Fixed #25734 -- Made GDALBand min and max properties use GDALComputeRasterStatistics. (8f590456) · Commits · Dom Sekotill / django

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

+11 −2

Original line number	Diff line number	Diff line
		@@ -62,8 +62,17 @@ 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])
		get_band_minimum = double_output(std_call('GDALGetRasterMinimum'), [c_void_p, POINTER(c_int)])
		get_band_maximum = double_output(std_call('GDALGetRasterMaximum'), [c_void_p, POINTER(c_int)])
		get_band_statistics = void_output(std_call('GDALGetRasterStatistics'),
		[
		c_void_p, c_int, c_int, POINTER(c_double), POINTER(c_double),
		POINTER(c_double), POINTER(c_double), c_void_p, c_void_p,
		],
		errcheck=False
		)
		compute_band_statistics = void_output(std_call('GDALComputeRasterStatistics'),
		[c_void_p, c_int, POINTER(c_double), POINTER(c_double), POINTER(c_double), POINTER(c_double), c_void_p, c_void_p],
		errcheck=False
		)

		# Reprojection routine
		reproject_image = void_output(std_call('GDALReprojectImage'),

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

+77 −7

Original line number	Diff line number	Diff line
		from ctypes import byref, c_int
		import math
		from ctypes import byref, c_double, c_int, c_void_p

		from django.contrib.gis.gdal.base import GDALBase
		from django.contrib.gis.gdal.error import GDALException
		@@ -19,6 +20,14 @@ class GDALBand(GDALBase):
		self.source = source
		self._ptr = capi.get_ds_raster_band(source._ptr, index)

		def _flush(self):
		"""
		Call the flush method on the Band's parent raster and force a refresh
		of the statistics attribute when requested the next time.
		"""
		self.source._flush()
		self._stats_refresh = True

		@property
		def description(self):
		"""
		@@ -47,19 +56,80 @@ class GDALBand(GDALBase):
		"""
		return self.width * self.height

		_stats_refresh = False

		def statistics(self, refresh=False, approximate=False):
		"""
		Compute statistics on the pixel values of this band.

		The return value is a tuple with the following structure:
		(minimum, maximum, mean, standard deviation).

		If approximate=True, the statistics may be computed based on overviews
		or a subset of image tiles.

		If refresh=True, the statistics will be computed from the data directly,
		and the cache will be updated where applicable.

		For empty bands (where all pixel values are nodata), all statistics
		values are returned as None.

		For raster formats using Persistent Auxiliary Metadata (PAM) services,
		the statistics might be cached in an auxiliary file.
		"""
		# Prepare array with arguments for capi function
		smin, smax, smean, sstd = c_double(), c_double(), c_double(), c_double()
		stats_args = [
		self._ptr, c_int(approximate), byref(smin), byref(smax),
		byref(smean), byref(sstd), c_void_p(), c_void_p(),
		]

		if refresh or self._stats_refresh:
		capi.compute_band_statistics(*stats_args)
		else:
		# Add additional argument to force computation if there is no
		# existing PAM file to take the values from.
		force = True
		stats_args.insert(2, c_int(force))
		capi.get_band_statistics(*stats_args)

		result = smin.value, smax.value, smean.value, sstd.value

		# Check if band is empty (in that case, set all statistics to None)
		if any((math.isnan(val) for val in result)):
		result = (None, None, None, None)

		self._stats_refresh = False

		return result

		@property
		def min(self):
		"""
		Returns the minimum pixel value for this band.
		Return the minimum pixel value for this band.
		"""
		return capi.get_band_minimum(self._ptr, byref(c_int()))
		return self.statistics()[0]

		@property
		def max(self):
		"""
		Returns the maximum pixel value for this band.
		Return the maximum pixel value for this band.
		"""
		return self.statistics()[1]

		@property
		def mean(self):
		"""
		Return the mean of all pixel values of this band.
		"""
		return capi.get_band_maximum(self._ptr, byref(c_int()))
		return self.statistics()[2]

		@property
		def std(self):
		"""
		Return the standard deviation of all pixel values of this band.
		"""
		return self.statistics()[3]

		@property
		def nodata_value(self):
		@@ -84,7 +154,7 @@ class GDALBand(GDALBase):
		if not isinstance(value, (int, float)):
		raise ValueError('Nodata value must be numeric.')
		capi.set_band_nodata_value(self._ptr, value)
		self.source._flush()
		self._flush()

		def datatype(self, as_string=False):
		"""
		@@ -149,7 +219,7 @@ class GDALBand(GDALBase):
		else:
		return list(data_array)
		else:
		self.source._flush()
		self._flush()


		class BandList(list):

docs/ref/contrib/gis/gdal.txt

+43 −0

Original line number	Diff line number	Diff line
		@@ -1413,6 +1413,35 @@ blue.

		The total number of pixels in this band. Is equal to ``width * height``.

		.. method:: statistics(refresh=False, approximate=False)

		.. versionadded:: 1.10

		Compute statistics on the pixel values of this band. The return value
		is a tuple with the following structure:
		``(minimum, maximum, mean, standard deviation)``.

		If the ``approximate`` argument is set to ``True``, the statistics may
		be computed based on overviews or a subset of image tiles.

		If the ``refresh`` argument is set to ``True``, the statistics will be
		computed from the data directly, and the cache will be updated with the
		result.

		If a persistent cache value is found, that value is returned. For
		raster formats using Persistent Auxiliary Metadata (PAM) services, the
		statistics might be cached in an auxiliary file. In some cases this
		metadata might be out of sync with the pixel values or cause values
		from a previous call to be returned which don't reflect the value of
		the ``approximate`` argument. In such cases, use the ``refresh``
		argument to get updated values and store them in the cache.

		For empty bands (where all pixel values are "no data"), all statistics
		are returned as ``None``.

		The statistics can also be retrieved directly by accessing the
		:attr:`min`, :attr:`max`, :attr:`mean`, and :attr:`std` properties.

		.. attribute:: min

		The minimum pixel value of the band (excluding the "no data" value).
		@@ -1421,6 +1450,20 @@ blue.

		The maximum pixel value of the band (excluding the "no data" value).

		.. attribute:: mean

		.. versionadded:: 1.10

		The mean of all pixel values of the band (excluding the "no data"
		value).

		.. attribute:: std

		.. versionadded:: 1.10

		The standard deviation of all pixel values of the band (excluding the
		"no data" value).

		.. attribute:: nodata_value

		The "no data" value for a band is generally a special marker value used

docs/releases/1.10.txt

+5 −0

Original line number	Diff line number	Diff line
		@@ -74,6 +74,11 @@ Minor features
		* Added the :meth:`GEOSGeometry.covers()
		<django.contrib.gis.geos.GEOSGeometry.covers>` binary predicate.

		* Added the :meth:`GDALBand.statistics()
		<django.contrib.gis.gdal.GDALBand.statistics>` method and
		:attr:`~django.contrib.gis.gdal.GDALBand.mean`
		and :attr:`~django.contrib.gis.gdal.GDALBand.std` attributes.

		:mod:`django.contrib.messages`
		^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

tests/gis_tests/gdal_tests/test_raster.py

+50 −2

Original line number	Diff line number	Diff line
		@@ -310,14 +310,34 @@ class GDALBandTests(unittest.TestCase):
		self.band = rs.bands[0]

		def test_band_data(self):
		pam_file = self.rs_path + '.aux.xml'
		self.assertEqual(self.band.width, 163)
		self.assertEqual(self.band.height, 174)
		self.assertEqual(self.band.description, '')
		self.assertEqual(self.band.datatype(), 1)
		self.assertEqual(self.band.datatype(as_string=True), 'GDT_Byte')
		self.assertEqual(self.band.min, 0)
		self.assertEqual(self.band.max, 255)
		self.assertEqual(self.band.nodata_value, 15)
		try:
		self.assertEqual(
		self.band.statistics(approximate=True),
		(0.0, 9.0, 2.842331288343558, 2.3965567248965356)
		)
		self.assertEqual(
		self.band.statistics(approximate=False, refresh=True),
		(0.0, 9.0, 2.828326634228898, 2.4260526986669095)
		)
		self.assertEqual(self.band.min, 0)
		self.assertEqual(self.band.max, 9)
		self.assertEqual(self.band.mean, 2.8283266342289)
		self.assertEqual(self.band.std, 2.4260526986669)
		# Check that statistics are persisted into PAM file on band close
		self.band = None
		self.assertTrue(os.path.isfile(pam_file))
		finally:
		# Close band and remove file if created
		self.band = None
		if os.path.isfile(pam_file):
		os.remove(pam_file)

		def test_read_mode_error(self):
		# Open raster in read mode
		@@ -413,3 +433,31 @@ class GDALBandTests(unittest.TestCase):
		)
		else:
		self.assertEqual(bandmemjson.data(), list(range(25)))

		def test_band_statistics_automatic_refresh(self):
		rsmem = GDALRaster({
		'srid': 4326,
		'width': 2,
		'height': 2,
		'bands': [{'data': [0] * 4, 'nodata_value': 99}],
		})
		band = rsmem.bands[0]
		# Populate statistics cache
		self.assertEqual(band.statistics(), (0, 0, 0, 0))
		# Change data
		band.data([1, 1, 0, 0])
		# Statistics are properly updated
		self.assertEqual(band.statistics(), (0.0, 1.0, 0.5, 0.5))
		# Change nodata_value
		band.nodata_value = 0
		# Statistics are properly updated
		self.assertEqual(band.statistics(), (1.0, 1.0, 1.0, 0.0))

		def test_band_statistics_empty_band(self):
		rsmem = GDALRaster({
		'srid': 4326,
		'width': 1,
		'height': 1,
		'bands': [{'data': [0], 'nodata_value': 0}],
		})
		self.assertEqual(rsmem.bands[0].statistics(), (None, None, None, None))