Fixed #26415 -- Allowed deleting nodata value on GDALBands.

django/contrib/gis/gdal/prototypes/raster.py

@@ -62,6 +62,10 @@ get_band_ds = voidptr_output(std_call('GDALGetBandDataset'), [c_void_p])
 get_band_datatype = int_output(std_call('GDALGetRasterDataType'), [c_void_p])
 get_band_nodata_value = double_output(std_call('GDALGetRasterNoDataValue'), [c_void_p, POINTER(c_int)])
 set_band_nodata_value = void_output(std_call('GDALSetRasterNoDataValue'), [c_void_p, c_double])
+if GDAL_VERSION >= (2, 1):
+    delete_band_nodata_value = void_output(std_call('GDALDeleteRasterNoDataValue'), [c_void_p])
+else:
+    delete_band_nodata_value = None
 get_band_statistics = void_output(
     std_call('GDALGetRasterStatistics'),
     [

django/contrib/gis/gdal/raster/band.py

@@ -151,9 +151,14 @@ class GDALBand(GDALBase):
         """
         Sets the nodata value for this band.
         """
-        if not isinstance(value, (int, float)):
-            raise ValueError('Nodata value must be numeric.')
-        capi.set_band_nodata_value(self._ptr, value)
+        if value is None:
+            if not capi.delete_band_nodata_value:
+                raise ValueError('GDAL >= 2.1 required to delete nodata values.')
+            capi.delete_band_nodata_value(self._ptr)
+        elif not isinstance(value, (int, float)):
+            raise ValueError('Nodata value must be numeric or None.')
+        else:
+            capi.set_band_nodata_value(self._ptr, value)
         self._flush()
 
     def datatype(self, as_string=False):

docs/ref/contrib/gis/gdal.txt

@@ -1456,10 +1456,18 @@ blue.
         to mark pixels that are not valid data. Such pixels should generally not
         be displayed, nor contribute to analysis operations.
 
+        To delete an existing "no data" value, set this property to ``None``
+        (requires GDAL ≥ 2.1).
+
         .. versionchanged:: 1.9
 
             This property can now be set as well.
 
+        .. versionchanged:: 1.10
+
+            The "no data" value can now be deleted by setting the
+            ``nodata_value`` attribute to ``None``.
+
     .. method:: datatype(as_string=False)
 
         The data type contained in the band, as an integer constant between 0

tests/gis_tests/gdal_tests/test_raster.py

@@ -48,6 +48,7 @@ import unittest
 from django.contrib.gis.gdal import HAS_GDAL
 from django.contrib.gis.gdal.error import GDALException
 from django.contrib.gis.shortcuts import numpy
+from django.test import SimpleTestCase
 from django.utils import six
 from django.utils._os import upath
 
@@ -302,7 +303,7 @@ class GDALRasterTests(unittest.TestCase):
 
 
 @unittest.skipUnless(HAS_GDAL, "GDAL is required")
-class GDALBandTests(unittest.TestCase):
+class GDALBandTests(SimpleTestCase):
     def setUp(self):
         self.rs_path = os.path.join(os.path.dirname(upath(__file__)),
                                '../data/rasters/raster.tif')
@@ -467,3 +468,18 @@ class GDALBandTests(unittest.TestCase):
             'bands': [{'data': [0], 'nodata_value': 0}],
         })
         self.assertEqual(rsmem.bands[0].statistics(), (None, None, None, None))
+
+    def test_band_delete_nodata(self):
+        rsmem = GDALRaster({
+            'srid': 4326,
+            'width': 1,
+            'height': 1,
+            'bands': [{'data': [0], 'nodata_value': 1}],
+        })
+        if GDAL_VERSION < (2, 1):
+            msg = 'GDAL >= 2.1 required to delete nodata values.'
+            with self.assertRaisesMessage(ValueError, msg):
+                rsmem.bands[0].nodata_value = None
+        else:
+            rsmem.bands[0].nodata_value = None
+            self.assertIsNone(rsmem.bands[0].nodata_value)