<< Click to Display Table of Contents >> Navigation:  Help Content > General Tools > Data Export > General Tools - Data Export - Generate Color Composite

Purpose

 

An RGB image can be generated from coregistered or geocoded images. Predefined RGB combination schemes are available.

 

Technical Note

Specific scale and exponent values can be applied to modify the Red, Green and Blue component in the RGB composite. The suggested procedure it is to first run the processing using the default parameters; the "leave temporary file" flag must be set in order to leave the three separated colour channels (temporary files) after the process is completed. In a possible successive processing iteration, increase one or more "Scale" values in order to give more weight to a specific color channel. The "Exponent" shall be changed in case the image contrast has to be modified. After the first process iteration, the flag "Only RGB generation" must be set in order to re-use previously generated temporary files.

 

The flag "Use Entered Values Only" can be set in order to scale the original pixel values only on the basis of the figures provided in the "Scale" and "Exponent" boxes; in such case the formula applied is:

output value = scale . input valueexponent

 

If the option "Use Entered Values Only" is not used, the original data will be scaled by means of the following formula:

output value = [(254 .  0.33333 . Scale) / Mean( subsetvalueexponent)] . (input value)exponent

 

In case negative values were present, the flag "Negative" must be set for the relevant layer when the option "Use Entered Values Only" is selected.

 

The histogram scaling values - relevant respectively to the Red, Green and Blue channels - are written in the "SARscape>View Files>Process.log" file.

 

In case the output product must have the same size (i.e. same number of pixels) of a reference image, this image has to be entered as "Input reference file".

 

All images geocoded to the GEO-GLOBAL reference system (LAT/LONG co-ordinates) can be automatically displayed into the Google Earth environment by double clicking on the output kml file.

 

Input Files

 

Input files list

Input files (_pwr, _geo, _fil) to make the RGB image. These files are mandatory.

 

Optional Files

 

Input reference file

Input file to be used as reference for the output file dimension. The output color composite will have the same size of the input reference file. This file is optional.

 

Parameters - Principal Parameters

 

Operation type

One of the following operations can be performed on the input files:

 

•standard RGB

The three input files are assigned respectively to the Red, Green and Blue channel in a color combination.

 

•MTC

The following color combination is obtained: Red = input (Reference); Green = input 2 (Secondary); Blue = input 3 (Coherence).

 

•MUCD

The following color combination is obtained: Red = input 1 [(1-Coherence)]; Green = input 2 [(1-Coherence)]; Blue = input 3 [(1-Coherence)].

 

•CoPol CrossPol composite1

The following color combination is obtained: Red = (input 1 - input 2) / (input 1 + input 2); Green = input 2; Blue = input 1.

 

•CoPol CrossPol composite2

The following color combination is obtained: Red = input 1; Green = input 2; Blue = arctg (input 2/input 1).
 
Note: For CoPol CrossPol composites, it is suggested to use as input 1 the CoPol image and as Input 2 the CrossPol one.

 

•unsigned coherence combination (ILU)

The coherence (1st input) and two Intensity images (2nd and 3rd input) must be provided as input. In the output RGB image (unsigned format) the Red channel is the coherence; the Green channel is the mean Intensity; the Blue channel is the Intensity difference (2nd - 3rd).

 

R = coherence between image1 and image2

G = absolute average between image1 and image2

B = absolute difference between image1 and image2 (the Blue channel stretch is improved)

 

•signed coherence combination

As above, but in signed format.

 

R = coherence between image1 and image2

G = absolute average between image1 and image2

B = difference between image1 and image2 (the Blue channel shows the difference sign too)  

 

RED/GREEN/BLUE Scale

Changing this value affects the brightness of each output color layer: the higher these values the brighter the image.

 

RED/GREEN/BLUE Exponent

An exponential scaling factor is applied. Changing this value affects the contrast of each output color layer: values higher than 1 enable to optimize the stretch of high pixel values (bright areas); values lower than 1 enable to optimize the stretch of low pixel values (dark areas).

 

RED/GREEN/BLUE Use Entered Values Only

The input values are scaled only on the basis of the specified "Scale" and "Exponent".

 

RED/GREEN/BLUE Negative

This flag must be checked in case the input files contain negative pixel values.

 

Only RGB Generation

By setting this flag the only the RGB file is generated.

 

White dummy

By setting this flag the RGB image background, as well as dummy pixels within the imaged area, are shown in white (default is black).

 

Common scaling

By setting this flag the scaling factor is not calculated independently for each RGB layer; the same scaling factor, which is calculated for the first layer (Red channel), is applied to the other 2 layers (Green and Blue channels).

 

Mean in common scaling

By setting this flag the same scaling factor, which is calculated from the mean of the three layers, is applied to each of the three layers.

 

Parameters - Global

 

It brings to the general section of the Preferences parameters. Any modified value will be used and stored for further processing sessions.

 

Parameters - Other Parameters

 

It brings to the general section of the Preferences parameters. Any modified value will be used and stored for further processing sessions.

 

Output Files

 

Output file

Enter the name of the output file (Tiff format). This file is mandatory.

 

.tif        

Tiff image and corresponding header file (.sml).

 

.kml

ASCII file containing the information to visualize the Tiff image in Google Earth. It is generated only for images geocoded using the GEO-GLOBAL reference system.

 

Details specific to the Units of Measure and Nomenclature of the output products can be found in the Data Format section.

 

General Functions

 

Exec

The processing step is executed.

 

Store Batch        

The processing step is stored in the batch list. The Batch Browser button allows to load the batch processing list.

 

Close        

The window will be closed.

 

Help

Specific help document section.

 

 

Specific Function(s)

 

None.

 

See Also

 

Task, SARscapeBatch object, SARscapeBatch script example

 

References

 

None.