django/tests/gis_tests/gdal_tests/test_raster.py

import os
import shutil
import struct
import tempfile

from django.contrib.gis.gdal import GDAL_VERSION, GDALRaster
from django.contrib.gis.gdal.error import GDALException
from django.contrib.gis.gdal.raster.band import GDALBand
from django.contrib.gis.shortcuts import numpy
from django.test import SimpleTestCase

from ..data.rasters.textrasters import JSON_RASTER


class GDALRasterTests(SimpleTestCase):
    """
    Test a GDALRaster instance created from a file (GeoTiff).
    """
    def setUp(self):
        self.rs_path = os.path.join(os.path.dirname(__file__), '../data/rasters/raster.tif')
        self.rs = GDALRaster(self.rs_path)

    def test_rs_name_repr(self):
        self.assertEqual(self.rs_path, self.rs.name)
        self.assertRegex(repr(self.rs), r"<Raster object at 0x\w+>")

    def test_rs_driver(self):
        self.assertEqual(self.rs.driver.name, 'GTiff')

    def test_rs_size(self):
        self.assertEqual(self.rs.width, 163)
        self.assertEqual(self.rs.height, 174)

    def test_rs_srs(self):
        self.assertEqual(self.rs.srs.srid, 3086)
        self.assertEqual(self.rs.srs.units, (1.0, 'metre'))

    def test_rs_srid(self):
        rast = GDALRaster({
            'width': 16,
            'height': 16,
            'srid': 4326,
        })
        self.assertEqual(rast.srid, 4326)
        rast.srid = 3086
        self.assertEqual(rast.srid, 3086)

    def test_geotransform_and_friends(self):
        # Assert correct values for file based raster
        self.assertEqual(
            self.rs.geotransform,
            [511700.4680706557, 100.0, 0.0, 435103.3771231986, 0.0, -100.0]
        )
        self.assertEqual(self.rs.origin, [511700.4680706557, 435103.3771231986])
        self.assertEqual(self.rs.origin.x, 511700.4680706557)
        self.assertEqual(self.rs.origin.y, 435103.3771231986)
        self.assertEqual(self.rs.scale, [100.0, -100.0])
        self.assertEqual(self.rs.scale.x, 100.0)
        self.assertEqual(self.rs.scale.y, -100.0)
        self.assertEqual(self.rs.skew, [0, 0])
        self.assertEqual(self.rs.skew.x, 0)
        self.assertEqual(self.rs.skew.y, 0)
        # Create in-memory rasters and change gtvalues
        rsmem = GDALRaster(JSON_RASTER)
        # geotransform accepts both floats and ints
        rsmem.geotransform = [0.0, 1.0, 2.0, 3.0, 4.0, 5.0]
        self.assertEqual(rsmem.geotransform, [0.0, 1.0, 2.0, 3.0, 4.0, 5.0])
        rsmem.geotransform = range(6)
        self.assertEqual(rsmem.geotransform, [float(x) for x in range(6)])
        self.assertEqual(rsmem.origin, [0, 3])
        self.assertEqual(rsmem.origin.x, 0)
        self.assertEqual(rsmem.origin.y, 3)
        self.assertEqual(rsmem.scale, [1, 5])
        self.assertEqual(rsmem.scale.x, 1)
        self.assertEqual(rsmem.scale.y, 5)
        self.assertEqual(rsmem.skew, [2, 4])
        self.assertEqual(rsmem.skew.x, 2)
        self.assertEqual(rsmem.skew.y, 4)
        self.assertEqual(rsmem.width, 5)
        self.assertEqual(rsmem.height, 5)

    def test_geotransform_bad_inputs(self):
        rsmem = GDALRaster(JSON_RASTER)
        error_geotransforms = [
            [1, 2],
            [1, 2, 3, 4, 5, 'foo'],
            [1, 2, 3, 4, 5, 6, 'foo'],
        ]
        msg = 'Geotransform must consist of 6 numeric values.'
        for geotransform in error_geotransforms:
            with self.subTest(i=geotransform), self.assertRaisesMessage(ValueError, msg):
                rsmem.geotransform = geotransform

    def test_rs_extent(self):
        self.assertEqual(
            self.rs.extent,
            (511700.4680706557, 417703.3771231986, 528000.4680706557, 435103.3771231986)
        )

    def test_rs_bands(self):
        self.assertEqual(len(self.rs.bands), 1)
        self.assertIsInstance(self.rs.bands[0], GDALBand)

    def test_memory_based_raster_creation(self):
        # Create uint8 raster with full pixel data range (0-255)
        rast = GDALRaster({
            'datatype': 1,
            'width': 16,
            'height': 16,
            'srid': 4326,
            'bands': [{
                'data': range(256),
                'nodata_value': 255,
            }],
        })

        # Get array from raster
        result = rast.bands[0].data()
        if numpy:
            result = result.flatten().tolist()

        # Assert data is same as original input
        self.assertEqual(result, list(range(256)))

    def test_file_based_raster_creation(self):
        # Prepare tempfile
        rstfile = tempfile.NamedTemporaryFile(suffix='.tif')

        # Create file-based raster from scratch
        GDALRaster({
            'datatype': self.rs.bands[0].datatype(),
            'driver': 'tif',
            'name': rstfile.name,
            'width': 163,
            'height': 174,
            'nr_of_bands': 1,
            'srid': self.rs.srs.wkt,
            'origin': (self.rs.origin.x, self.rs.origin.y),
            'scale': (self.rs.scale.x, self.rs.scale.y),
            'skew': (self.rs.skew.x, self.rs.skew.y),
            'bands': [{
                'data': self.rs.bands[0].data(),
                'nodata_value': self.rs.bands[0].nodata_value,
            }],
        })

        # Reload newly created raster from file
        restored_raster = GDALRaster(rstfile.name)
        # Presence of TOWGS84 depend on GDAL/Proj versions.
        self.assertEqual(
            restored_raster.srs.wkt.replace('TOWGS84[0,0,0,0,0,0,0],', ''),
            self.rs.srs.wkt.replace('TOWGS84[0,0,0,0,0,0,0],', '')
        )
        self.assertEqual(restored_raster.geotransform, self.rs.geotransform)
        if numpy:
            numpy.testing.assert_equal(
                restored_raster.bands[0].data(),
                self.rs.bands[0].data()
            )
        else:
            self.assertEqual(restored_raster.bands[0].data(), self.rs.bands[0].data())

    def test_nonexistent_file(self):
        msg = 'Unable to read raster source input "nonexistent.tif".'
        with self.assertRaisesMessage(GDALException, msg):
            GDALRaster('nonexistent.tif')

    def test_vsi_raster_creation(self):
        # Open a raster as a file object.
        with open(self.rs_path, 'rb') as dat:
            # Instantiate a raster from the file binary buffer.
            vsimem = GDALRaster(dat.read())
        # The data of the in-memory file is equal to the source file.
        result = vsimem.bands[0].data()
        target = self.rs.bands[0].data()
        if numpy:
            result = result.flatten().tolist()
            target = target.flatten().tolist()
        self.assertEqual(result, target)

    def test_vsi_raster_deletion(self):
        path = '/vsimem/raster.tif'
        # Create a vsi-based raster from scratch.
        vsimem = GDALRaster({
            'name': path,
            'driver': 'tif',
            'width': 4,
            'height': 4,
            'srid': 4326,
            'bands': [{
                'data': range(16),
            }],
        })
        # The virtual file exists.
        rst = GDALRaster(path)
        self.assertEqual(rst.width, 4)
        # Delete GDALRaster.
        del vsimem
        del rst
        # The virtual file has been removed.
        msg = 'Could not open the datasource at "/vsimem/raster.tif"'
        with self.assertRaisesMessage(GDALException, msg):
            GDALRaster(path)

    def test_vsi_invalid_buffer_error(self):
        msg = 'Failed creating VSI raster from the input buffer.'
        with self.assertRaisesMessage(GDALException, msg):
            GDALRaster(b'not-a-raster-buffer')

    def test_vsi_buffer_property(self):
        # Create a vsi-based raster from scratch.
        rast = GDALRaster({
            'name': '/vsimem/raster.tif',
            'driver': 'tif',
            'width': 4,
            'height': 4,
            'srid': 4326,
            'bands': [{
                'data': range(16),
            }],
        })
        # Do a round trip from raster to buffer to raster.
        result = GDALRaster(rast.vsi_buffer).bands[0].data()
        if numpy:
            result = result.flatten().tolist()
        # Band data is equal to nodata value except on input block of ones.
        self.assertEqual(result, list(range(16)))
        # The vsi buffer is None for rasters that are not vsi based.
        self.assertIsNone(self.rs.vsi_buffer)

    def test_offset_size_and_shape_on_raster_creation(self):
        rast = GDALRaster({
            'datatype': 1,
            'width': 4,
            'height': 4,
            'srid': 4326,
            'bands': [{
                'data': (1,),
                'offset': (1, 1),
                'size': (2, 2),
                'shape': (1, 1),
                'nodata_value': 2,
            }],
        })
        # Get array from raster.
        result = rast.bands[0].data()
        if numpy:
            result = result.flatten().tolist()
        # Band data is equal to nodata value except on input block of ones.
        self.assertEqual(
            result,
            [2, 2, 2, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 2, 2, 2]
        )

    def test_set_nodata_value_on_raster_creation(self):
        # Create raster filled with nodata values.
        rast = GDALRaster({
            'datatype': 1,
            'width': 2,
            'height': 2,
            'srid': 4326,
            'bands': [{'nodata_value': 23}],
        })
        # Get array from raster.
        result = rast.bands[0].data()
        if numpy:
            result = result.flatten().tolist()
        # All band data is equal to nodata value.
        self.assertEqual(result, [23] * 4)

    def test_set_nodata_none_on_raster_creation(self):
        if GDAL_VERSION < (2, 1):
            self.skipTest("GDAL >= 2.1 is required for this test.")
        # Create raster without data and without nodata value.
        rast = GDALRaster({
            'datatype': 1,
            'width': 2,
            'height': 2,
            'srid': 4326,
            'bands': [{'nodata_value': None}],
        })
        # Get array from raster.
        result = rast.bands[0].data()
        if numpy:
            result = result.flatten().tolist()
        # Band data is equal to zero because no nodata value has been specified.
        self.assertEqual(result, [0] * 4)

    def test_raster_metadata_property(self):
        data = self.rs.metadata
        self.assertEqual(data['DEFAULT'], {'AREA_OR_POINT': 'Area'})
        self.assertEqual(data['IMAGE_STRUCTURE'], {'INTERLEAVE': 'BAND'})

        # Create file-based raster from scratch
        source = GDALRaster({
            'datatype': 1,
            'width': 2,
            'height': 2,
            'srid': 4326,
            'bands': [{'data': range(4), 'nodata_value': 99}],
        })
        # Set metadata on raster and on a band.
        metadata = {
            'DEFAULT': {'OWNER': 'Django', 'VERSION': '1.0', 'AREA_OR_POINT': 'Point'},
        }
        source.metadata = metadata
        source.bands[0].metadata = metadata
        self.assertEqual(source.metadata['DEFAULT'], metadata['DEFAULT'])
        self.assertEqual(source.bands[0].metadata['DEFAULT'], metadata['DEFAULT'])
        # Update metadata on raster.
        metadata = {
            'DEFAULT': {'VERSION': '2.0'},
        }
        source.metadata = metadata
        self.assertEqual(source.metadata['DEFAULT']['VERSION'], '2.0')
        # Remove metadata on raster.
        metadata = {
            'DEFAULT': {'OWNER': None},
        }
        source.metadata = metadata
        self.assertNotIn('OWNER', source.metadata['DEFAULT'])

    def test_raster_info_accessor(self):
        if GDAL_VERSION < (2, 1):
            msg = 'GDAL ≥ 2.1 is required for using the info property.'
            with self.assertRaisesMessage(ValueError, msg):
                self.rs.info
            return
        infos = self.rs.info
        # Data
        info_lines = [line.strip() for line in infos.split('\n') if line.strip() != '']
        for line in [
            'Driver: GTiff/GeoTIFF',
            'Files: {}'.format(self.rs_path),
            'Size is 163, 174',
            'Origin = (511700.468070655711927,435103.377123198588379)',
            'Pixel Size = (100.000000000000000,-100.000000000000000)',
            'Metadata:',
            'AREA_OR_POINT=Area',
            'Image Structure Metadata:',
            'INTERLEAVE=BAND',
            'Band 1 Block=163x50 Type=Byte, ColorInterp=Gray',
            'NoData Value=15'
        ]:
            self.assertIn(line, info_lines)
        for line in [
            r'Upper Left  \(  511700.468,  435103.377\) \( 82d51\'46.1\d"W, 27d55\' 1.5\d"N\)',
            r'Lower Left  \(  511700.468,  417703.377\) \( 82d51\'52.0\d"W, 27d45\'37.5\d"N\)',
            r'Upper Right \(  528000.468,  435103.377\) \( 82d41\'48.8\d"W, 27d54\'56.3\d"N\)',
            r'Lower Right \(  528000.468,  417703.377\) \( 82d41\'55.5\d"W, 27d45\'32.2\d"N\)',
            r'Center      \(  519850.468,  426403.377\) \( 82d46\'50.6\d"W, 27d50\'16.9\d"N\)',
        ]:
            self.assertRegex(infos, line)
        # CRS (skip the name because string depends on the GDAL/Proj versions).
        self.assertIn("NAD83 / Florida GDL Albers", infos)

    def test_compressed_file_based_raster_creation(self):
        rstfile = tempfile.NamedTemporaryFile(suffix='.tif')
        # Make a compressed copy of an existing raster.
        compressed = self.rs.warp({'papsz_options': {'compress': 'packbits'}, 'name': rstfile.name})
        # Check physically if compression worked.
        self.assertLess(os.path.getsize(compressed.name), os.path.getsize(self.rs.name))
        # Create file-based raster with options from scratch.
        compressed = GDALRaster({
            'datatype': 1,
            'driver': 'tif',
            'name': rstfile.name,
            'width': 40,
            'height': 40,
            'srid': 3086,
            'origin': (500000, 400000),
            'scale': (100, -100),
            'skew': (0, 0),
            'bands': [{
                'data': range(40 ^ 2),
                'nodata_value': 255,
            }],
            'papsz_options': {
                'compress': 'packbits',
                'pixeltype': 'signedbyte',
                'blockxsize': 23,
                'blockysize': 23,
            }
        })
        # Check if options used on creation are stored in metadata.
        # Reopening the raster ensures that all metadata has been written
        # to the file.
        compressed = GDALRaster(compressed.name)
        self.assertEqual(compressed.metadata['IMAGE_STRUCTURE']['COMPRESSION'], 'PACKBITS',)
        self.assertEqual(compressed.bands[0].metadata['IMAGE_STRUCTURE']['PIXELTYPE'], 'SIGNEDBYTE')
        if GDAL_VERSION >= (2, 1):
            self.assertIn('Block=40x23', compressed.info)

    def test_raster_warp(self):
        # Create in memory raster
        source = GDALRaster({
            'datatype': 1,
            'driver': 'MEM',
            'name': 'sourceraster',
            'width': 4,
            'height': 4,
            'nr_of_bands': 1,
            'srid': 3086,
            'origin': (500000, 400000),
            'scale': (100, -100),
            'skew': (0, 0),
            'bands': [{
                'data': range(16),
                'nodata_value': 255,
            }],
        })

        # Test altering the scale, width, and height of a raster
        data = {
            'scale': [200, -200],
            'width': 2,
            'height': 2,
        }
        target = source.warp(data)
        self.assertEqual(target.width, data['width'])
        self.assertEqual(target.height, data['height'])
        self.assertEqual(target.scale, data['scale'])
        self.assertEqual(target.bands[0].datatype(), source.bands[0].datatype())
        self.assertEqual(target.name, 'sourceraster_copy.MEM')
        result = target.bands[0].data()
        if numpy:
            result = result.flatten().tolist()
        self.assertEqual(result, [5, 7, 13, 15])

        # Test altering the name and datatype (to float)
        data = {
            'name': '/path/to/targetraster.tif',
            'datatype': 6,
        }
        target = source.warp(data)
        self.assertEqual(target.bands[0].datatype(), 6)
        self.assertEqual(target.name, '/path/to/targetraster.tif')
        self.assertEqual(target.driver.name, 'MEM')
        result = target.bands[0].data()
        if numpy:
            result = result.flatten().tolist()
        self.assertEqual(
            result,
            [0.0, 1.0, 2.0, 3.0,
             4.0, 5.0, 6.0, 7.0,
             8.0, 9.0, 10.0, 11.0,
             12.0, 13.0, 14.0, 15.0]
        )

    def test_raster_warp_nodata_zone(self):
        # Create in memory raster.
        source = GDALRaster({
            'datatype': 1,
            'driver': 'MEM',
            'width': 4,
            'height': 4,
            'srid': 3086,
            'origin': (500000, 400000),
            'scale': (100, -100),
            'skew': (0, 0),
            'bands': [{
                'data': range(16),
                'nodata_value': 23,
            }],
        })
        # Warp raster onto a location that does not cover any pixels of the original.
        result = source.warp({'origin': (200000, 200000)}).bands[0].data()
        if numpy:
            result = result.flatten().tolist()
        # The result is an empty raster filled with the correct nodata value.
        self.assertEqual(result, [23] * 16)

    def test_raster_transform(self):
        # Prepare tempfile and nodata value
        rstfile = tempfile.NamedTemporaryFile(suffix='.tif')
        ndv = 99

        # Create in file based raster
        source = GDALRaster({
            'datatype': 1,
            'driver': 'tif',
            'name': rstfile.name,
            'width': 5,
            'height': 5,
            'nr_of_bands': 1,
            'srid': 4326,
            'origin': (-5, 5),
            'scale': (2, -2),
            'skew': (0, 0),
            'bands': [{
                'data': range(25),
                'nodata_value': ndv,
            }],
        })

        # Transform raster into srid 4326.
        target = source.transform(3086)

        # Reload data from disk
        target = GDALRaster(target.name)

        self.assertEqual(target.srs.srid, 3086)
        self.assertEqual(target.width, 7)
        self.assertEqual(target.height, 7)
        self.assertEqual(target.bands[0].datatype(), source.bands[0].datatype())
        self.assertAlmostEqual(target.origin[0], 9124842.791079799, 3)
        self.assertAlmostEqual(target.origin[1], 1589911.6476407414, 3)
        self.assertAlmostEqual(target.scale[0], 223824.82664250192, 3)
        self.assertAlmostEqual(target.scale[1], -223824.82664250192, 3)
        self.assertEqual(target.skew, [0, 0])

        result = target.bands[0].data()
        if numpy:
            result = result.flatten().tolist()

        # The reprojection of a raster that spans over a large area
        # skews the data matrix and might introduce nodata values.
        self.assertEqual(
            result,
            [
                ndv, ndv, ndv, ndv, 4, ndv, ndv,
                ndv, ndv, 2, 3, 9, ndv, ndv,
                ndv, 1, 2, 8, 13, 19, ndv,
                0, 6, 6, 12, 18, 18, 24,
                ndv, 10, 11, 16, 22, 23, ndv,
                ndv, ndv, 15, 21, 22, ndv, ndv,
                ndv, ndv, 20, ndv, ndv, ndv, ndv,
            ]
        )


class GDALBandTests(SimpleTestCase):
    rs_path = os.path.join(os.path.dirname(__file__), '../data/rasters/raster.tif')

    def test_band_data(self):
        rs = GDALRaster(self.rs_path)
        band = rs.bands[0]
        self.assertEqual(band.width, 163)
        self.assertEqual(band.height, 174)
        self.assertEqual(band.description, '')
        self.assertEqual(band.datatype(), 1)
        self.assertEqual(band.datatype(as_string=True), 'GDT_Byte')
        self.assertEqual(band.color_interp(), 1)
        self.assertEqual(band.color_interp(as_string=True), 'GCI_GrayIndex')
        self.assertEqual(band.nodata_value, 15)
        if numpy:
            data = band.data()
            assert_array = numpy.loadtxt(
                os.path.join(os.path.dirname(__file__), '../data/rasters/raster.numpy.txt')
            )
            numpy.testing.assert_equal(data, assert_array)
            self.assertEqual(data.shape, (band.height, band.width))

    def test_band_statistics(self):
        with tempfile.TemporaryDirectory() as tmp_dir:
            rs_path = os.path.join(tmp_dir, 'raster.tif')
            shutil.copyfile(self.rs_path, rs_path)
            rs = GDALRaster(rs_path)
            band = rs.bands[0]
            pam_file = rs_path + '.aux.xml'
            smin, smax, smean, sstd = band.statistics(approximate=True)
            self.assertEqual(smin, 0)
            self.assertEqual(smax, 9)
            self.assertAlmostEqual(smean, 2.842331288343558)
            self.assertAlmostEqual(sstd, 2.3965567248965356)

            smin, smax, smean, sstd = band.statistics(approximate=False, refresh=True)
            self.assertEqual(smin, 0)
            self.assertEqual(smax, 9)
            self.assertAlmostEqual(smean, 2.828326634228898)
            self.assertAlmostEqual(sstd, 2.4260526986669095)

            self.assertEqual(band.min, 0)
            self.assertEqual(band.max, 9)
            self.assertAlmostEqual(band.mean, 2.828326634228898)
            self.assertAlmostEqual(band.std, 2.4260526986669095)

            # Statistics are persisted into PAM file on band close
            rs = band = None
            self.assertTrue(os.path.isfile(pam_file))

    def test_read_mode_error(self):
        # Open raster in read mode
        rs = GDALRaster(self.rs_path, write=False)
        band = rs.bands[0]

        # Setting attributes in write mode raises exception in the _flush method
        with self.assertRaises(GDALException):
            setattr(band, 'nodata_value', 10)

    def test_band_data_setters(self):
        # Create in-memory raster and get band
        rsmem = GDALRaster({
            'datatype': 1,
            'driver': 'MEM',
            'name': 'mem_rst',
            'width': 10,
            'height': 10,
            'nr_of_bands': 1,
            'srid': 4326,
        })
        bandmem = rsmem.bands[0]

        # Set nodata value
        bandmem.nodata_value = 99
        self.assertEqual(bandmem.nodata_value, 99)

        # Set data for entire dataset
        bandmem.data(range(100))
        if numpy:
            numpy.testing.assert_equal(bandmem.data(), numpy.arange(100).reshape(10, 10))
        else:
            self.assertEqual(bandmem.data(), list(range(100)))

        # Prepare data for setting values in subsequent tests
        block = list(range(100, 104))
        packed_block = struct.pack('<' + 'B B B B', *block)

        # Set data from list
        bandmem.data(block, (1, 1), (2, 2))
        result = bandmem.data(offset=(1, 1), size=(2, 2))
        if numpy:
            numpy.testing.assert_equal(result, numpy.array(block).reshape(2, 2))
        else:
            self.assertEqual(result, block)

        # Set data from packed block
        bandmem.data(packed_block, (1, 1), (2, 2))
        result = bandmem.data(offset=(1, 1), size=(2, 2))
        if numpy:
            numpy.testing.assert_equal(result, numpy.array(block).reshape(2, 2))
        else:
            self.assertEqual(result, block)

        # Set data from bytes
        bandmem.data(bytes(packed_block), (1, 1), (2, 2))
        result = bandmem.data(offset=(1, 1), size=(2, 2))
        if numpy:
            numpy.testing.assert_equal(result, numpy.array(block).reshape(2, 2))
        else:
            self.assertEqual(result, block)

        # Set data from bytearray
        bandmem.data(bytearray(packed_block), (1, 1), (2, 2))
        result = bandmem.data(offset=(1, 1), size=(2, 2))
        if numpy:
            numpy.testing.assert_equal(result, numpy.array(block).reshape(2, 2))
        else:
            self.assertEqual(result, block)

        # Set data from memoryview
        bandmem.data(memoryview(packed_block), (1, 1), (2, 2))
        result = bandmem.data(offset=(1, 1), size=(2, 2))
        if numpy:
            numpy.testing.assert_equal(result, numpy.array(block).reshape(2, 2))
        else:
            self.assertEqual(result, block)

        # Set data from numpy array
        if numpy:
            bandmem.data(numpy.array(block, dtype='int8').reshape(2, 2), (1, 1), (2, 2))
            numpy.testing.assert_equal(
                bandmem.data(offset=(1, 1), size=(2, 2)),
                numpy.array(block).reshape(2, 2)
            )

        # Test json input data
        rsmemjson = GDALRaster(JSON_RASTER)
        bandmemjson = rsmemjson.bands[0]
        if numpy:
            numpy.testing.assert_equal(
                bandmemjson.data(),
                numpy.array(range(25)).reshape(5, 5)
            )
        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))

    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)

    def test_band_data_replication(self):
        band = GDALRaster({
            'srid': 4326,
            'width': 3,
            'height': 3,
            'bands': [{'data': range(10, 19), 'nodata_value': 0}],
        }).bands[0]

        # Variations for input (data, shape, expected result).
        combos = (
            ([1], (1, 1), [1] * 9),
            (range(3), (1, 3), [0, 0, 0, 1, 1, 1, 2, 2, 2]),
            (range(3), (3, 1), [0, 1, 2, 0, 1, 2, 0, 1, 2]),
        )
        for combo in combos:
            band.data(combo[0], shape=combo[1])
            if numpy:
                numpy.testing.assert_equal(band.data(), numpy.array(combo[2]).reshape(3, 3))
            else:
                self.assertEqual(band.data(), list(combo[2]))