.. _BandMath: 

BandMath
========





Outputs a monoband image which is the result of a mathematical operation on several multi-band images.

Description
-----------

This application performs a mathematical operation on several multi-band images and outputs the result into a monoband image. The given expression is computed at each pixel position. Evaluation of the mathematical formula is done by the muParser library.

The formula can be written using:

* numerical values ( 2.3, -5, 3.1e4, ...)
* variables containing pixel values (e.g. ``im2b3`` is the pixel value in 2nd image, 3rd band)
* binary operators:

  * ``+`` addition, ``-`` subtraction, ``*`` multiplication, ``/`` division
  * ``^`` raise x to the power of y
  * ``<`` less than, ``>`` greater than, ``<=`` less or equal, ``>=`` greater or equal
  * ``==`` equal, ``!=`` not equal
  * ``||`` logical or, ``&&`` logical and
  * if-then-else operator: ``(condition ? value_true : value_false)``
* functions: ``exp()``, ``log()``, ``sin()``, ``cos()``, ``min()``, ``max()``, ...

The full list of features and operators is available on the muParser website [1].



Parameters
----------

.. contents:: :local:

.. |br| raw:: html

   <br />

.. |em| raw:: html

   &emsp;

**Input image list** :code:`-il image1 image2...` *Mandatory* |br|
Image list of operands to the mathematical expression.

**Output Image** :code:`-out image [dtype]` *Mandatory* |br|
Output image which is the result of the mathematical expressions on input image list operands.

**Expression** :code:`-exp string` *Mandatory* |br|
The muParser mathematical expression to apply on input images.

**Available RAM (MB)** :code:`-ram int` *Default value: 256* |br|
Available memory for processing (in MB).



Examples
--------

From the command-line:

.. code-block:: bash

    otbcli_BandMath -il verySmallFSATSW_r.tif verySmallFSATSW_nir.tif verySmallFSATSW.tif -out apTvUtBandMathOutput.tif -exp "cos( im1b1 ) > cos( im2b1 ) ? im3b1 : im3b2"


From Python:

.. code-block:: python

	import otbApplication

	app = otbApplication.Registry.CreateApplication("BandMath")

	app.SetParameterStringList("il", ['verySmallFSATSW_r.tif', 'verySmallFSATSW_nir.tif', 'verySmallFSATSW.tif'])
	app.SetParameterString("out", "apTvUtBandMathOutput.tif")
	app.SetParameterString("exp", "cos( im1b1 ) > cos( im2b1 ) ? im3b1 : im3b2")

	app.ExecuteAndWriteOutput()





See also
--------

| [1] http://beltoforion.de/article.php?a=muparser