.. _SampleExtraction: 

SampleExtraction
================





Extracts samples values from an image.

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

The application extracts samples values from animage using positions contained in a vector data file. 



Parameters
----------

.. contents:: :local:

.. |br| raw:: html

   <br />

.. |em| raw:: html

   &emsp;

**InputImage** :code:`-in image` *Mandatory* |br|
Support image

**Input sampling positions** :code:`-vec vectorfile` *Mandatory* |br|
Vector data file containing samplingpositions. (OGR format)

**Output samples** :code:`-out filename [dtype]` |br|
Output vector data file storing samplevalues (OGR format). If not given, the input vector data file is updated

**Output field names** :code:`-outfield [prefix|list]` *Default value: prefix* |br|
Choice between naming method for output fields

* **Use a prefix and an incremental counter** |br| Use a prefix and an incremental counter

* **Use the given name list** |br| Use the given name list



Use a prefix and an incremental counter options
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

**Output field prefix** :code:`-outfield.prefix.name string` *Default value: value_* |br|
Prefix used to form the field names thatwill contain the extracted values.

Use the given name list options
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

**Output field names** :code:`-outfield.list.names string1 string2...` *Mandatory* |br|
Full list of output field names.



------------

**Field Name** :code:`-field string` |br|
Name of the field carrying the class name in the input vectors.

**Layer Index** :code:`-layer int` *Default value: 0* |br|
Layer index to read in the input vector file.

**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_SampleExtraction -in support_image.tif -vec sample_positions.sqlite -outfield prefix -outfield.prefix.name band_ -field label -out sample_values.sqlite


From Python:

.. code-block:: python

	import otbApplication

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

	app.SetParameterString("in", "support_image.tif")
	app.SetParameterString("vec", "sample_positions.sqlite")
	app.SetParameterString("outfield","prefix")
	app.SetParameterString("outfield.prefix.name", "band_")
	app.SetParameterString("field", "label")
	app.SetParameterString("out", "sample_values.sqlite")

	app.ExecuteAndWriteOutput()