## ISIS 2

ISIS Application Documentation

# hiequal

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Tonematches a set of HiRISE cubes prior to mosaicking

## Description

This program can be used to tonematch or equalize the brightness and contrast of the input HiRISE cubes prior to mosaicking. The set of N cubes inputed must be all Red, all Blue-Green, or all Infared, where N is an integer 2-10 for RED sets and exactly 2 both for IR and BG sets. The order the cube names are provided in does not matter, but the cubes must all follow a linear sequence without skipping cubes all the same (i.e., the user cannot run this application on cubes RED1-RED3 and RED5 without also providing the program RED4). Statistics are gathered by line, taking into account the bin number of the cube (automatically derived from the number of samples in the line). The statistics are used in an IntersectionStatistics object's least squares solution to determine multiplicative and additive corrections to each image. The user has the option to stop the processing after the statistics and corrective factors have been computed for examination. Alternatively, the processing can continue and the corrective factors will be applied to each image (by making sure the APPLY checkbox is ticked). The actual equation to be used for each cube is:

```            newdn(s,l)   =   (olddn(s,l) - avg()) * MULT() + avg() + BASE()
```
where
```            s = sample index
l = line index
```

The BASE and MULT values are computed independently for each image, therefore we have two least squares computations with M unknowns, where M is the number of cubes to be equalized. The intersections, O, between all the cubes are computed and O < M should hold in all cases. In order for the least squares equation to be solved, there must be at least as many knowns as unknowns. Therefore, you must hold one or more cubes to alleviate this problem. Holding a cube forces MULT and BASE to 1.0 and 0.0 respectively.

If the APPLY option is selected, the equalized cubes will be named the same as the input cubes with the addition of a '.equ' prior to the '.cub' extension.

## Parameter Groups

### Files

Name Description
FROMLIST List of cubes to equalize
HOLDLIST List of filenames to hold
TOLIST The list of the equalized cubes to be created
OUTSTATS Text file containing thorough equalization related statistics
INSTATS Input text file containing thorough equalization-related statistics, used for applying correction

### ProcessingOptions

Name Description
PROCESS Calculate statistics, apply correction, or do both

### Files: FROMLIST

#### Description

A list of HiRISE cubes to equalize. The types (i.e., RED, BG, IR) must match in order to do the equalization.

 Type filename input

### Files: HOLDLIST

#### Description

List of cubes that are to be held in the equalization. An additive and a multiplicative factor of 0 and 1 will be applied to all cubes that were held. All cubes listed in this file must also be contained in FROMLIST.

 Type filename input None *.txt *.lis *.lst

### Files: TOLIST

#### Description

This list of output files should contain a file to correspond to each input file. The output files will be written to the exact location with the exact name specified unless it happens to be identical to that of its corresponding input file, in which case an error will be thrown. If this file is not specified, but the APPLY option is still selected, the output cubes will be placed in the directory of its input file, and named the same with the exception of ".equ" extension (e.g. "foobar.cub" becomes foobar.equ.cub").

 Type filename input Automatic *.txt *.lis *.lst

### Files: OUTSTATS

#### Description

This file will contain the statistics of all of the intersecting areas along with the computed equalizing factors (BASE and MULT). Specifying this output file is optional.

 Type filename output None *.txt *.pvl *.lis *.lst

### Files: INSTATS

#### Description

This file must contain the statistics of all of the overlapping areas in every band along with the computed equalizing factors (OFFSET and GAIN) for every image in the FROMLIST.

 Type filename input *.txt *.pvl *.lis *.lst

### ProcessingOptions: PROCESS

#### Description

This option allows the user to decide whether they want to do the equalization calculations and then go on to apply correction afterwards, apply correction to the images off of previously gathered statistics, or do the calculations but not apply correction. If the APPLY option is not selected, you must specify an OUTSTATS file. If it is selected you can still optionally specify an OUTSTATS file and the GAIN/OFFSET values will be applied to each input cube. The names and locations of the output cubes are specified by the TOLIST file.

Type string
Default BOTH
Option List:
Option Brief Description
BOTH Calculate statistics and apply correction This option will calculate statistics on the images, then apply correction off of those results.

#### Exclusions

• INSTATS
CALCULATE Calculate statistics only This option will calculate statistics on the images and print them to an output PVL file, but not correct them.

• TOLIST
• INSTATS

#### Inclusions

• OUTSTATS
APPLY Apply correction only This option will use previously generated statistics to apply correction to the images.

• HOLDLIST
• OUTSTATS
• MINCOUNT
• WEIGHT
• PERCENT

• INSTATS

## Examples

### Example 1

RED Images Equalized

#### Description

This example shows the use of the hiequal application with default settings (i.e., no TO file with APPLY set true). For demonstrative purposes, the first image (RED0) has had its pixel values multiplied by .8 with the "fx" application, and the two images have been mosaicked together with "hiccdstitch".

#### Command Line

hiequal fromlist= ../RedList.lst holdlist= ../RedHoldList.lst
Specify a list of 2 adjacent RED images to equalize along with a holding list of one of the images (RED1) that enables the necessary calculations to be performed. All other options are at default values.

#### Input Image

 Mosaic of unequalized adjacent images. Mosaic of the input images for hiequal Parameter Name: FROMLIST This is a small section of the two input images for this example mosaicked together, showing part of the intersection line prior to tonematching.

#### Output Image

 Output image of mosaic showing results of the hiequal application. Mosaic of the output images for hiequal The same section of the equalized output images mosaicked together after the tonematching has been applied.

## History

 Travis Addair 2009-05-07 Original version Travis Addair 2009-06-08 Fixed test data for compatibility across all systems and improved documentation for clarity Travis Addair 2009-08-06 Changed parameter TO to OUTSTATS and added parameter TOLIST allowing the user to specify the location of output files. Output files are now placed into the directory of the input cube when TOLIST is on the default setting. Statistic gathering results are now placed in the print file. Travis Addair 2011-06-29 Added new INSTATS option in addition to making the program more similar in functionality to "equalizer" all around.