.. _trasterband:

Raster band
___________


Number of bands
+++++++++++++++

.. code-block:: python

    from girs.rast.raster import RasterReader
    from girs.rast.proc import composite
    rasters = [
        'D:/tmp/girs/chirps_basin/chirps-v2.0.2016.01.10.tif',
        'D:/tmp/girs/chirps_basin/chirps-v2.0.2016.01.11.tif']
    r0 = RasterReader(rasters[0])
    r1 = composite(*rasters)
    print r0.get_band_count()
    print r1.get_band_count()

Output::

	1
	2

Band data type
^^^^^^^^^^^^^^

`get_band_data_type()` works in the same way as `get_nodata()`

.. code-block:: python

    from girs.rast.raster import RasterReader
    from girs.rast.proc import composite
    rasters = [
        'D:/tmp/girs/chirps_basin/chirps-v2.0.2016.01.10.tif',
        'D:/tmp/girs/chirps_basin/chirps-v2.0.2016.01.11.tif']
    r0 = RasterReader(rasters[0])
    r1 = composite(*rasters)
    print r0.get_band_data_type()
    print r0.get_band_data_type(1)
    print r0.get_band_data_type([1])
    print r1.get_band_data_type()
    print r1.get_band_data_type(1)
    print r1.get_band_data_type([1])
    print r1.get_band_data_type(2)
    print r1.get_band_data_type([2])
    print r1.get_band_data_type([1, 2])
    print r1.get_band_data_type([2, 1])
	
Output::

	6
	6
	[6]
	6
	6
	[6]
	6
	[6]
	[6, 6]
	[6, 6]

Get band
^^^^^^^^

`get_band()` returns a gdal band. If the dataset goes out of scope, the system will crash. 
It is recommendable to not use `get_band()`. Instead, retrieve from the band what you want 
directly using `girs`.

The following will crash the system, because `dataset` goes out of scope after 
returning the function `my_wrong_get_band()`:

.. code-block:: python

    def my_wrong_get_band():
        from osgeo import gdal
        dataset = gdal.Open('D:/tmp/girs/chirps_basin/chirps-v2.0.2016.01.10.tif', gdal.GA_ReadOnly)
        return dataset.GetRasterBand(1)
    
	band = my_wrong_get_band()
    array = band.ReadAsArray()  # crashes because dataset is deallocated (out of scope)

The following also crashes:

.. code-block:: python

    from osgeo import gdal
    fn = 'D:/tmp/girs/chirps_basin/chirps-v2.0.2016.01.10.tif'
    array = gdal.Open(fn, gdal.GA_ReadOnly).GetRasterBand(1).ReadAsArray()

Also this crashes:

.. code-block:: python

    band = RasterReader('D:/tmp/girs/chirps_basin/chirps-v2.0.2016.01.10.tif').get_band()
    array = band.ReadAsArray()

	
The following works: it does not return `band`, but what we want from the band, namely in this case the array.

.. code-block:: python


    from girs.rast.raster import RasterReader
    array = RasterReader('D:/tmp/girs/chirps_basin/chirps-v2.0.2016.01.10.tif').get_array()

.. note:: 

	Avoid using `get_band`