=test1.cub f2=test2.cub f3=test3.cub f4=test4.cub equation="\(sqrt(f2^2+f3^2+f4^2))/f1" to=test.cub

Fx_mask_singleband_example2.png View (79.2 KB) Kristin Berry, 2016-05-31 04:03 PM

Fx_mask_singleband_example.png View (71.9 KB) Kristin Berry, 2016-05-31 04:03 PM

Fx_cosine_of_LineNum_radian.png View (10.7 KB) Kristin Berry, 2016-05-31 04:03 PM

Fx_cosine_of_LineNum.png View (10.7 KB) Kristin Berry, 2016-05-31 04:03 PM

Fx_mask_allbands_example.png View (99.3 KB) Kristin Berry, 2016-05-31 04:03 PM

Fx_cosine_inc_angle.png View (273 KB) Kristin Berry, 2016-05-31 04:03 PM

Fx_CTX_pre_post_gamma_stretch_example.png View (290 KB) Kristin Berry, 2016-05-31 04:03 PM