Creating and modifying rasters
______________________________

Parameters used to create or copy rasters:

.. code-block:: python
    
    from girs.rast.raster import RasterReader
    r = RasterReader('D:/tmp/girs/chirps_basin/chirps-v2.0.2016.01.10.tif')
    rp = r.get_parameters()
    print rp.RasterXSize, rp.RasterYSize
    print rp.number_of_bands
    print rp.data_types
    print rp.geo_trans
    print rp.nodata
    print rp.srs
        
Copy
++++

.. code-block:: python

    from girs.rast.raster import RasterReader, copy
    r = RasterReader('D:/tmp/girs/chirps_basin/chirps-v2.0.2016.01.10.tif')
    # 1)  Using the function from file to file
    copy('D:/tmp/girs/chirps_basin/chirps-v2.0.2016.01.10.tif', 'D:/tmp/chirps-v2.0.2016.01.10.tif')
    r = RasterReader('D:/tmp/girs/chirps_basin/chirps-v2.0.2016.01.10.tif')
    # 2) Using the function from object to file
    copy(r, 'D:/tmp/chirps-v2.0.2016.01.10.tif')
    # 3) Using the method
    r.copy('D:/tmp/chirps-v2.0.2016.01.10.tif')
    # 4) Get a RAM copy
    r_mem = copy(r, '')
    print r_mem.get_parameters()
    # DIM[17, 13] NB[1] ND[-9999.0] DT[6] DRV[GTiff] SRS[WGS 84]
    # TRANS(-47.25, 0.25, 0.0, -18.0,... 0.0, -0.25)


Modify
++++++

RasterReader has not method to change data, although gdal dataset allows data editing also in read-only modus (without saving changes on disk). To change data, use ``RasterModifier`` or ``RasterWriter``.

.. code-block:: python

    from girs.rast.raster import RasterReader, RasterUpdate
    r = RasterUpdate('D:/tmp/girs/chirps_basin/chirps-v2.0.2016.01.10.tif')
    nodata = r.get_nodata()
    print 1, r.get_nodata()  # check data
    r.set_nodata(-8888.0)  # nodata = -8888.0, saved on disk

    r = RasterReader('D:/tmp/girs/chirps_basin/chirps-v2.0.2016.01.10.tif')
    print 2, r.get_nodata()  # check

    r = RasterUpdate('D:/tmp/girs/chirps_basin/chirps-v2.0.2016.01.10.tif')
    r.set_nodata(nodata)  # rollback

    r = RasterReader('D:/tmp/girs/chirps_basin/chirps-v2.0.2016.01.10.tif')
    print 3, r.get_nodata()  # check

Outputs::

    1 [-9999.0]
    2 [-8888.0]
    3 [-9999.0]


Write
+++++

.. code-block:: python

    import numpy as np
    import gdal
    from girs.rast.parameter import RasterParameters
    from girs.rast.raster import RasterWriter
    from girs.srs import srs_from_epsg
    columns, rows = 17, 13
    geotransformation = (-47.25, 0.25, 0.0, -18.0, 0.0, -0.25)
    srs = srs_from_epsg(4326).ExportToWkt()
    number_of_bands = 1
    nodata = 127
    data_types = gdal.GDT_Byte
    driver_short_name = 'GTiff'
    raster_parameters = RasterParameters(columns, rows, geotransformation, srs,
                                         number_of_bands, nodata, data_types, driver_short_name)
    r = RasterWriter(raster_parameters, source='D:/tmp/girs/write_example.tif')
    r.set_array(np.random.randint(128, size=(rows, columns)))
    r.show()
    
.. _trasterwriter:

.. figure:: images/rasterwriter2.jpg
    :width: 300pt